I’ve recently made our internal flooring downstairs far more airtight to help maintain temperature indoors.
On the outside I’ve taken up rotten decking witht a view to building some raised beds, to find a mix of concrete and soil by the house walls. I’m wondering what best to do to help avoid drainage issues by the house wall especially since the space under the suspended floor is less ventilated now (we do have air bricks, but had bare floorboards before that were really draughty)
The lowest level of bricks look a bit damp, have algae growing on some of them both on the soil and concrete bits, but think they are all below floor level.
Do people think I should do something to drain water away from the house? What would be doable safely around the soil pipe? I’ve got some spare pavers from other bits of the garden, i was thinking of paving the parts close to the house walls with a fall to encourage the water away from the house
If you haven’t had any groundworks done that reveal the footings then the only way to find out is to dig a hole. There are ground scanning devices but the cost is prohibitive to most mortals.
The reason I asked is to check that any suggested drains don’t go lower than the footings.
Good, that’s a good sign.
Clay can hold its moisture for a very long time before becoming rock like, which may not be any good for your dampness issue. Then when it eventually rains the rocklike clay hardly absorbs any water until the surface is well moistened, so even if you don’t see pooling after heavy rain there is almost certainly a film of water on the surface. That isn’t good for your dampness either.
My opinion is that you might need a French drain along your wall. In relatively free draining soils that would be adequate but for clay like soils you probably also need a soakaway away from the house. That also means that a proper drainage profile will be required for the bottom of the drain. That isn’t particularly important for free draining soils.
Don’t pave over the drain. You can make it look pretty by using a top dressing of attractive small stones.
Thanks for this advice! I did think about something to drain surface water down away from the level of the crawl space, like digging a narrow trench by the wall and filling with chippings. Do you think that would be better than paving to drain water away from the walls / doing nothing?
The problem is its really hard to dig in our ‘garden’, its why I wanted to build raised beds for planting. The concreted bits are obviously a no-go. The exposed ground around the soil pipe is maybe 80% old bricks, I think it must’ve been paved in bricks once and has since been filled in. So digging a trench through it for a drain away from the walls is really hard. Even digging a trench against the wall around the soil pipe feels dicey, really dont want something to shift and end up with sewage leaking! maybe thats me being unduly nervous.
This is all in the context of the clay being really hard to dig out, and not really wanting to disturb the ecosystems that have already vaguely made their way through the mess thats under there.
I might try digging out a trench by the wall today and see how it goes, then go from there
A land drain against your wall will effectively lower the level of wetness to near the bottom of the drain except perhaps when it’s raining hard. Paving at an angle away from the wall raises the level of wetness to the top of the paving.
Even better than the drain would be to treat the exposed wall below ground level with a breathable waterproofer before filling.
