Japanese Knotweed - Not a weed to ignore!

Japanese Knotweed is a serious consideration for Lenders, Developers, Purchasers, Landowners, Planners and Surveyors. The impact of the discovery of Japanese Knotweed on land and buildings can prove to be significant.

Source: Charles Lyndon

Anyone who has a garden will be more than aware of the speed in which weeds will grow, which if left uncontrolled can become unsightly and overgrown very quickly. Having acquired an overgrown allotment a few years ago, which I spent many hours clearing and digging I can tell you with authority that weeds are almost impossible to eradicate and therefore need to be regularly controlled. Most varieties of weeds are harmless if regularly managed, with the exception of the odd thorny or irritant types of weeds. There is however one particular type of weed that has received increased publicity over recent years, due to the size and rate of growth. There are plenty of opinions in relation to the risk and the extent of damage that Japanese Knotweed can cause to buildings/structures and there are plenty of examples of people affected by it which has resulted in denial of mortgage applications, disputes with insurers and extensive costs in trying remove or control its growth. On the other side of the coin, recent research by AECOM challenges popular opinion and suggests ‘Japanese knotweed is no more of a threat to buildings than other plants’. The research of members of the Royal Institution of Chartered Surveyors (RICS) and the Property Care Association (PCA) who have interacted or dealt with Japanese Knotweed in one way or another found that ‘Only between 2% and 6% of respondents reported any co-occurrence of Japanese knotweed and structural damage to buildings. Our paper also concluded that where Japanese knotweed is associated with damage, it is likely that the plants will have exacerbated existing damage, rather than being the initial cause of the damage’. The results of the research are interesting and well worth a read; (Link).

Despite research by AECOM and others that suggest that Japanese is not the problem that the media would have us believe, we do live in a risk averse society. To those who buy/sell/rent and generally live in property I suspect that they will be un-swayed in their opinion and instead choose to panic at the mere mention of the words Japanese Knotweed in a similar way to which many people react to the words ‘Asbestos’ or ‘Subsidence’ etc. For those involved with property surveys and inspections it is essential to be able to identify Japanese Knotweed and to be able provide appropriate advice. This article is therefore written to provide some basic information about Japanese knotweed which can be used to supplement further reading.

Japanese Knotweed (Latin name - Fallopia japonica) was introduced into the UK as an ornamental plant by the Victorians. It originated from Asia in countries such as Northern China and Japan where it grew in harsh habitats on the slopes around volcanoes. When introduced into the UK the conditions were far more fertile than those in Asia allowing the plant to thrive. Japanese Knotweed is a Perennial Plant, meaning that it will grow for many seasons with the plant dying back in the winter and re-growing the following spring. Japanese Knotweed is capable of growing 10cm per day and it is highly invasive and capable of exposing weaknesses in buildings, foundations, concrete and tarmac. It has the capability of regenerating from minute rhizomes (a root or creeping stem), therefore there is a significant risk of spreading the plant from digging and other disturbance. Effective removal of Japanese Knotweed therefore requires a specialist, which as you would expect can be expensive.

As stated previously, Japanese Knotweed is a serious consideration for Lenders, Developers, Purchasers, Landowners, Planners and Surveyors. The impact of the discovery of Japanese Knotweed on land and buildings can prove to be significant. Land values can be reduced to take into account remediation works. It is therefore worth knowing how to identify Japanese Knotweed to firstly establish its presence and if identified how to deal with it. Devon County Council provided an excellent guide to the identification of Japanese Knotweed which is summarised below. The original link to the article is no longer active however the images and information below are still relevant:

How to identify Japanese Knotweed

  A Typical Japanese Knotweed Leaf

In the early spring red/purple shoots appear from the ground and grow rapidly forming canes. As the canes grow the leaves gradually open and turn green:

The plants are fully grown by early summer and mature canes are hollow with a distinctive purple speckle and form dense stands up to 3 metres high:

The plant flowers in late summer and these consist of clusters of spiky stems covered in tiny creamy-white flowers:

During the late autumn/winter the leaves fall and the canes die and turn brown. The canes remain standing throughout the winter and can often still be seen in new stands in the following spring and summer:

The rhizome is the underground part of the plant. It is knotty with a leathery dark brown bark and when fresh snaps like a carrot.  Under the bark it is orange or yellow.  Inside the rhizome is a dark orange/brown central core or sometimes it is hollow with an orange, yellow or creamy outer ring, although this is variable:

Japanese Knotweed and the Law

In 2016, the Environment Agency withdrew its Japanese Knotweed Code of Practice due to new government guidelines. This was replaced in March 2017, by the Invasive Non-Native Specialists Association (INNSA) new Code of Practice. Access to the new code is not as straightforward as the EA Code however you can request a copy from the following: (Link)

Below is a summary of the raft of legislation that relates to Japanese Knotweed which is taken from the Environment Agency’s Japanese Knotweed original Code of Practice.
  
