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  • Houses of Non-Traditional Construction

    19th March 2018

    Houses of Non-Traditional Construction

    What determines if a house is traditionally constructed or non-traditionally constructed?

    Simply put traditionally constructed homes are built from stone / bricks and mortar. Non-traditional methods are properties built with concrete or steel frames with small or large panel walls. There are a number of examples which we will look at below.

     

    But first, why does this matter?

    The main reason is the concern for buyers and mortgage lenders as some non-traditionally constructed homes suffer defects that are not commonly found in the general housing stock (properties of traditional construction) and can require expensive repairs. For mortgage lenders this can result in having a property which drops in value and is not a suitable collateral for their loan. For the buyer this can mean bearing unexpected repair costs and being unable to sell your home. While a cash buyer may not be affected by the fact some mortgage lenders will not lend against certain non-traditional homes it does limit the number of buyers you can sell to later on.

     

    Why were different construction methods introduced? 

    After the Second World War there was a large demand for new housing. This was met by prefabrication which offered various types of industrialised building systems and with that increased efficiency and speed on site. Properties built using these new processes were know as system-built properties. The earliest system-builds date back to the inter-war period, however, it was between 1945-1955 in the post-war period where 20% of new housing was via system-builds. A further 750,000 homes were construct between 1955 and 1970.

    Around 1970 many of these new systems were found to be unsatisfactory and liable to unacceptable levels of deterioration or even failure. Some of these issues are thermal and noise insulation, condensation and even structural failure. The government introduced legislation under the Housing Defects Act 1984, which allowed local authorities to designate particular types of property as ‘defective by reason of their design or construction’, and fund remedial work. In total, 26 specific systems were designated defective. Not all examples are structurally defective, but it is the inclusion on this list that causes mortgage lenders to be cautious.

    The following property types are listed:

    Airey, Boot, Cornish Unit, Dorran, Dyke, Gregory, Hamish Cross, Myton, Newland, Orlit, Parkinson Frame, Reema Hollow panel, Schindler and Hawksley SGS, Stent, Stonecrete, Stour,Tarran, Underdown, Unity and Butterley, Waller, Wates, Wessex, Winget, Woolaway

     

    What types of non-traditional construction are there?

    There are a number of different systems developed over the years (each with their own potential defects) that generally fall into categories of steel framed, timber framed, precast reinforced concrete construction (PRC), and cast in-situ concrete construction.

     

    Examples of Non-Traditionally Constructed Houses

    Schindler House

    Houses of this type were constructed from pre-cast concrete panels which were factory made and then put together on site. They were a lot quicker to construct than brick built houses but they were intended to have a life span of about 30 years. It can be hard to tell a Schindler house apart from a traditionally constructed house. Whilst there is a frame it is well hidden behind brick external walls and a traditional roof. Even within the roof space the house can appear to be of traditional brick construction. What can make it even more difficult to tell these houses apart is that they can be built on estates where they are surrounded by traditionally constructed homes. There is a risk that you could unwittingly purchase such a property only for the next buyer to realise it is un-mortgageable leaving you stuck with the property.

    Repairs on these properties can be carried out from either the inside or outside meaning it can be hard to tell if any repairs have taken place as the original walls can remain in situ. If you enter a local authority estate where some of the properties have rebuilt walls this can be indicative of this house type being present.

    Like a number of non-traditional construction methods, this type of property was designated defective and cannot be mortgaged.

     

    No Fines Construction

    The most common type of no-fines concrete construction is the Wimpey No-Fines, like others,  named after the developer who created them. These properties are built by pouring concrete into a timber frame. Once the concrete as set the timber is removed leaving solid cast walls. The name no-fines comes due to the use of a special aggregate made up of round pebbles and no fine particles (hence the name no-fines).

     

    no-fines-concrete-external-gable
    Source: KDLT Building Services
    wimpey no fines house
    Source: bisfhouse.com

     

    The benefit of this construction type is that it resisted penetration damp. Rain water dripped off the pebbles preventing it from passing through to the interior due to the absence of finer particles.

    There are some features that can help identify this type of property – from the outside they look like standard post-war semi-detached houses with rendered walls. Often, but not standard, is a matching rendered concrete chimney stack. However, the simplest way to identify this construction type is by looking at the inner face of the gable end in the roof space where you can see the round pebbles in the wall.

    More often that not the Wimpey no-fines is accepted for mortgage purposes. However, this isn’t the case for all no-fines types due to specific known defects with some other versions.

     

    Cornish House

    This house type is typically constructed using concrete panels on the ground floor level with a timber frame covered with tiles on the first floor and roof. Other versions have ground to roof level concrete panels. This house type is designated defective and not mortgageable unless it has been repaired via an approved scheme.

    These houses fair when water enters the concrete panels and the steel reinforcing rods corrode. The corroding rods expand causing the concrete to spall or split open. Some houses were retrofitted and faced with insulation to try and solve the problem, however, in most cases the problem still exists. Often the only real solution is complete removal of the walls to rebuild.

    Cornish House
    Source: the-mortgage.co.uk

     

    Airey Construction

    Another property type that is un-mortgageable and is now quite rare. It was a common property in small cul-de-sacs in village locations. They are built using reinforced concrete columns with external concrete panels. The inside is dry lined with plasterboard. A common feature of many types of non-traditional construction, including this one, is tile cladding to the top of the gable end.

    What went wrong with this construction type? The concrete columns were too thin and allowed moisture to penetrate through to the reinforcing rods causing them to corrode and weaken the structure. These properties are not mortgageable on any terms. In order to make this property type mortgageable the concrete components must usually be removed and replaced with modern cavity brick walls.

    Airey House
    Source: the-mortgage.co.uk

     

    Cussins House

    This is a metal framed house and not particularly common. Like the Schindler house they can appear to be of traditional brick construction. However, the brick walls are stacked rather than laid in the conventional manner which gives rise to vertical and horizontal joints. There are no actual bricks, rather concrete panels with brick effect bolted onto the metal frame.

    Often an intrusive structural report is required as a condition of getting a mortgage as the metal frame extends down to ground level where there is a high risk of corrosion. The fixings between the panels and frame are a point of weakness and can also suffer failure.

     

    BISF House

    The first thing to recognise when inspecting a house is whether or not it is of traditional or non-traditional construction. A traditionally built house may be described as one constructed from bricks and mortar. An example of a non-traditional house is one built from a concrete or steel frame with small or large panel walls. There are many, many different types. Spotting one is obvious in most cases, but not always.

    The photo below is of a BISF house. BISF stands for British Iron and Steel Federation. They were built in the early post war years when there was a shortage of traditional building materials. They have concrete walls at ground floor level and a metal frame above with metal panels bolted on. The roof structure is also a metal frame and is covered with metal sheets (or sometimes asbestos cement panels in the early days).

    Obtaining a mortgage on one can be difficult and they used to be subject to limited lending criteria. Perhaps someone could update me on that. Consequently relatively few found themselves into private hands. Market values are usually always less than a comparable traditionally built house. From an investment point of view, you may get a good return, if you can get a mortgage on one.

    BISF house
    Source: geograph.org.uk

     

    Overall

    As with any property purchase it is useful to get a survey to make sure you don’t miss anything important. Not all houses are built the same and each construction type has its own typical repair issues to consider. Assuming a house must be fairly standard because it appears to be can be a costly mistake.

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