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News Release from: BRE Bookshop | Subject: Non-traditional housing types
Edited by the Buildingtalk Editorial
Team on 11 March 2005
Identifying non-traditional housing
types
BRE solves problem of identifying non-traditional housing types
In 1986 the Department of the Environment commissioned a comprehensive research programme from BRE, its purpose being to provide aids to identification of the main types of non-traditional housing; information on their construction; advice on their inspection and assessment; and guidance on best practice in their maintenance, repair and improvement Some of this information has already been published, but a significant amount remained unpublished, or relatively inaccessible to potential users
This article was originally published on Buildingtalk on 7 Feb 2005 at 8.00am (UK)
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We look here at a synopsis of the type of information contained on steel framed dwellings.
Steel frames are often disguised About 140,000 steel framed, steel clad (or steel or cast iron-based) system dwellings have been built in the UK and many different kinds of systems have been used.
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Some dwellings date from the interwar period, but the majority date from after the Second World War.
Although there are exceptions, a common feature is that the finished building was made to resemble a conventionally built dwelling, with preferred finishes of brick, imitation brick, or render.
Some of the disguises are nearly perfect and it takes more than a superficial examination to discover that some dwellings are indeed steel framed.
Possibly the easiest way to establish whether a particular dwelling is steel framed is to inspect the roof space, as most steel systems had steel roof trusses, exceptions being the Dennis Wild system which had timber trusses with steel tie rods and the Thorncliffe system, which had a conventional timber roof.
Vulnerable parts of the structure Failure of the original protective coatings of the steelwork typically occurs where rain can penetrate the external skin, allowing water to be held in contact with the steel by masonry or rendering, or be trapped in the cavities.
Identifying places where there may be rain penetration is critical - for example these can be projecting ledges or springing cover moulds over joints, jointing material or pointing coming loose and holes for fixing ventilators.
Column bases fixed directly on the concrete, but not covered, should be inspected.
If the original protective coating is no longer intact, the steel will be corroding and the column base should be exposed for a physical check.
Steel framed houses are more sensitive than traditional construction to lack of weep holes, blocked weep holes near to ground level, or rubbish in the cavities.
Assessment of remaining life Without repair A distinction must be drawn between steel frames that consist of hot rolled solid sections and the much lighter members in fabricated, cold rolled or folded sheet steel.
In the latter case there is simply less steel, with obvious effects on the length of life once the protection is removed.
The age of the dwelling in itself is not a sure guide to the corrosion that can be anticipated and is insufficient grounds on which to condemn a dwelling.
Corrosion appears to progress at varying rates, depending on the system characteristics and the weather tightness of the dwelling.
With repair Where the protective coating has deteriorated, but significant corrosion of the steel has not yet begun, a decision has to be made regarding the amount of stripping out necessary to allow access to the coatings, which need attention.
Where the opportunity is afforded by the removal of, say, external leaves, then the renewal of protective coatings is clearly to be preferred to the patch repair of coatings.
Dwellings, which on inspection show an appreciable amount of corrosion in some of their steel members, will pose a problem.
Those affected are likely to need their corroding steel members cutting out and replaced by welding in replacement steel.
Given adequate cleaning and application of a suitable protective coating, there is no reason to suppose that the life of such steelwork will be any less than the 30 years before any further attention is needed and it may be considerably more.
Highly fabricated sheet steel members which are of too light a section to withstand conventional arc welding are another matter.
Once the protection has gone, corrosion does not take long to perforate the sections and repair of these may be more difficult to effect economically.
Entitled Non-traditional houses: Identifying non-traditional houses in the UK 1918-75, the new book is complete with photographs, cutaway isometric drawings and many aids to identification.
There is comprehensive information on construction and possible faults, plus general advice on inspection and assessment.
It is accompanied by a CD-ROM that has a search tool to enable house types to be identified using information gathered during investigations.
For more information on this invaluable book, contact BRE Bookshop.
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