Japanese Knotweed is classified as controlled waste and its disposal is strictly regulated. For example soil containing Japanese Knotweed roots/rhizomes is classified as contaminated waste and can only be taken to a licensed landfill site. Failure to dispose of Japanese Knotweed appropriately may lead to prosecution under section 34 of the Environmental Protection Act (EPA) 1990.  Also, although it is not a criminal offence to have Japanese Knotweed on your land, allowing it to grow onto neighbouring land may constitute a nuisance and as such may provide grounds for a civil action from those affected.

Other relevant legislation includes Section 14(2) of the Wildlife and Countryside Act 1981 states that '…if any person plants or otherwise causes to grow in the wild any plant which is included in Part II of Schedule 9, he shall be guilty of an offence'. Japanese knotweed is one of the plants listed in Schedule 9. Also, waste must be transferred to an authorised person, in other words a person who is either a registered carrier or exempted from registration by the Waste (England and Wales) Regulations 2011. A waste transfer note must be completed and signed giving a written description of the waste as per regulation 35 of the Waste Regulations. The Hazardous Waste Regulations 2005 contain provisions about the handling and movement of hazardous waste.

Japanese Knotweed continues to receive an increased amount of negative publicity which makes it increasingly important for those undertaking property surveys and inspections and giving property advice to be able to identify its presence and give appropriate and proportionate advice.  This article should serve as a good starting point and hopefully generate interest for further reading and research for built environment and related professions. 

Author: Gary O’Neill

Please feel free to share this article and other articles on this site with colleagues, friends and family who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Basement Construction - Part 2 – Waterproofing

Nobody will want to deal with water ingress into a basement, especially when construction is well advanced, or even worse when the basement is occupied and in use. It is therefore necessary to carefully select an appropriate water proofing system, as failure to carry out thorough investigations and careful design can prove disastrous and particularly expensive!

Source: http://www.northernvirginiabasementwaterproofing.com/

In my previous article I discussed the growing popularity of basement construction and highlighted a number of factors that require consideration during their design. Undoubtedly one of the most significant issues in relation basement construction is how to keep the internal environment dry and therefore exclude sub-surface water. The impact of water and particularly hydrostatic pressure was highlighted: ‘Water in the ground has the ability to exert a lot of force onto the structure of the basement depending on the head or height of the water. This is something known as hydrostatic pressure. This is better defined as ‘the pressure at a point in a fluid at rest due to the weight of the fluid above it’. Basement design therefore needs to take into account the height of the water table because that will influence the amount of hydrostatic pressure that a basement structure will be exposed to. The method of waterproofing will also need to be designed to consider hydrostatic pressure’.

Nobody will want to deal with water ingress into a basement, especially when construction is well advanced, or even worse when the basement is occupied and in use. It is therefore necessary to carefully select an appropriate water proofing system, as failure to carry out thorough investigations and careful design can prove disastrous and particularly expensive! There are many specialist companies and waterproofing products on the market who offer a variety of different solutions for dealing with water ingress into basements however for the purposes of this article I will provide examples of a number of well established methods of basement waterproofing. Selection will vary depending on factors, such as ground conditions, the height of the water table, the method of basement construction, the proposed use of a basement and as ever, cost.

Source: http://quality-waterproofing.com/

When considering an appropriate way of waterproofing a new basement it is advisable to review the recommendations within BS8102:2009 ‘Code of Practice for Protection of Below Ground Structures Against Water from the Ground’. The standard advises on the types of waterproofing available and confirms the performance grade to be achieved:

Type of Waterproofing:

Type A (Barrier) protection - A barrier to water ingress is applied to the inner or outer surface of the structure

Type B (Structurally Integral) Protection - The structure is formed as a watertight construction and requires no additional protection

Type C (Drained) Protection - Water entering the structure is received by planned cavities or voids and safely removed

Grades of Waterproofing Protection:

Grade 1 - Some water seepage and damp is tolerable depending on the intended use. Car parking, plant rooms etc.

Grade 2 - No water penetration is acceptable. Damp areas are tolerable depending on the end use. Plant rooms, workshops etc.

Grade 3 - No dampness or water penetration is acceptable - Ventilated residential and commercial

Type A (Barrier) Protection relies totally on a waterproofing membrane to keep water permanently out of the internal basement environment. Concrete and blockwork are typical examples of materials used in basement construction, however these materials are highly porous, particularly in concealed enclosed environments such as below ground. Masonry materials have the ability to absorb high volumes of water, which once saturated will seep through to the internal environment. Barrier protection, often referred to as tanking is a method which prevents water saturating through the basement wall with the provision/application of an impervious membrane to the internal or external face of the wall. Tanking can also be provided within the structure, something referred to as sandwich tanking, although this method is less commonly used.

In my early years working as a labourer for a ground works Contractor, I remember a particularly project where I was required to paint the external face of a number of in-situ concrete constructed lift shafts, at their bases, with a liquid bitumen paint, which was referred to as ‘black jack’. At the time, I never really understood why it was necessary to paint concrete walls that were going to be buried in the ground, until someone explained that what I was doing was providing waterproofing protection.

