Japanese Knotweed - Not a weed to ignore!

The impact of the discovery of Japanese Knotweed on land and buildings can prove to be very significant.  Land values can be reduced to take into account remediation works, foundations, walls and other structures can be damaged in addition to the possible refusal of a mortgage.

Source: http://www.tpknotweed.com/

Anyone who is 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 recently acquired an overgrown allotment which I have 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 which is now deemed to be a threat to buildings and structures.  This weed has become such a risk that some mortgage lenders have refused mortgages when its presence has been identified. The culprit is Japanese Knotweed which in a recent article channel4.com/4homes (Online) (Link) states:

‘If you're buying a new home and Japanese knotweed comes up on the survey, a lender may refuse your mortgage. 'In practice, it's not usually a problem as long as a remediation plan is put in place,' says Sue Anderson, spokesperson for the Council of Mortgage Lenders (CML). 

It's clearly a worry for prospective home owners. 'We get 15 to 20 calls per week asking for advice on Japanese knotweed, often when a valuation for mortgage is made,' says Maxime Jay. 'The problem is that every mortgage lender has its own policy.'

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.  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 high 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.

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 very significant.  Land values can be reduced to take into account remediation works, foundations, walls and other structures can be damaged in addition to the possible refusal of a mortgage.  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 provide an excellent guide to the identification of Japanese Knotweed on their website (Link) which is summarises below:

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

There is a whole raft of different legislation that covers Japanese Knotweed and the summary below is taken from the Environment Agency’s Japanese Knotweed Code of Practice.  You read the Code of Practice in more detail from the following link (Link)

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.

In conclusion, Japanese Knotweed seems to be receiving an increased amount of negative publicity, however given the rate at which it grows, the damage and disruption it can cause and the costs involved in dealing with it, it is easy to see why!

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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.

Retaining Walls - Part 2 - Retaining Wall Construction Types

A retaining wall is not randomly constructed, but should be selected and designed to suit individual ground and site conditions

In last week’s article I provided some rather dramatic images of retaining wall failures and demonstrated that design and consequently selection of an appropriate construction method are crucial.  This is because there are many considerations that will affect the type, size and construction of a retaining wall which in most cases require the advice of a professional such as a Structural Engineer.  Finally I provided a graphic showing the many pressures/forces that occur behind a retaining wall which can significantly influence the stability of a retaining wall.  You can read my previous article from the following (Link 1).

Once thorough ground/site investigations have been completed there are a number of different types of retaining wall that may be selected. Basically, a retaining wall is not randomly constructed, but should be selected and designed to suit individual ground and site conditions.  There are various types of retaining solutions such as embedded retaining walls (e.g sheet piling) and reinforced soil walls, however, for the purposes of this article I plan to focus on gravity retaining walls (also known as mass retaining walls) which rely solely on their own weight to stand up and withstand all of the loads and pressures that they will be exposed to.  There a wide selection of gravity retaining wall solutions including Masonry (unreinforced), Concrete, (sometimes with masonry facing), Gabions and Crib retaining walls:

Masonry (unreinforced) Retaining Walls

These types of retaining wall are some of the earliest know retaining structures and are formed from masonry which has been mortared together. The lateral forces from backfill is resisted by the weight of wall itself, and due to their robust nature, they develop little or no tension.  Masonry retaining walls are not usually reinforced and are generally economical fro heights up to approximately three metres.

You will note from the image below from Chudley’s Building Construction handbook that a masonry retaining wall will need to incorporate weepholes positioned at approximately two metre centres in order to help relieve hydrostatic pressure.  Construction of a masonry retaining wall is generally labour intensive, often requiring deep excavation, temporary support, construction and backfilling.  Clearly this can provide significant safety issues, can be time consuming and often prove to be very expensive.

Source: Chudley R. & Greeno R (2005), Building Construction Handbook. Elsevier Butterworth Heinemann

Masonry Retaining Wall - Source: http://www.archiexpo.com/

Concrete Retaining Walls


Concrete retaining walls provide some flexibility in design as they allow wet concrete poured in-situ with the use of temporary timber formwork, or pre-cast concrete units to be used.  Mass concrete retaining walls will be designed using similar principles described above for masonry retaining walls and will have the same safety, labour and cost issues.  Concrete retaining walls are typically designed with a horizontal footing and a vertical stem wall. These types of retaining wall are referred to as Concrete Cantilever retaining walls. These walls allow a much thinner stem and therefore less construction material because the cross section of the wall is much thinner.  Concrete Cantilever walls utilize the weight of the backfill to provide most of the resistance to sliding and overturning, and because of this are economical up to heights of ten metres, much higher than the possibilities for unreinforced masonry retaining walls. The image below from Chudley’s Building Construction handbook details a section through a Concrete Cantilever wall where you will note how the backfill load applied to the horizontal footing will help to stabilise the wall.  The further image below also demonstrates how concrete pre-cast units can be used in addition to in-situ for Concrete Cantilever retaining walls.

