Very damp clay soil along back of house

[chameleon001]

Hi,

Have been finding varying levels of water under my house, suspended floor with crawl space/ concrete base. Varies between none to 1inch and seems to depend on rain etc. I have found a small crack in the foul waste pipe too. I poured drain dye onto the soil along back of house and got loads of water/ dye under house. So I'd like to stop this if possible. Was thinking of digging a channel along back of the house and installing a French drain as well as repairing crack in the clay foul waste pipe. Does that sound like a reasonable plan to reduce the water ingress?


Here's a pic of under the house after dye poured onto soil around house.

Cheers,

 

[Nige F]

You may find there are other cracks in the foul drain. I would uncover it to the manhole and then test or replace. You may not need a french drain when the foul is repaired.

 

[Ian H]

Have you got a few colours of dye? You could do with different colours in different drains first to see exactly which need attention.

 

[chameleon001]

The drain leak is only tiny, a significant amount is just groundwater by the looks.

 

[Hugh Jaleak]

That is a lot of dye for a 'tiny' leak. As Nige has said, repair the drain first, (that needs to be done anyway!), and review the situation then. If there is still an issue with water ingress, time for plan B.

 

[Nige F]

I see you dyed the groundwater - so you can crack on with the french drain it can only help. Maybe consider replacing the airbricks to the underfloor with modern plastic ones, they have a better airflow.

 

[Doggit]

What's the difference in height betweem the outside ground level, and the inside void; and as you've got a concrete base, how do you think the water is coming in. It's possible that a french drain may not be sufficient, as it'd only take the surface water away, and you need to install a land drain instead.

 

[dilalio]

Also, is there a slope to the ground at the back of the house that runs downhill towards the property? I.e is the property set into a slope? If so, it'll all be coming your way and you may need to dig a sump in the basement and permanently have a pump in it with a flow switch and drain pipe to rainwater drain to evacuate it.

But, the leaking underground should be priority. Have it out and replace with plastic.

 

[chameleon001]

Hi yeh the dye was poured onto the surrounding soil so represents the ground water. When I dyed the drain a few weeks ago I got less dye under the house. I reckon there's about 2 and 1/2 foot between ground level and the concrete base. Garden flat but the old patio was sloping towards the house (another job to sort!)

 

[dilalio]

So now you also need to determine if it's ground water or surface run-off! Is your dpc intact and high enough?

 

[chameleon001]

Yes dpc well above any moisture

 

[chameleon001]

I'd say surface water as when weather is dry the water under house goes away, then returns when heavy rain

 

[Doggit]

But if it's surface water, where is it getting in. You've said that the patio slopes towards the house, but would levelling that alone cure the problem. You also said that there was a difference of about 2ft between the ground level and the concrete base, so do we assume that the concrete base is lower (just to make sure) and if it is, then is the water coming from the sloping patio, or the porosity of the bricks against the outside soil. Now having the patio, is it just on the surface of the ground outside, and is the water coming in through the soil underneath it.

Or have I completely misunderstood the layout.