Nowadays there are many products on the market in the form of brush applied surface coverings, trowel applied renders and rolled sheet applied materials such as elastomeric which are used for tanking solutions for basements. The success of a tanking method will be determined by the selection of the correct method as well as the quality of the installation. Many tanking solutions require installation by approved contractors and although these systems may seem expensive, it is worth considering the likely disruption and excessive cost of trying to rectify water ingress to a basement when it is occupied!

Type B (Structurally Integral) Protection relies on the basement structure itself to be robust enough to resist water ingress. In most cases the external basement structure will be constructed with concrete which must be designed to minimise joints as well as being cast with plenty of reinforcement to reduce the risk of cracking. It is not uncommon for concrete basements designed to achieve structural integral protection to include additional waterproofing measures to provide a barrier against water and water vapour. This may include the introduction of waterproofing admixtures into the concrete mix in order to help reduce porosity and drying shrinkage.

Structural integral protection will nearly always have a cooler internal surface temperature compared to other forms of waterproofing and such will be more prone to the effects of condensation. It is therefore necessary to additionally consider control of atmospheric moisture with the possible installation of controlled ventilation fans and de-humidifiers.  Clearly the design solution will depend upon grade and proposed use of the basement and additional measures may not be required in all situations

Type C (Drained) Protection takes the view that some water will be allowed through the external basement structure, however it will be dealt with or controlled when it arrives.  Drained protection may be a possibility in heavily waterlogged ground, possibly with a high water table or where for other reasons it will prove difficult to prevent moisture entering into an internal basement environment.  Any water that enters into the basement is gathered and disposed of in an appropriate way.

Drained protection usually takes the form of a raised floor and an additional membrane or wall installed/constructed in front of the main basement structure with a small cavity in between. Any water that finds its way through the main basement wall will seep behind the cavity (wall and floor), where through design the water will be channelled to a sump, which is basically a low point that will collect water, which is then usually pumped away from the basement.  Internally, there may be water entering the basement but this is concealed within the cavity. Therefore the internal basement environment remains dry.

As you would expect there are a number of disadvantages with the use of drained protection: Due to the installation of as wall and floor cavity there could be a loss in floor to ceiling height and useable space and pumps will need regular maintenance. There is also a possibility that high hydrostatic pressure will result in excessive amounts of water through the basement structure, which may not be able to be effectively drained. This will however be avoided with suitable design.

It is clear that waterproofing of a basement takes careful consideration, where the method of waterproofing should be determined by the range of different factors discussed above. Failure to understand ground conditions, including the impact of water in the ground, together other site conditions/restraints may result in the selection of a waterproofing system that is not fit for purpose. It is therefore always worth seeking specialist advice as remedial works will often prove to be very expensive.

Author: Gary O’Neill

Please feel free to share this article and other articles on this site with colleagues, friends and family who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Basement Construction - Part 1 - Design Considerations

When considering whether to construct a basement it is first worth weighing up the advantages and disadvantages, and then also thinking about a number of design considerations which will undoubtedly impact on the construction method, waterproofing, safety, usability and ultimately, costs

Source:Homebuilding & Renovating

An article in the London Evening Standard from 2013 (link) highlighted the growing popularity of basement construction, particularly where land is at a premium or restricted above ground. The scale of the proposed basement construction in the article was extensive to a point where it generated a section 106 contribution of £825,000!:

A millionaire hedge fund boss digging out a basement eight times the size of a typical London home has been ordered to pay £825,000 towards affordable housing in his area.
Kensington & Chelsea council planners said the two-storey, 9,160sq?ft basement — complete with cinema room, swimming pool and whirlpool spa — is the biggest they have been asked to approve. The scale of the extension, below two large Notting Hill villas which have been turned into a single family home, means it has fallen foul of rules that normally apply only to major commercial developments.

The fashion for digging out super-size basements to create so-called ‘iceberg homes’ in London, and the prospect of years of disturbance during excavation, has pitted residents against each other in some streets ......... neighbours are said to be horrified by the scale of the works which will involve scores of lorry loads of earth being removed from the site. One said: “It will certainly be one of the ‘iceberg houses’ and sadly, our house will probably be the Titanic.” The number of applications for subterranean spaces in Kensington & Chelsea has soared in recent years.......

Although the news article identified above is a rather extreme example of a residential basement construction it does demonstrate an alternative way of providing valuable useable space when above ground construction may be restricted or unavailable. Basement construction is still considered a less conventional method of adding space compared to above ground construction and is often instigated by those who are prepared to challenge the conventional norm and think outside the box. There are however many examples of residential buildings throughout the UK where basements were constructed as a normal part of the building process. Houses built during the Victorian period provide a typical example of where basements were commonly constructed and nowadays, these Victorian basements are often converted and refurbished to made them part of the useable habitable space within a dwelling.

