Drive Drainage

[busdriverman]

Hi folks new to the forum, any advice gladly accepted! I have just set about renovating / repairing a house I have just moved into. The front of the house and part of the side of the house had / has a damp problem.

I have identified the source of the damp as a combination of the ground being too high - it was two courses above the damp proof course at the front of the house . I have dug this out and the masonry seems to be drying out nicely. I will now pave it and install some drainage.

The problem looks to be the same along the side of the house, the ground is too high – almost level with the damp proof course due to the brick drive being too high (previous owner). Also there is a poorly installed gutter downpipe.

The problem is the drive is fairly long (and narrow so next to useless!) but is a reasonable brick finish. I am loathed to dig this up to try and lower the level of the drive as plenty of other work needs doing / paying for - but if it’s the only solution?

Can drainage sort this problem?
1) Can I install a French drain down the side of the property
2) Can I install linear drain channel down the side of the property

My concerns with a French drain are that it will have to be butted up right against the wall of the house and will be going in near the foundations - this doesn’t sound like a good idea to me?

My concern s with linear drain channel are that it will only drain surface water - will the area under the channel / drive still seep water into the side wall of the house.

Any input much appreciated!

Matt

Photos with descriptions should be on here
//www.diynot.com/network/busdriverman/albums/

 

[Blagard]

From the photo's it would seem as if your house has a couple of courses of blue bricks, possibly as the DPC. If you expose the "red" bricks below the blues there is a risk they may perish due to exposure to frost. - It depends entirely on the brick of course, checking out the neighbours houses may give you a clue if they built at the same time.

Can you please advise based upon your observations what the DPC actually is and where it is located relative to the blue bricks if it is a dedicated strip of DPC.

 

[busdriverman]

Hi thanks for the reply, the bricks that look blue are in fact red bricks but they have been painted with bitumen paint. This was also done on the front of the house, I presume when the damp problem manifested itself inside the house as mould on the plaster. The Bitumen is pretty roughly put on. The house is 1930s build , cavity wall , and the damp proof course is two layers of slate in each skin.
Thanks again

 

[Hugh Jaleak]

The downpipes could also be part of the problem. Not sure where the left one goes to but the right hand pipe with the shoe fitted could have been splashing back onto the brickwork, hence the mortae was put on to try and alleviate that. I'd be looking to reroute these pipes so they discharge cleanly into the gulley, without splashing back up the wall.

If problem still manifests then time to rethink, but drainage in a poor condition can often be a contributory factor to damp issues.

 

[Blagard]

A slate DPC should do an excellent job. It is also very clear where your DPC actually is.

The cavity wall construction basically means the inner leaf should be dry in any event. The only reason for it to fail would be water in the cavity above DPC (resolved by lowering the ground and introducing some weep holes) or debris in the cavity bridging the DPC. Most likey you may have some of the latter though hopefully not enough to be a problem.

French drains in my opinion are better suited where they are part of the original design. They can clog up but are certainly better than nothing. You are right about the channel drain and unless it is installed below DPC it really is unlikely to help at all.

Your first course of action is ideal - Reduce the level outside below the DPC. Doing similar down the side of the house would happen anyway as soon as you excavate for a channel or french drain. Consider if you can, leaving a margin low, filled with free draining aggregate (top below DPC) and top off with a grating if it risks getting a foot trapped. Naturally such a margin will have an open end to already lower ground. This is neither a true french drain or channel but will keep your ground level where you want it to be. It is not suitable if the paving falls towards your house as then you would also need a channel drain in front of it.

In any event do consider a channel drain for any condition when paving falls towards the house walls. - That is unless you can change the falls away from your house which would be even better.

I concur with Hugh's comments on the downpipes

 

[busdriverman]

Blaggard and Hugh many thanks for this input .

The cavity is in fact bridged with sand etc and I will need to clear it . I will also reroute the downpipes as suggested.

I think I am getting a clearer picture now on the drainage side of things. If I dig out the side of the house to below the damp proof course by say 8 inches and then install linear channel at this level - would this be the best solution? It will leave me the problem of what to put on top of the channel to stop people putting their foot down the gap - but maybe some "stand alone " grates are available?

Is there a recommended distance for installing channel from a wall - or is having it directly next to the wall acceptable?

Keen to do everything I can to solve this.
Thanks again
Matt

 

[Blagard]

You need to think about what a channel will be draining. Do you really need the channel or will lower free draining ground be good enough. The grating at the higher ground level could be the same as those used for channel grating, all you need is a support for it. Some galvanised angle may well be enough along the wall. the drive side can be the top of the block paving concrete restraint you would need to put in

If you use channel, fix as per manufacturer advice. Some may need to be set in concrete. If tight against the house use a strip of fibre board or similar inbetween about 10mm thick topped off with a sealant would be ideal. Maybe setting the grating at the higher level as mentioned above