Non-Traditional Housing Stock - Strategic Planning

Guest article from Joe Malone BSc(Hons) ICIOB Head of Asset Management ALMO Business Centre Leeds

The average SAP rating for non-traditional stock is around 45 yet social housing providers should be aiming for a target SAP rating of 80

Figure 1: A Typical Pair of Airey Non-Traditional  PRC Houses

To date I have written two survey strategies to give housing providers guidance on dealing with their non-traditional housing stock. The scope of recommended survey and the information gleaned is critical to planning any investment or indeed, disinvestment, into non-traditional stock. Contrary to popular belief specialist structural survey work is not always required and even where a structural engineer is required it is important to define the scope of inspection to ensure the information is focussed and relevant.  The survey strategy should  be balanced against the view that the aim of the asset management strategy is to secure a 30-40 year lifespan.  When we talk about this lifespan we are not simply talking about these buildings being structurally sound for another 30-40 years; we have to recognise that these buildings in ‘as built’ condition are technically obsolete, particularly with regard to thermal efficiency. The average SAP rating for non-traditional stock is around 45 yet social housing providers should be aiming for a target SAP rating of 80, admittedly a challenging target when you consider that the average energy efficiency SAP rating of new homes was 79.4 in England for the quarter January – March 2012.

What is a Non-Traditional House?

In essence it is any property that is not built using traditional methods and materials. A traditionally built property would be of solid wall or cavity wall construction built with masonry (bricks/stone/blocks) and mortar (OPC or lime). Arguably even todays MMC (Modern methods of construction) will in future be defined as non-traditional stock because it uses non-traditional fast track on site or off site construction techniques. We can only wonder as to whether in future these methods become so commonplace that they become the norm and therefore traditional, but I digress…

The scope of this article is to discuss the non-traditional stock that sprang up after the war in response to the national housing shortage and the shortage of traditional build materials and shortage of a skilled workforce to build at the required demand. The answer was found in system build housing, particularly Pre-reinforced concrete (PRC) and In-situ (poured on site) concrete systems. Additional there were a number of steel/timber frame and hybrid systems clad with a variety of materials. It is this huge variation in non-traditional stock that can make property identification extremely difficult for the average building surveyor. 

The problem with Non-Traditional housing

Figure 2: Corroded reinforcement due to low concrete cover on 

a Reema hollow panel system

We’ve touched on the poor thermal comfort in these properties and along with this many properties are prone to damp, particularly condensation damp due to cold bridging but also penetrating damp due to failed building joints. In general most non-traditional housing systems have performed well from a structural point of view, although some problems developed with a number of system-built dwellings. By the 1980s some fundamental problems affecting structural stability and durability began to emerge in some of the concrete system built houses. The problems occurred because of either carbonation or the presence of chlorides in the concrete and resulted in the corrosion of steel reinforcement and subsequent cracking and spalling of the concrete. The issue of carbonation was exacerbated in many of these systems by the slenderness of many of the components involved which offered comparatively little cover to the steel. Steel reinforcement should be covered with at least 65mm of concrete to afford the required degree of resistance to corrosion.

The problems of carbonation and the presence of detrimental chloride levels in reinforced concrete dwellings led to certain concrete housing systems being designated defective under the 1984 Housing Defects Legislation which was then incorporated into the Housing Act of 1985. A company named PRC Homes Ltd (a subsidiary of NHBC) was set up to licence repair schemes for housing systems designated as defective under the Act. The extent of works and costs involved in some of these repairs was very substantial. No steel or timber systems were ever designated as defective. The PRC Homes Ltd scheme was discontinued in 1996 and most of the original 10 year warranties on properties gained from this scheme will have now expired.