When considering whether to construct a basement it is first worth weighing up the advantages and disadvantages, and then also thinking about a number of design considerations which will undoubtedly impact on the construction method, waterproofing, safety, usability and ultimately, costs.

Source: Source: http://basementwaterproof.com/

Clearly basements can add space and value to a property and it could also be argued that security can be less of an issue as there will be less accessible entry points into a basement, as by its very nature the structure in buried in the ground. Also, as long as the basement is waterproofed appropriately (something I will be discussing in my next article), and insulated correctly, you could argue that a basement can be made energy efficient more readily that an above ground building. Conversely, the perceived disadvantages and the impact that these may have on costs will prevent a lot of people proceeded beyond the initial enquiry stage when considering basement construction.

One of the key things to consider is that by placing an enclosed structure such as a basement in the ground you are subjecting the structure to a number of different forces. The first is the presence of water in the ground. Water is a naturally occurring element in the ground and the level of this water will vary from location to location. Many will be familiar with the term ‘water table’ which can be understood as the layer below which the ground is completely filled up (or saturated) with water. Try to imagine a basement like a boat which is surrounded by water in the ground. The problem is that boats leak, and so do basements!  A basement is unlikely to sink like a boat, but because the basement is an enclosed structure it has the ability to hold a lot of water if the basement is not adequately waterproofed. Water in the ground also has the ability to exert a lot of force onto the structure of the basement depending on the head or height of the water. This is something known as hydrostatic pressure.  This is better defined as ‘the pressure at a point in a fluid at rest due to the weight of the fluid above it’. Basement design therefore needs to take into account the height of the water table because that will influence the amount of hydrostatic pressure that a basement structure will be exposed to.  The method of waterproofing will also need to be designed to consider hydrostatic pressure.

In order to design and construct a basement correctly it is first necessary to establish ground conditions. This will require a thorough ground investigation which although will have a cost attached to it, is essential at the very early stages of a project. This will also highlight the type of ground and any contaminants present together with information of water in the ground and importantly the height of the water table. Other design considerations will include; protection and stability to adjacent structures, basement depth, boundary issues including Party Wall etc. Act implications, method of excavation, temporary support, method of construction in addition to exclusion of ground water. Of course all of this will have an impact on costs and there is no getting away from the fact that constructing a basement can be very expensive.

In my next article I will consider a number of methods of waterproofing of basements and explain that the correct choice of which method to use is crucial to ensure that the internal environment within a basement remains dry.

Author: Gary O’Neill

Please feel free to share this article and other articles on this site with colleagues, friends and family who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Dry Rot – An ‘Intelligent’ Fungus requiring intelligent diagnosis

The reason that dry rot is often so devastating is because of its ability to travel long distances as it searches for more and more timber to remove moisture from

Source: Dynamic Property Care UK

As a Building Surveyor there are certain words that you know, just by saying them will strike fear and panic into the majority of members of the public. Words such as subsidence or asbestos are examples, which regularly appear in the news due to significant cost or health implications. In many cases however, potential subsidence or the identification of asbestos often result in relatively simple and cost effective solutions although it seems to be a natural human reaction to automatically think the worst. The ‘term’ dry rot is also generally well known by members of the public, however unlike subsidence and asbestos the implications of the discovery of dry rot is more often than not serious, depending upon the stage at which it is actually identified.

I was recently watching a well know property renovation programme on TV a few weeks ago where the Presenter had identified what looked to be dry rot on the ground floor of semi-detached three-bedroom residential property. Although, I agree that what he was looking at did appear to be dry rot, his description included, ‘feeding off concrete’ which is completely inaccurate as well as some of his terminology being confusing and wide of the mark. TV programmes should be mindful of the information that they provide, as it is possible, dare I say likely, (just by the nature of the amount of viewers), that someone will act on what they are being told which could result in loss/damage. In order to identify if or where dry rot may be present, it is useful to understand the conditions that dry rot needs to grow and thrive.

Dry rot is a fungus, often referred to as an ‘intelligent fungus’. The reason dry rot is referred to as intelligent is because of its ability to travel across non-timber surfaces and to take moisture from timber. What is left behind is dry friable timber that can easily be broken up with moderate hand pressure.  The reason that dry rot is often so devastating is because of its ability to travel long distances as it searches for more and more timber to remove moisture from. It is worth noting that when the dry rot fungus travels across non-timber surfaces such as bricks, mortar, concrete etc. it is just using these as a route or bridge to find other timber. Dry rot does not ‘feed’ off these types of surfaces but carries moisture with it in strands which allows it to grow and spread. If left untreated dry rot has the ability to affect vast amounts of timber within a building, often resulting in extensive specialist remedial works which are not cheap to deal with.