Source: Chudley R. & Greeno R (2005), Building Construction Handbook. Elsevier Butterworth Heinemann

Pre-cast Concrete Retaining Wall - Source: http://groundtechgeo.com.au/

A slight variation to the Concrete Cantilever wall is the use/installation of Monolithic Counterforts. Counterfort walls are cantilever walls strengthened with counterforts monolithic with the back of the wall slab and base slab. The counterforts act as tension stiffeners and connect the wall slab and the base to reduce the bending and shearing stresses. Counterforts are used for high walls with heights greater than 8 to 12 m. They are also used for situations where high lateral pressures occur, e.g. where the backfill is heavily surcharged.

Pre-Cast Concrete Counterfort Retaining Wall - Source: http://designerpropertiestexas.com/

Gabions

Gabions are welded wire or rectangular wire mesh boxes, which are then filled with rock, and used for construction of erosion control structures and to stabilize steep slopes. Gabion design is based upon mass gravity design as detailed above and therefore relies on the mass and self weight of the Gabions to resist any imposed loads or forces. Stability is achieved through a combination of the self weight of the rocks and its interlocking and frictional strength.  Gabions are often constructed with stepped face and because of the voids between the rocks are able to more easily absorb forces by retained earth and flowing water.  Generally Gabions are more economical than other retaining structures as they require little maintenance, no skilled labour, minimum foundation preparation and no costly drainage systems.

Gabion Retaining Wall - Source: http://terraqua-es.co.uk/erosion-control/woven-gabions/

Crib Retaining Walls

Crib walls are made up of interlocking individual ‘boxes’ which are usually consist of timber or pre-cast concrete (see image below). Crushed stone or other coarse granular materials to create a free draining structure are used to fill the individual boxes.  Crib walls are popular because they are versatile, strong, light weight, cost effective, fast and easy to install.  Another advantage of crib walls, due to their form, is that they can be further enhanced within built geo-textile planters, allowing a faster "green up“ time than with other retaining solutions.  The advantage of using concrete instead of timber is that concrete components provide for long term durability and will not rot or warp, however the component cost is likely to be higher.

Timber Crib Retaining Wall - Source: http://www.geoforte.co.uk/

Concrete Crib Retaining Wall - Source: http://www.retainingsolutions.com.au/

I have provided an overview of typical types of retaining wall solutions above however there are numerous other engineering solutions than may be used depending upon ground conditions, loadings, location and the like.  In order to select an appropriate retaining wall, in most cases it will be necessary to seek professional advice, as the consequences of poor or inappropriate design can prove to be disastrous.

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

Retaining Walls - Part 1 – Spectacular Collapses!

Sudden retaining wall collapse is more often than not a result of the effect of forces/influences behind the wall and often inappropriate design

Retaining walls are an important feature in many construction projects, often a necessity, as they can provide a solution where land is uneven or sometimes at a significant gradient.  Very few construction sites are completely flat and where site levelling is not possible it may be necessary to consider retaining walls as a way of maximising development space, or solving access issues within or around a construction site.


Wordnetweb (Online) define a retaining wall as ‘a wall that is built to resist lateral pressure (especially a wall built to prevent the advance of a mass of earth)’. There are many considerations that will affect the type, size and construction of a retaining wall which in most cases require the advice of a professional such as a Structural Engineer.  This is because there are lots of pressures/forces occurring behind a retaining wall that can significantly influence the stability of a retaining wall.  The photographs below show the dramatic impact of what can happen when retaining walls fail: 

Source: wivinah-hefner.blogspot.co.uk

Source: Source: http://wqad.com/

Source: http://www.thestar.com.my/

Source: http://blogs.agu.org/

Source: http://www.nibiru-planetx.com/

Sudden retaining wall collapse will be a result of the effect of forces/influences behind the wall and often inappropriate design (See diagram below).  Not all damage to a retaining wall is as significant as the examples above and in fact much more subtle movement can occur over a long period of time before a retaining wall will eventually fail. It is therefore worth understanding the function of a retaining wall as well as the forces/influences that require consideration during design.

I published an article a few weeks ago on basement construction where I considered the influence of ground water and particularly hydrostatic pressure on the basement structure (Link).  This is also a significant factor when designing retaining walls, which if not controlled can effectively push against the internal face of the wall and cause it to fail. So in addition to all of the forces that will potentially affect a retaining wall, other factors for consideration will include the type and nature of the soil, the types of wall construction to be used, materials to be used in the wall construction, ease and speed of construction, the provision of expansion joints, health & safety issues and obviously cost!  As you can imagine there is an awful lot to think about and it is no surprise that professional advice may be needed.

In next week's article I will discuss retaining wall construction and consider different types of retaining wall.

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

UK Housing Market – ‘Help to Buy’ aiding recover or papering over the cracks?

For recovery to be sustainable it needs to be steady and measured.  Allowing people to borrow money, which they would not have been able to previously afford, to get the housing market moving may have a positive impact in the short term, but could prove to be a recipe for disaster in the future. 

