Damp wall and rotten joists

graeme16

No update to note as of yet on the damp issues as I have been concentrating on other aspects of the house. I am going to start a generic post of the house to assist with other aspects but will keep this thread active for the damp issues.

boldaslove

FreeBear said:

If (when) these damp "specialists" return, do not be suckered in to spending money on injected chemical DPCs or the waterproof render/plaster treatments they usually recommend - Neither are effective long term cures (they just mask the problem for a few years). And if they recommend the schrijver system, give the guy a kick up the backside as he leaves.

Can I ask why this is and what the alternative solution is? We’re currently renovating a 1930’s house and have discovered severe woodworm infestation in the floor/joists downstairs caused by lack of underfloor ventilation. At least one contractor has advised hacking off 1.2m high plaster downstairs and replacing it with a damp proof membrane/plaster (alongside replacing the wooden floors downstairs). I can’t see any visible damp issues in the internal walls apart from a small section of the hallway which looks like it might’ve been causing by a leaky pipe so it seems a bit extreme to suggest pulling plaster off everywhere!

stuart45

Improving the ventilation and fixing the new joists with joist hangers would be a good start.

troffasky

boldaslove said:

At least one contractor has advised hacking off 1.2m high plaster downstairs and replacing it with a damp proof membrane/plaster

This is definitely not "normal". This sounds like a measure to mitigate damp in the wall that is otherwise incurable, rather than the first choice when trying to fix damp issues on an internal wall.

FreeBear

boldaslove said: At least one contractor has advised hacking off 1.2m high plaster downstairs and replacing it with a damp proof membrane/plaster (alongside replacing the wooden floors downstairs). I can’t see any visible damp issues in the internal walls apart from a small section of the hallway which looks like it might’ve been causing by a leaky pipe so it seems a bit extreme to suggest pulling plaster off everywhere!

A nice little earner for this contractor, and he will be long gone by the time you discover that the work didn't actually cure the problem. There should be an air brick every 2-2.5m along the outside walls and the ground levels clear of the air bricks - Ideally, 150mm below the DPC, but with 1930s era builds, that would expose the footings, so 75mm should be the minimum. A shallow trench 200-300mm wide filled with a decorative gravel will reduce the chance of rain splashing the wall above DPC level.

If your joists are in contact with the external walls, dipping the ends in a wood preservative will reduce the chance of new ones rotting - For a while, building codes used to suggest dipping in bitumen.

boldaslove

FreeBear said:

boldaslove said: At least one contractor has advised hacking off 1.2m high plaster downstairs and replacing it with a damp proof membrane/plaster (alongside replacing the wooden floors downstairs). I can’t see any visible damp issues in the internal walls apart from a small section of the hallway which looks like it might’ve been causing by a leaky pipe so it seems a bit extreme to suggest pulling plaster off everywhere!

A nice little earner for this contractor, and he will be long gone by the time you discover that the work didn't actually cure the problem. There should be an air brick every 2-2.5m along the outside walls and the ground levels clear of the air bricks - Ideally, 150mm below the DPC, but with 1930s era builds, that would expose the footings, so 75mm should be the minimum. A shallow trench 200-300mm wide filled with a decorative gravel will reduce the chance of rain splashing the wall above DPC level.

If your joists are in contact with the external walls, dipping the ends in a wood preservative will reduce the chance of new ones rotting - For a while, building codes used to suggest dipping in bitumen.

Thanks for this - it was suggested in addition to replacing the joists/floor and adding more air bricks but I did think it sounded a bit extreme!