Dry rot is a living fungus which will continue to grow by feeding off timber, which it will completely destroy be removing all of its moisture. Without being too technical, there are four primary stages in the dry rot lifecycle. The first stage is Spores. The spores are constantly present in the atmosphere however are only activated in certain conditions, which require timber and moisture. For dry rot to thrive its ideal environment will include timber with a moisture content of between 22% and 25%, warm humid temperatures of between 240 and 300, poorly ventilated areas and dark concealed spaces. This is why dry rot will often spread undetected in basements, floor voids, roof voids, behind plasterboard in timber stud walls and the like. As the spores start to become more concentrated they develop into small white strands known as Hyphae, which look a little like small white cob-webs. These are reasonably easy to identify and a good indication of dry rot.

Source: Midas Property Developments

As the hyphae feeds off the timber it will extract further moisture from the timber as it continues to grow and become more concentrated in volume to a point where the hyphae mass develops into the next stage of the dry rot cycle, know as Mycelium. Visible large white mycelium strands can travel large distances in search of more timber and as previously stated can travel across non-timber surfaces in order to find new timber. In suitable conditions, mycelium will continue to exist and grow at a considerable rate within a building. Fungi prefers dark and damp areas with little or no air movement, therefore where these conditions change and threaten the fungus; its natural response is to create a Fruiting Body (Sporophore), and this is the final stage of the dry rot lifecycle. Visually the fruiting body can take a number of forms, however will generally appear in ‘mushroom like’ form. The fruiting body is the fungi's response to a threat to its survival and its reaction is to throw out spores into the air which can be transferred to other vulnerable areas within the building, which allows them to germinate and create a new attack of dry rot, thus restarting the dry rot life cycle right from the very beginning.

The dry rot lifecycle described above demonstrates how the fungus can spread so quickly and how much damage that can be caused if left undetected. It is possible to treat dry rot however this requires specialist knowledge and something that should not be attempted ‘on the cheap’.  If all traces of dry rot are not dealt with then all that will happen is the fungus will continue to grow and spread and start to affect any new timber that may have been installed. The steps below provide an indication of remedial works to deal with dry rot, however please bear in mind that this is indicative only and specialist advice should be sought in all situations:

1.   Deal with the moisture source
2.   Brush down any exposed masonry to remove visible surface fungal growth
3.   Deep-drill masonry at regular centres and irrigate with fungicidal wall solution
4.   Sterilise all exposed masonry surfaces with fungicidal wall solution
5.   Remove all affected timber including a minimum of 1m past the last identifiable location
6.   Dispose all affected timber from site
7.   Provide new treated and primed timber where previously removed
8.   Spray all new and adjacent timbers including cut ends with fungicidal spray
9.   Re-plaster where required using a cement and sand render mix
10. Ensure adequate ventilation is used

Dry Rot is easy to misdiagnose and I would always recommend that you engage the services of a professional such as a Building Surveyor for advice and guidance. Take a look at the excellent video below from Brick Tie Preservation.

Author: Gary O’Neill

Please feel free to share this article and other articles on this site with colleagues, friends and family who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the?copyright notice at the end of the blog.

Subsidence – Part 2 – Factors that contribute to subsidence

As with tree roots, a drainage system is buried therefore not obviously visible at the time of an inspection. It always amazes me how people tend to ignore the condition of the below ground drainage system when purchasing property and do not seem to see this as important

Source: Confused.com

In my last article I gave an example of the consequences of building subsidence, which can be extremely disruptive and expensive to deal with, however I also emphasised that the vast majority of subsidence damage is less serious and can be rectified reasonably easily. I also explained that to the average householder the mere mention of the word subsidence strikes fear and panic into them as there is a perception that subsidence damage is always serious. As you would expect and as I have mentioned many times before, if you are thinking of purchasing a property it is always advisable to have a professional, such as a Building Surveyor, inspect the building before you commit to buy. The Surveyor’s report will identify any issues that are present and inform you if any are serious. A Building Surveyor will also highlight factors that may contribute to subsidence in the future and not just focus on the here and now. There are a number of factors that could lead to subsidence and some examples are discussed below:

Clay Soils - To support a building it is essential that the load bearing capacity of the ground is capable of supporting the dead load of the building (the building’s self weight) as well as any imposed load (furniture, fitting, people, snow etc.), once completed and occupied. The type of ground is essential to a building’s stability as this will determine the most appropriate as well as the depth of the foundation that should be used. When siting a building, clay soils are particularly problematic compared to most other types of soil because clay has the ability for significant volumetric change depending on how much water/moisture it contains at any particular time. When clay is wet it will swell and therefore expand, however when the ground starts to dry out all of this moisture is slowly removed and the clay will shrink. Think about this process happening with a building on it!  If the ground is constantly expanding and then shrinking, then it is inevitable that the weight of a building will eventually be affected by these changes and cause the building to move. Having said the above there is no reason why a building cannot be constructed on clay as long as this is established through ground investigations and appropriately catered for in the design. This may involve deeper foundations, as well as the inclusion of root barriers where trees and vegetation may be in close proximity to the building.

