Damp course

[bunser]

Hi,
Our new house was built around 1903, just after we had heavy rain, one corner has damp coming through to the inside wall.
The patch is on 2 walls of the corner, one wall worse than the other and about 28 inches long by 16 inches up the wall, the worst looking bit is about 10 inches up.
Its a cavity wall and wondered why its getting through to the inside. Also how do I tell where the damp course is, on my old house I could see a thin black line but I cant see this on our new one.

Any advice please on what products to use.

Thank you

 

[noseall]

it could be a cavity breach due to mortar snots in the cavity.

to remedy this you may need to remove some of the external bricks in order to remove the material.

making good will depend upon how well you match the mortar and your success at removing the bricks intact.

 

[JerryM]

blocked cavity is quite likely.

also check outside for anything obvious (gutters, paths) - you ideally need to go out when its raining hard to see what's happening. also check for any holes in the mortar particularly in the 1st 3 courses of brick above ground level.

the damp course should be around 150mm above grd level (above the 2nd course of brick). there are a few types ie slate, engineering brick.

products depend on how much you want to get it sorted from stain block (wont stop damp), paint on products to tanking. the finish in terms of the plaster is also relevant. i would do as noseall suggest's 1st or alternatively you could get a couple of quotes from damp proofers to get a feel for costs and then to decide on best way forward.

 

[JerryM]

just a further thought. rain water is either surface (paths, patios, falls ie big hill at back of garden) or from the roof. both should pass into the drain and away.

you need to find the route of the drains around the house and see if they pass the problem area. only way i know to check if you've a cracked drain is to dig out around the area.

only other thought would be to look under the floor boards to check you dont have a high water table.

you need ideally to find the cause before deciding the remedy.

 

[bunser]

The patio does seem to be high, originally the house was brick but at some stage its been rendered and the bottom lip of the render, which curves out slightly, is only about 1/2 inch above the patio. There is a small gap between the patio and house which water could sit.
If the patio is the cause Would I have to lower the patio or is there an easier remedy.

Thanks for your help

 

[JerryM]

iam sure you've found the cause - patio's act to collect a massive amount of water when it rains. patio's must slope away from the house to an area of the garden that can soak up the water.

bottom lip of the render, which curves out slightly

- this is what's called a bellcast. it's a piece of aluminium fixed to the wall before the render is applied. the idea is that is diverts rain hitting the render away from the wall. there needs to be a gap of 150 between the ground and the bellcast. the section of brick below the bellcast is normally painted with bitumen or something similar to stop water ingress.

lowering the patio/correcting the falls is a biggish job although the best technical solution.

thoughts on simpler solutions are:

1) dig out a spade's width next to the wall to a spades depth. paint the wall with bitumen or similar (possibly long strips of DPM with a good overlap may work). backfill with gravel. idea being to produce a soak away

2) dig out along the wall and fit a proprietary drainage system. they are quite expensive though (typ £15/M).

the downside particularly with no2 is that you need to get the ends of the trench to reach an area of the garden where the water can soak away