Client waited 4 months for a peace of mind survey during the Covid lockdown winter of 2020/21. The end of terrace house had been extended. A ground-floor shower was leaking (repaired before the survey) causing water to be absorbed through to the extended porch and recycle by condensation onto the cold external porch wall.
Surveyor Tips:
- Peace of mind surveys are some of the most interesting and most appreciated.
- Here I showed the client a simple technique for testing for a leak from the mains water that every survey should consider using.
- The explanation was complex and detailed but appreciated by the client.
Root cause
Shower leak fixed before survey, condensation.
Illustrations
The salt is calcium sulphate, a key ingredient in cement and mortar. If diluted in water salts tend to move to surfaces. These can be removed with sandpaper and decorated. There is also a brown, teabag stain like discolouration, a sign water has passed through brickwork.
This low level of damp indicates that the wall is drying out on the internal side of the porch.
On the external side of the wall water appeared on the wall in a symmetrical rectangular fashion. There were dribble marks. This is a sign of condensation on the cold sections of wall. If there was penetrating damp, that is rainwater from the outside, there would probably be a brown stain. Vapour from the internal wall is condensing on the coldest part of the porch.
The porch appears to have been constructed of large breeze blocks. The mortar loses temperature rapidly, compare to the blocks.
It was clearly very damp some months ago.
Walls dry from the surface inwards towards the centre, at a rate of about 1mm per month.
Radio waves at a set frequency can identify damp deep within a wall. They cannot differentiate between water and other dense matter. I found damp up to about 1.3M. There is much debate about how to dry a wall fast. From a practical perspective, if water is free to evaporate from the porch wall, I think you can re-tile the bathroom before the centre is dry.
The rot was probably Coniophora puteana, or cellar rot, a brown wet fungus, and wood weevil, see surveyor.tips/rot. Rot requires water to grow. Wood weevil requires rot. Remove the water and both will stop damaging timber. The floor has been replaced with a solid floor so there is no realistic risk of rot continuing to grow.
Your builder should rake out and fill cracks (an external acrylic caulk for small gaps and similar material to the original render for larger gaps >1-2mm). The remove flaking paint and repaint with a suitable masonry paint
Consider increasing the triangular skirting at the base of the wall with a cement mortar.
This dribble marks are a sign of condensation from insufficient ventilation and to lesser degree insufficient heat or poor insulation.
And I don’t believe that the cracks are causing penetrating damp but they should be filled. The wall will act as a thermal thin increasing heat loss and therefore risk of condensation.
The problem with the extractor fan is it switches off once lights are turned off. I recommend replacing it with a continuous flow extract fan see recommendations.
Other matters
It could be a challenge installing the fan in the kitchen so consider other methods of minimising production of vapour, see recommendations
It is worth using this neat trick to regularly test for a mains water leak, see https://surveyor.tips/leak-tracing/
Consider installing a bathroom extractor fan, see other practical recommendations.
This is not a roofing report. I believe the most likely cause of dampness in the loft is this flashing. If the flashing is lead, it can probably be remoulded back into place by a competent roofer. However if they are going to charge you for scaffolding, then it would be worth replacing the lead and putting up a cowl (top to chimney pot), and ask them to check other aspects of the roof at the same time.