103L: Housing association pre-purchase damp survey

The RICS homebuyer survey of this former housing association owner flat appeared recommend a damp survey in case a render crack might cause internal dampness.

Surveyor Tips:

  • Render cracks can cause internal dampness, but the cost of repairing them especially at ground level is considerably less than the cost of a damp survey.
  • Render cracks are normally a freeholders responsibility.
  • Here I helped the vendor significantly increase the extraction from the bathroom fan.
  • The property has been dry-lined so the chance of picking up damp from render cracks is low, it also reduces the risk of condensation on the wall, but increases risk around openings.

Root cause

Vapour causing mild condensation around the window openings.


It should be noted that all the external walls looked to be in good decorative order, with no damp staining. 

All the external walls have been dry lined. Dry lining involves separating the wall from the internal surface with small timber batons or insulation, and plasterboard. It’s commonly used as a form of damp-proofing, often but not exclusively, when condensation is an issue.

One of the unintended consequences of dry lining, is cold spots such as around openings.

These cold bridges, or cold spots increase the risk of condensation

The temperature of the windowsill was about 5°C below the ambient temperature of 20°C.

Heat loss increases the risk of condensation.

I detected metal in the window surrounds.

Metal causes rapid heat loss increasing the risk of condensation.

There was dampness near the windowsill, which is less well insulated and close to the outside.

I tested the surface on the inside at the base of all external walls every metre and a sample of internal walls with a Protimeter damp meter in conductance mode. These meters measure electrical conductance of salts in water, a proxy for damp. Readings below 20WME are considered dry. The range is to 8 – 99WME. See surveyor.tips/dampmeter. Walls measured were largely dry on the surface except where mentioned in this report.

The base of walls were dry.

I suspected that there may be condensation in the wall by the rear door but in fact it was dry, which it would not be if water was coming from the ground.

I noticed the Hive thermostat is set to drop to the frost point set at 7°C for much of the day and night.

The hive should be set up so that the temperature never drops below the dewpoint of 10°C on the wall, which is about 15°C at the thermostat, given the 5°C temperature difference.

The extractor fan was dirty inside and had a short over run from when lights are switched off.

The vendor cleaned the extractor fan. This roughly doubled the flow rate. He dropped the humidistat settings so that the fan comes on when it is humid and increased the overrun to about 30 minutes, this will further reduce the risk of condensation.

The two blue controls are in the image above. The left is the humidity setting and the right is the timer setting.

You can remove the cover of the extractor fan easily and adjust the settings as required.

The trickle vents were not open.

Trickle vents are important for insuring background ventilation. They should be kept open to minimise the risk of condensation. The vendor opened the trickle vents during the survey.

The kitchen hob does have an extract ducted extractor fan.

There is a manual  fan, but it did not appear to be sufficient and is probably not used.

Water is finding its way behind a gap in the sealant, behind the kitchen tap.

You should have the sealant repaired.

The vendor’s have a form of washing machine that uses steam.

I suspect but don’t know that this would increase the risk of condensation.

Externally you can see some potential gaps that could allow ingress about 600mm below the ground level.

The gaps are well below ground level and there is no sign of them causing ingress.

There is a small crack just under the master bedroom window.

It is unlikely that this crack would cause internal dampness. As a matter of principle the crack should be filled. You should ask the freeholder to rake it out and fill the gap as part of their annual property maintenance.

There are some small gaps around the double glazed windows.

Again these are unlikely to be causing internal damp but should be filled by the freeholder.

Your lawyers should request that the freeholders disclose all up and coming costs.

Damp issues affecting the fabric of any part of the building could result in apportioned costs under the lease. The roof is perhaps the most expensive repair of any property. It looked to be in reasonable order. However, note I did not look closely at the roof and this is not a roofing survey.

I noted some rainwater spilling over balconies. This did not appear to be causing internal dampness.

I do not know if there are damp issues affecting any other flat in the building, you should make enquiries of the freeholder through your solicitor. 

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