Trees - Whilst inspecting a property, as well as focussing on the building itself I would always look very closely at the surrounding environment and in particular the size and location of trees. If not managed trees, and in particularly their roots have the ability to undermine foundations, damage drains and cause significant damage to a building. The problem with tree roots is that you often cannot see the extent of the root growth or proximity to the building because they are buried. This however does not mean that they should be ignored and where trees are deemed the pose a threat to a building then the services of a tree expert (Arboriculturist), should be called upon. This is necessary because different species of tree will exhibit different characteristic in terms of size, growth rate, root spread etc in addition to the advice that can be provided in respect of the condition of trees and any recommended remedial action.

Source: Absolute Plumbing and Drain Cleaning Services

Tree roots do a number of things when in the ground. Firstly, they take up large amounts of water. Given what has been discussed above in respect of clay soils you can easily see that in continued spells of warm weather and high temperatures that clay soil and tree roots are not a good combination and together this will significantly increase the potential for subsidence. Secondly, as the roots grow they have the ability to physically impact on soils, particularly the soft/granular types which can undermine their stability especially when they have a foundation and a building siting upon them.  Also, tree roots have the ability to damage below ground drainage.

Drainage - Although it is possible to make a broad assessment of a drainage system during an inspection by lifting manhole/inspection chamber covers this is limited to a small number of access points only and does not identify the condition of the vast majority of the drainage system around a building. As with tree roots, a drainage system is buried therefore not obviously visible at the time of an inspection. It always amazes me how people tend to ignore the condition of the below ground drainage system when purchasing property and do not seem to see this as important. Even if there is no visible indication of any issues with a drainage system it is still worth considering a CCTV inspection of the system is carried out.

Below ground drainage is quite vulnerable and can become damaged in a number of ways. Ground movement, even subtle movement can result in drains becoming displaced and fractured, particularly around the joints. Tree roots can also damage below ground drains and find their way into the system. If this type of damage does occur then the surface and foul water which is usually heading toward a sewer, will actually start to discharge at the point/s where the drainage is affected. If left undetected for a period of time then vast amounts of foul and surface water can be discharged into the ground around a building, which over time can start to influence the stability of the soil, which could eventually lead to ground movement. The lesson here is always establish the condition of the below ground drainage system and deal with any problems quickly, before they become much more serious.

Adjacent Excavations - A building could sit quite happily for many years on stable ground without any problems and will only be affected if for some reason the ground conditions change. One way this could happen is works being carried out in close proximity to a building that requires excavations. If excavations are carried out to a depth and distance that could undermine or influence the stability of another building then this can cause movement, sometimes, sudden movement. This should be considered in design where it may be necessary to provide temporary support. I have encountered this on numerous occasions where ground movement has been caused by a neighbour excavating (usually foundations) and usually through ignorance has not considered the stability of their neighbours building.

Leaking Rainwater Goods (gutters and downpipes) - Even simple repair and maintenance tasks, if left unattended over a period of time can introduce large amounts of water into the ground, which can affect the soil and undermine foundations which can cause ground movement. Rainwater gutter and downpipe repairs are usually inexpensive however this is one of the most common defects that a Surveyor will encounter when carrying out inspections. Repairs to rainwater goods are usually inexpensive however if they are ignored and left for longer periods of time the consequential damage can be extensive and therefore much more expensive. The lesson here is to deal with routine maintenance and repairs sooner or pay the costs later! 

This article provides a quick overview of some of the factors that could contribute to subsidence. The points raised are not exhaustive (there are others) and you will note that no attempt has been made to discuss mining subsidence, which is a subject in its own right, perhaps for a future post.  

Author: Gary O’Neill

Please feel free to share this article and other articles on this site with colleagues, friends and family who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog. 

Subsidence – Part 1 – Not all it’s cracked up to be!

When you see cracking in a building it will not always be, in-fact is unlikely to be subsidence. This can only be established through a comprehensive building survey and detailed investigations

Source: Simply Business

As a Building Surveyor, when inspecting buildings I have learned over the years to be very cautious in the terminology I use in the presence of Clients because there are some words that just provoke panic. Take asbestos for example, or cracking or even subsidence. These words strike fear into many people mainly as a result of what they have seen in the news or read in the media. It is fair to say that sometimes these fears can be realised if any of the above examples are found to be present/occurring in a building, however in the vast majority of cases, these issues can be dealt with relatively easily. This is generally a result of a lack of real understanding, which is why it is always advisable to seek professional advice from a Building Surveyor or other relevant professionals.

