stopping water run off going under house

[Mart.dawks]

Hi

I was wondering if some one would give me some advice I recently purchased a grade 2 listed house the property is about 300 years old and is timber frame with in filled with brick. Down the side of the house is a tarmac access way which is shared with three other properties. In the structural survey it was mentioned that there was a very high damp reading in the kitchen and Dinning room. The surveyor seemed believe that this could be down to water run off from the access way out side as the floor levels in side and out are about level. From the pictures attached can anyone tell me if there's anything I can do to stop water running under the house as there is definitly a gap between the external wall and pathway also the tarmac looks like its deteriorating.

Thanks

Martin

 

[Me!]

I can't see your pictures to give any specific advice, but one possible solution is to install a french drain. This is basically a trench dug along the edge of the wall, filled with gravel and with a perforated land-drain pipe in the bottom to take away any collected water.

 

[Flyfisher]

I can't see the pictures either so this may not be appropriate but if the Tarmac is deteriorating is there any likelihood of it needing to be replaced? If so, is there any possibility of reducing the level of the pathway, even if this means a step at one or both ends? This would certainly help any ingress of damp onto the house. At the same time, perhaps a 'slot drain' could be installed along the length of the path to totally remove any water from the whole area of the pathway?

 

[Mart.dawks]

Hi

guys thanks for the advice I will try to get some pictures up loaded tonight when I try to do it, it says the files are too big.

I going to look into some sort of drain maybe, the problem I have is the path is shared and one of my neighbours is very territorial when it comes to any work being done.

But from most research I've done it all points to some sort of drain being laid.

cheers

Martin

 

[MatthewC]

I too see no pictures, but apart from the issue of excess water running off and making the walls damp, if the relative heights of the ground outside and the floor inside are about the same, you need to address that. A French drain definitely sounds like the solution if you can't lower the ground level outside. I also hate to think what the water is doing to your timber frame!

Another issue is simply having a solid surface right up to the wall - if rain falls on it, there will always be splashback which will make the wall damp. I was at a mediaeval Grade 1 listed priory the other day, and there was some volunteer laying limestone flags outside on cement, right up to the priory wall! And the charity who own it think their volunteers are wonderful...

Matthew

 

[Bevmarley]

I am no expert but I read an article that said be careful about putting a French drain in as it can affect the foundations and suggested an open drain.

 

[Bevmarley]

See institute of historic building conservation website about French drains and foundations website. Sorry don't know how to attach link.

 

[CliffordPope]

Another issue is simply having a solid surface right up to the wall - if rain falls on it, there will always be splashback which will make the wall damp.

I'd been going to ask this point, but this thread seems a good opportunity as the question arises.
Surely the splashback occurs because the surface is horizontal? Would it therefore be better to have a slightly sloping surface, to throw the water away from the wall? Might this be better even if actually raised the height slightly where the surface met the wall?

 

[Flyfisher]

I think it would have to be a lot more than slightly sloping to prevent splashing onto a wall. More like 45 degrees I'd guess.

Gravel is often suggested for splash prevention but based on my experience I'm not convinced. Here's a photo of our front wall discoloured by splashing water from a dripping gutter (no fixed I might add!). The gutter extends beyond the wall by about 12-15 inches (you can see the dry area against the wall sheltered by the roof overhang) but even so the water droplets still splashed onto the wall, so I wouldn;t underestimate the effect of splashing water.

 

[CliffordPope]

Trying to answer my own question, I've done a google search and basically there seem to be two approaches. One is to lay a strip of something that absorbs or dissipates splashes, such as grass, astroturf, bark chippings, and two is to accept the splashing but to line or treat the wall so that it is impervious to water for the lowest foot or so. Suggestions have included cement render with tanking additive, lead flashing buried beneath the surface render for a height of about a foot emerging as a drip-strip, or for wooden lap boarding an impervious backing for the lowest section of wall.
I'm not sure how any of these sit with traditional methods in a period property.

No one suggests an upward-angled (45 degrees?) edge to the path or tarmac on the theory that, like a mirror, this would reflect flashes outwards instead of towards the wall. But it would be easy to experiment just by leaning a suitable plank on edge against the wall and watching the splashes.

But digging a drainage trench might surely have the converse effect of actually reflecting splashes back against the wall from the outer edge of the trench? In the same way that I've sometimes noticed that a gutter can actually splash water back under the overhanging slates to run down the fascia board.

 

[Mart.dawks]

Thanks for all the advice everyone I'm going to do a little more research and ponder what to do.

I will let you all know how it all goes.

cheers