MY DREAM HOME’S A PRE-FAB

Q My partner is interested in buying an Airey house which has been
listed as a defective dwelling. What are the likely problems we may
encounter, and the rough costs that we could expect to incur?

JR, Suffolk

A The Airey house is one of a number of factory-built, or “prefab”
houses that were built in large numbers following the Second World War. Some
25,000 Airey houses were built between 1945 and 1955, and are characterised
by horizontal rows of precast concrete panels – often looking shabby these
days.

Like the Trusteel houses I wrote about earlier this year, Airey houses have a
limited life, which is coming to an end. This wouldn’t be such a disaster if
the houses were still in local authority ownership, as they could be
demolished and replaced, and the tenants rehoused. But unfortunately some
council tenants took advantage of the “Right-to-Buy” scheme to purchase
their Airey houses at a discount, so they are stuck with a property that has
been ruled defective by the Building Research Establishment (BRE).

The main problems are due to a high chloride content in the precast reinforced
concrete panels and structural columns, which has led to cracking damage and
water penetration. There is nothing that can be done to repair these
defects, and the only option would be to demolish the house and build a new
one on the plot. Except that Airey houses were generally built as pairs of
semis, so there may be a problem with supporting the neighbouring house,
which might still be in local authority ownership.

I have to advise you not to buy this house, unless you can get it for the
price of the land only. The Airey house should be held up as an example
every time a politician claims that factory-built homes are “the future
of housing”.

STAIN REMOVER

Q We recently left a bag of gritting salt in our entrance porch. It
must have leaked because we now have a dark “damp” stain on the quarry-tiled
floor. I have washed the area down several times, even using a carpet
cleaner that sucks up dirty water. Can you suggest anything that may help?

LS, by email

A What you are describing is the hygroscopic (“water-loving”) nature of
salt. This can best be observed in a steamy builders’ “greasy spoon” café on
a cold winter’s day. The salt cellar on the table will be hard to pour, and
you might see droplets of water forming around the top, where grains of salt
have absorbed water from the humid atmosphere and dissolved.

Hygroscopicity causes some common dampness problems in buildings, which can be
baffling for householders, and also for the surveyors and jobbing builders
asked to investigate.

For example, “chimney damp” causes staining on chimney breasts in older
houses, even when there are no rainwater leaks down the flues. The salts
deposited in the brickwork from years of burning coal or wood are
hygroscopic, and absorb water from the atmosphere.

Similarly, I get regular letters from people whose homes have been converted
from barns and other former agricultural buildings, who are puzzled by
persistent damp patches — often despite chemical “damp-proofing”.

The culprit in this situation is usually animal urine, which has soaked into
floors and walls, and has the same hygroscopic effect.

The good news is that hygroscopic salts can always be removed, because they
are water-soluble. It is simply a process of repeatedly flooding the
affected area with clean water, and sucking up the salty water with a
“wet-vac” vacuum cleaner, such as the carpet cleaner you already have.

Send your questions to Jeff at Life, The Sunday Telegraph, 111
Buckingham Palace Road, London SW1W 0DT, email askjeff@telegraph.co.uk

Also visit askjeff.co.uk