When I first graduated from University I joined a Property Consultancy who’s main area of business was dealing with subsidence insurance claims as Loss Adjusters. My role was to visit site with a more experienced Structural Engineer, who would make an initial assessment, and then I would be required to manage the claim to a conclusion. This often involved crack monitoring to establish whether any movement was historic (had now stopped) or progressive (was still continuing). This was a crucial part of the process as it is pointless dealing with the effect of subsidence until movement has been stopped. On the occasions where movement was found to be progressive, it was sometimes first necessary to undertake substantial remedial work such as underpinning to stabilise the building. In these instances, the whole process could be lengthy and disruptive for the residents and in some cases required temporarily decanting of the occupants to alternative accommodation for the duration of the works. Most home insurance policies will cover subsidence risk and incorporate an excess payment in the region of £1000 (always check the wording of your policy because there can be variations). This demonstrates that the effects of subsidence can be disruptive and even though it may be covered by home insurance it can still be expensive.

Source: own

The above scenario provides an example of what can happen at one end of the scale, however as already stated the vast majority of subsidence claims I managed were dealt with quickly and with minimal disruption, many proving not to be subsidence at all. When undertaking building surveys, a Surveyor will not just identify where and why subsidence has occurred, but also look for indicators that may contribute to subsidence in the future. Before providing you with details of what I would look for during a survey (this will be provided in part 2 of the article), I think it is important to first understand exactly what subsidence actually is.

Building design should involve careful consideration of the type/load of the building, the type of foundation used and ground bearing capacity and nature of the ground, the height of the water table and so on. These types of investigations should help to ensure that once the building is complete and occupied that it does not move!  Subsidence however is not the same as settlement. Settlement usually occurs in new or relatively new buildings. As buildings are very heavy they cause the ground to compact, although this will usually stop after a short period of time.  Also, most buildings are constructed in a variety of materials, all of which need to settle and in addition will have different rates of shrinkage.  Subsidence occurs when for some reason the load bearing capacity of the ground that a building is placed upon is no longer capable of accommodating that load. The reasons for the change is the load bearing capacity is impacted and this can occur for many different reasons and in some cases, many years after the building was first completed. It is quite feasible for a building to sit quite happily on a piece of ground for many years and due to some of the influences discussed it part 2 of this article, it can start to move.

Cracking in buildings occurs for many different reasons so it is fundamentally important that anyone who undertakes inspections or gives advice in respect of cracking should not make rash judgements and should gather all of the evidence before arriving at a possible cause. In order to aid the inspector, which as stated previously, can be a Building Surveyor, it might be necessary to recommend other investigations such as geo-technical surveys to establish ground type, composition, contaminants etc., trial holes to establish foundation depths, CCTV inspection of the drainage system and possibly an arboricultural survey to give advice on any trees that may be an influencing factor. The choice of which investigations are needed will be decided once the inspector has made an initial assessment of the cracking.  Therefore, when you see cracking in a building it will not always be, in-fact is unlikely to be subsidence however, this can only be established through a comprehensive building survey and detailed investigations.

In Part 2 of this article I will discuss subsidence in more detail and provide information of the things a Building Surveyor will look at to identify when and how subsidence is occurring as well as indicators that may suggest that subsidence can occur in the future.


Author: Gary O’Neill

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Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Stock Condition Surveys - Part 2 – A Consultant’s perspective

Above all, the success of a stock condition survey will be down to good organisation, management and leadership

Source: Spilled News

In my last article I discussed various reasons that may motivate a Client into undertaking a stock condition survey and identified a number of key factors that need to be considered prior to engaging a Consultant for delivery of the surveys.  In this article, after a brief explanation of how data capture has evolved over recent years, I want to view things from ‘the other side of the fence’ and discuss issues that a Consultant may encounter in both the pre and survey stages.

A short history of data capture

Over recent years technology had moved on at a rapid pace and there are now numerous hardware choices and software packages on the market that enable Surveyors to carry out surveys ‘remotely and in real time’. I have been lucky enough to be involved in stock condition surveys over the last 20 years, which initially were all undertaken on site by hand, usually with a pre-prepared proforma. This then developed into the first iteration of electronic data capture in the form Psion handheld’s. These were large ‘bulky’ pieces of equipment which were difficult to navigate through and were extremely limited in their capacity to store data. At the end of each day it was necessary to upload the information from the handheld via a docking station, which often led to ‘technical issues’ which sometimes resulted in data being lost.  As you can imagine this was very frustrating.  Battery life was also an issue, where it was necessary for us to take back up battery packs to allow us to stay on site for a full day. As technology advanced we started trialling on site data collection with smaller and slimmer PDA’s and Palm Pilots.  In the early days these were extremely ‘sluggish’ on site, as the capacity to store data was often limited. I can remember that one of my clients had produced a proforma that required recording of so many attributes that the PDA became unusable. We had to recommend a significant re-drafting of the proforma in order to be able to continue with the survey. Nowadays tablet’s have emerged as the new way of collecting on site data. These have built in camera’s, have much larger built in memories, are light weight and can offer unparalleled back up facilities. With a number of specialist stock survey software packages available we now have both hardware and software to make the whole process faster and more efficient. In addition, Cloud based technologies continue to evolve and these have significantly impacted on data storage and usability of data. It is however worth stating that however advanced hardware and software may become, the accuracy and value of the data will always be relative to the knowledge and expertise of the Surveyor.