A lot of our non-traditional stock was never designated as defective and therefore never repaired under an approved repair scheme. The following table gives you some understanding with regard to how mortgage companies view these properties:

A	Acceptable for normal terms - e.g., some post-1960 timber and steel frame    houses, some in-situ concrete and concrete block systems.
B	Unacceptable - But special cases of high merit can be considered. These will be generally high value properties with proven demand. Properties that are accepted locally by other major high street lenders may also be considered, even if values are lower than traditionally built properties; however, there must be a proven demand for the properties.
C	Unacceptable in original condition but suitable for normal terms on completion of acceptable repair scheme. Any repair scheme must include the whole structure/block, please refer details to Risk Policy, NAC, (for PRC properties designated as defective under the 1984 Housing Defects Act, see terms F).
D	Acceptable up to 85% loan to value in original condition and normal terms on completion of acceptable repair scheme, e.g., BISF houses and other Steel systems.
E	Acceptable for houses and bungalows not more than two storey’s in height, provided that a survey and appraisal from a Structural Engineer is available in accordance with the BRE Guidance Appraisal - Part 2 of study of LPS
F	PRC properties designated as being defective under the 1984 Housing Defects Act. Unacceptable in original condition. Acceptable on completion of an approved repair scheme to whole structure/block. Limited terms may be applied.

Essentially each non-traditional property is assigned a category A-F which affects the mortgageability of that property and this is important because it gives us an idea of which types were repaired under approved repair schemes and which were not. It also gives some guidance as to which properties are subject to a structural engineer’s appraisal.

BRE Guidance

You may have noted the reference to the Building Research Establishment (BRE) contained within the table above and this is because they have been incredibly active in researching defects in non-traditional stock since the 1980’s and have built up a bank of core reference material, which is available on CD Rom and titled: Non-traditional housing:constructional details, assessments of condition, maintenance and repair.

Critically this reference material contains clear guidance on the level and detail required for surveying non-traditional stock to determine its structural adequacy and can be used in conjunction with a range of other desk top reference material to structure some survey guidance for individual archetypes. For example guidance for  ‘Cornish’ units might look like this…

Cornish Units

These are PRC properties subject to mortgage category F which means they were designated as defective under the 1984 Housing Defects Act. All properties should have undergone repair under an approved repair scheme and can be considered exempt from the structural problems affecting untreated Cornish properties if that proves to be the case. Untreated properties have a standard SAP rating of 51.8 and once potential structural problems have been assessed and remedied then refurbishment works should focus on improving the thermal efficiency of these properties. Condensation damp was a notoriously frequent occurrence in untreated Cornish properties and improving thermal efficiency will go some way to addressing any issues relating to condensation damp.

For untreated Cornish properties the following overall survey procedure should be adopted:

The site investigation consists of three stages:

1. The visual inspection of inside and outside of dwellings. 

2. The visual inspection of structural components where normally exposed on the inside and outside.

3. Examination of components by uncovering reinforcement for visual inspection and measurement of cover, by taking samples of concrete for analysis to determine chloride and cement contents and to assess the depth of carbonation and the depth of cover to rebar.

Figure 3: Cracked column in 'Unity' due to high Chloride levels

The completed survey strategy details an approach for every property archetype whether it be low, medium or high rise. We have over 400 high rise blocks in Leeds the majority of which are cast in-situ or PRC blocks and we have a strong focus on both structural integrity and fire safety in these blocks. Build archetype also determines fire compartmentation and means of escape so these issues are inevitably discussed in the final analysis.

Even where properties were subject to approved repair schemes in the 1980’s & 90’s many of these properties still suffer poor thermal efficiency and generally across all non-traditional stock, residents experience cold and damp conditions and subsequently high fuel bills. Many landlords have targeted their non-traditional stock for external wall insulation (EWI), though this is partially because some of these properties qualified for funding under the Governments Community Energy Saving Programme (CESP). You must consider the structural issues in conjunction with the cost and efficacy of upgrading properties to modern standards of thermal comfort. Whether or not external wall insulation is the best way forward in securing another 30-40 year lifespan on non-traditional stock will be the subject of the second part of this blog.

Joe Malone BSc (Hons) ICIOB Head of Asset Management ABCL

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