So much for rising damp, so much for woodworm !

By George Hockey

So much for rising damp!

Upon completing a remedial basement waterproofing contract in Highgate where liquid applied bitumen tanking had seriously failed (case study will be forthcoming on our web site), a neighbour requested a survey for basement conversion in her 1930’s property.

In discussing the project after inspection, the lady householder asked whether we undertook damp proofing and woodworm treatment, this because I mentioned that some evidence of woodworm was seen in a lintel within the basement, but that it showed no sign of recent activity.

The householder advised that they had not been in the property very long and that a major preservation and damp proofing company had inspected and were about to undertake woodworm treatment at ground floor, and that three areas of damp proofing had been quoted but not yet put on order.

With the house having a semi-basement, i.e. only a metre or so within the ground, the ground floor sat high above ground level, so rising damp would need to travel a good height to cause problems above at ground floor. In view of this I asked her to show me the areas of proposed damp proofing.

One was within an opened up fireplace/chimney breast now used as a recess in which a kitchen unit is located. I tested the moisture profile with a conductance meter and advised that the high surface readings were more likely to be as a result of plaster contaminated by residual flue salts, i.e. hygroscopic dampness, and that new plaster with a salt retardant rather than injection damp proofing and plastering was the true answer.

The second area was below a stone window cill that was clearly worn, collecting water on the upper surface at one end, below which the local mortar beds had washed out to cause water to penetrate internally exactly where ‘rising dampness’ was to be dealt with.

The third was local to a poorly tied external added brick pier that supports framework for a garden gate, with rain-water splashing back at the top of the wall and also penetrating down at the interface between the pier and house proper.

In all three cases a remedial damp proof course had been advised, all a waste of time because while all would benefit from repair of damaged plaster, along with inclusion of additives, the cill and pier problems require repair (of the cause), otherwise the same dampness would eventually occur again.

The Property Care Association (PCA) Code of Practice, which we work to, clearly states that one should prove what it is not, before stating what it is, where surveying for rising dampness is concerned. Sadly in this case the code was not followed.

And so much for Woodworm!

The same company proposed, and an order had been placed, to lift floorboards and spray the unpainted ground floor flooring timber for a sum of approximately £350.00.

Unless I did not see everything presented by the company to the householder, which I believe I did because the papers were in bound folders, it was all the paperwork associated to both the damp proofing and woodworm treatment but was very short and gave little detail.

The householder has a baby and was concerned about the use of chemicals, so I explained to her that without undertaking extensive preparation works in respect of vacuuming voids etc., it would be unsafe to just lift periodical boards and spray because the accumulated dust as well as the timber would be treated.

On the basis that if the infestation was later proven as active and widespread, with treatment justified, I would calculate that such a job would a good £2,000 rather than £350.00 because of the need to open up and clean out the voids, and knowing that some of the basement ceilings are extremely degraded, with much plaster having fallen off the laths, I knew that the proposals included no cleaning, so were poor and dangerous.

In conclusion I advised the lady that the basement ceilings would all need to be removed anyway during the basement conversion when better consideration of necessary woodworm treatment scope, if any, could be given, saving much on cleaning out voids, again emphasizing that in my opinion the advice and proposals she had to date were unproven and wholly unsafe.

Read about George's background in building preservation here:

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