Source: Journal for Clinical Studies

Pre-survey stage

It is highly unlikely that the cost of a stock condition survey will exceed OJEU thresholds (although after Brexit OJEU is unlikely to be an issue) therefore the content of a tender submission will be down to the requirements of each individual Client. At this stage it is vitally important to read the tender documents thoroughly to establish the scope of the survey and therefore assess the resources that will be needed to deliver what the client is expecting. Although very significant, resources will not just relate to the survey team.  Purchasing hardware and obtaining software licences can be extremely expensive which if not adequately considered could significantly reduce the profitability for the Consultant. Also, a Client may have their own in-house Asset Management system and if so are likely to require data collected during a stock condition survey to be compatible with their system. There are numerous examples of asset management software such as Orchard or Atrium to name a few, however a Consultant will need to become familiar with a Client’s particular system, which will involve consultation and possible training. In fact establishing a Client’s existing asset management processes and systems is fundamental to helping a Consultant to deliver a successful stock condition survey.

The deadline is also fundamentally important in planning the survey and also for fee calculation. A delivery programme should be formulated at the earliest possibly opportunity, working back from the Client’s deadline. The programme should include all pre and post survey activities including consultation with the Client; planning, pilot surveys, training of staff, arranging access, on site surveys, quality assurance checks, moderation and validation, reporting, etc. The amount of inspections that are required (which will be determined by the target sample size) will determine how many surveyors will be needed. It may be that during the preparation of the programme that a Consultant will realise they will need more surveyors than they first thought in order to achieve the deadline. This will subsequently impact on the amount of hardware and software licences that are needed and therefore the fee that is likely to be charged. 

Survey stage

Once a Consultant has been awarded a contract to deliver a stock condition survey there are number of things that can be done to ensure that the deadline is met and that the data collected in accurate and consistent:

Good leadership – It is extremely important that a Consultant appoints an experienced member of staff to oversee and take charge of the stock survey, right through to completion. Ideally, this individual should have been involved in the tender process and therefore understand the Client’s requirements; be able to manage a large team of surveyors and be able to incorporate and manage a robust quality assurance system and act as liaison with the Client. A Consultant should never underestimate the complexity of delivering a stock condition survey and unless a suitable ‘leader’ is appointed to manage the project, then the whole process can become chaotic and poorly managed and will ultimately result in failure.

Training – Quality of data and consistency are important in ensuring that the data can be confidently used in the future for a variety of different things.  Achieving this however is always one of the biggest challenges a Consultant will face and one of the biggest frustrations that a Client will encounter if the information received is of poor quality.  The problem with undertaking any inspection is that different surveyors could inspect exactly the same building but actually produce a different assessment of an element or an attribute.  This is human nature and although impossible to avoid, it is possible to manage.  What a Consultant should be trying to achieve is for Surveyors to be looking at elements/attributes in the same way and although they may not arrive at identical assessments, they should be very similar.

Prior to letting my Surveyors undertake the onsite surveys I would give then lots of information which would include definitions of physical condition, priority, user effect and risk rating etc. (This would vary from survey to survey, depending on the Client brief). The table below provides an example of typical definitions that could be used:

I would then arrange a half day workshop with the whole survey team, where amongst other things we would discuss the definitions and use examples to assess how individual Surveyors would consider a particular element/attribute. During this meeting we would also discuss and use the hardware/software that was going to be used for data collection, discuss access issues, time frames and the quality assurance procedure. These types of meeting are invaluable as it gives the survey team the opportunity to understand what is expected and provide an opportunity to raise any questions they may have.

Quality Assurance Procedures – As discussed throughout this article, quality assurance processes are an extremely important part of the whole process.  When managing large condition surveys I would spend a few days out on site with each member of the survey team during the first few weeks of the survey. This enabled my Surveyors to ‘iron out’ any uncertainties whilst I was present and to ask further questions as needed.  When the data was uploaded I was able to view this through the relevant asset management database and I was able to add filters so that I could generate numerous reports throughout the whole time that the data was being collected.  I was then able to question things that appeared to have been missed where data fields were empty, or ask questions where surveyors had identified high priority issues etc.  This enabled data to be corrected where necessary and sometimes identified surveyors who I needed to spend more time with who clearly required more training.

To consider every aspect of a stock condition survey in such a short article would be impossible.  Hopefully, I have discussed some interesting aspects of what can be a complex process to manage and deliver.  Above all, the success of a stock condition survey will be down to good organisation, management and leadership which will incorporate all of the various aspects I have discussed above.  Once the process is set up and organised correctly the data collection is usually reasonably straightforward. In order for this to be achieved there needs to be a great deal of planning and consultation many months before the data is collected onsite, if this is not undertaken then a Consultant is likely to encounter serious difficulties in meeting the expectations of their Client

Author: Gary O’Neill

Please feel free to share this article and other articles on this site with colleagues, friends and family 

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.