Source: http://www.wiltshirebusinessonline.co.uk/

To describe the UK housing market as fickle would be an understatement.  Only 18 months ago the debate revolved around how to get the housing market moving, but after what appears to be a remarkable turnaround, there is now even talk about how to ‘cool’ the housing market!  In a recent article in the Guardian Online (Link), the Government cite their flagship Help to Buy scheme as the main driver for the recovery:

‘The government's controversial Help to Buy mortgage guarantee scheme has supported 7,313 home loans worth a total of £1bn since it was launched in October, official figures show.

The figures for the first six months of the mortgage scheme, released by the Treasury, showed the mean value of a property purchased or remortgaged through the scheme was £151,597, well below the average house price of £252,000 recorded by the Office for National Statistics.

The Treasury said 80% of the supported loans were given to first-time buyers and claimed a larger proportion of the market was being helped outside London and the south-east.

Commenting on the figures, and data showing that more than 20,000 people have bought newbuild homes through the separate equity loan scheme, the prime minister, David Cameron, said his government had helped both buyers and builders’

Source: http://blog.sewellgardner.com/

In order to use the first part of the Help to Buy scheme borrowers will first need to save a deposit of 5% of the value of the property they want to purchase.  They will then be able to apply for an interest free loan for a further 20% of the value of the property, to a maximum loan value of £120,000. Repayment of the loan will then be made when the property is eventually sold. After five years the loan will start to attract what the government call a ‘fee’, which is basically interest at a rate 1.75% which will increase annually thereafter by the current Retail Price Index inflation plus 1%.  The loan is therefore interest free, but you need to read the small print to see that this only applies for five years.

There is no doubt that the Help to Buy scheme has brought buyers to the market sooner than they would have been able to without the scheme, however, let us look into our crystal ball and see what could happen over the next few years.

Firstly, interests rates WILL rise!  The question is actually when, not if. I am sure that those with mortgages, like myself are monitoring the news very closely and in particular noises coming from the Bank of England.  Some commentators suggest that this may happen toward the end of this year, other suggest early 2015. Over recent years mortgage borrowers have been spoilt by a record low base rate of just 0.5%.  Although the property market has suffered with the economy, we have had the opportunity to borrow money very cheaply for many years. Those who have taken this opportunity may have been lulled into a false sense of security, hoping that this will last for the vast duration of their mortgage loan!  In reality however, it is likely that those who have stretched their budgets or maybe those who are new to the property market will find any interest rate increase a major shock to their finances.  The outcome is that many may find themselves in a position where they will struggle to meet their loan re-payments and unfortunately others are likely to lose their homes.

Also, as explained above, after five years the help to buy loan will start to attract a fee, which if added to rising interest rates is going to impact significantly, particularly those at the lower end of the income scale.  This therefore begs the question, is the help to buy scheme aiding recover or is it just papering over the cracks?  I am sure that lenders will tell us that they have robust audit procedures to ensure that lenders are able to payback their loans, however Reuters (Online) (Link) recently reported: ‘Economic recovery and record-low interest rates have driven British house prices up by about 10 percent over the past year, raising concern some buyers might be taking on too much debt’.  

For recovery to be sustainable it needs to be steady and measured.  Allowing people to borrow money, which they would not have been able to previously afford, to get the housing market moving may have a positive impact in the short term, but could prove to be a recipe for disaster in the future.  There are many high profile examples in the football world of what can happen when money is borrowed to chase a dream, money that is borrowed in the hope that success will produce finances that will more than cover the cost of a loan.  But what happens when you do not get the success you expect? Ask the supporters of clubs such as Portsmouth and Leeds United amongst other, of what they think about this approach, which nearly resulted in their beloved clubs going bankrupt! Borrowing money to those who are likely to struggle to repay their loans when interest rates rise and the help to buy fee commences has all of the same ingredients for disaster.

The real way of addressing the issues within the housing market is to increase supply by building more houses, easy to say you may think!  Simple economics tells us that when there is high demand and limited supply for something, the market will naturally adjust to reflect this, pushing up prices.  Therefore, to deal with the desperate need for housing in the UK and to control house prices, the UK government should be focussing it’s effort on building more houses and not on temporary ‘fixes’ such as the spare room subsidy (referred to a bedroom tax) and schemes such as help to buy!  BBC News Online (Link) recently reported that the number of housing starts had risen by 31% over the last year, however and interestingly, the number of completions only rose by 4% over the year. The article goes onto identify that more needs to be done to increase housing supply in the UK:

‘The housing charity Shelter said the country was still building less than half the homes it needs. "Everyone agrees that we need to build more homes, but sticking plaster solutions like Help to Buy, or tweaks to planning rules will never tackle the hole in our housing market," said Campbell Robb, Shelter's chief executive.

Earlier this week the governor of the Bank of England, Mark Carney, suggested that building more homes was the best way to curb surging house prices.

Above, Shelter’s Campbell Robb refers to help to buy as a ‘sticking plaster solution’. I could not have put it better myself!

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