Property Maintenance in Merstham (RH1)
Damp that starts a couple of brick courses above the outside ground has nothing to do with the roof. Paths, patios and borders creep upwards over the decades, and once the ground outside an older Merstham house sits higher than the damp course, the wall has no defence left.
How ground levels cause damp
A Victorian or Edwardian house has a damp-proof course a couple of brick courses above the outside ground level, and everything below that line is expected to be wet.
When a path is relaid over the old one, a patio is added or a border is built up against the wall, the line gets buried and the moisture in the ground simply carries on upwards past it. Indoors that shows as a tide mark on the lower part of the wall, salts in the plaster and skirtings that never dry out. The repair is largely outside and largely groundwork: cut the levels back down below the damp course, form a drained channel where the ground cannot be lowered, and make sure the finished surface falls away from the house rather than towards it. Doing that and then letting the plaster dry is far more effective than treating the plaster first. Levels, drainage, brickwork and plaster are all our own team's trades; roofing, electrics and heating are specialist work we bring in and manage.
Gullies, air bricks and the things that get covered over
Two more things get buried in the same way. Gullies at the foot of downpipes silt up or get paved over, so a whole roof's worth of water discharges against the wall instead of into a drain. Air bricks ventilating a suspended timber floor get blocked by soil, render, paving or a garden bed, and once the underfloor space stops breathing the timbers stay damp and the floor begins to go. Both are cheap to put right and both cause disproportionate damage when they are not. On the post-war housing east of the village the same principles apply with different details, and on the older terraces and the listed cottages in the conservation lanes the work carries the added requirement of not changing how the building looks or how its walls behave.
Then, and only then, the making good
Once the outside is right, the inside can be repaired properly: hacking off failed plaster, letting the wall dry, and replastering in a system that suits a solid wall rather than sealing it.
Doing it the other way round is why the same wall gets done three times in a decade. We would rather do the outside first and the plaster last, and we will say so at the survey even where it is not what you were hoping to hear.
More in Merstham
Everything we do in Merstham is on the Merstham area sheet, and the full detail of how we approach this trade is on the building maintenance page.
Common questions
Q.01Why is there a tide mark on my downstairs wall?
Usually because the ground outside has risen above the damp course, or a gully or downpipe is discharging against the wall. Both are outside jobs, and both are cheaper than repeatedly replastering inside.
Q.02Can the path be lowered, or does it have to come out completely?
It depends how much it has been built up and what is underneath. Where levels cannot be dropped far enough, a drained channel along the wall does the same job. We survey it and price whichever is right for the house.
Q.03My floorboards feel springy near the wall. Is that connected?
It can be. Blocked air bricks stop a suspended timber floor drying out, and the joist ends nearest the wall go first. It is worth checking the ventilation before anyone lifts the floor.
Q.04Do you work on the listed cottages in the conservation lanes?
Yes, with the consent position established first and the repairs kept like for like. Old walls need breathable materials, so we would not put a sealed system on one.
Thinking about building maintenance in Merstham?
Tell us what you are planning. We come out, look at the job properly and give you a price for it.