leaky conservatory and french drain? help!

H

honeyanan

Hi, we live in a quasi-semi where the ground is higher at the back of the garden and slopes towards the house. The garden is in three levels: the back (veg patch and shed area), the middle (patio, lawn and walkway) and front where it used to be a messy concrete area. The back the middle parts are fine. The front concrete area used to slope towards the house and had an outhouse on it.

Over a year ago, we decided to get rid of the outhouse and had a conservatory built across the whole width of the house--our neighbours had one identical, and never had any problems, so we went ahead, too.

Then we realised the problem. Because the whole ground is higher at the back and lower at the front, while the conservatory is at the same level as the kitchen floor inside the house, when you get to the outside, the concrete starts at the same level as the damp-proof membrane of the conservatory and slopes upwards. In other words all the rainwater was running towards the conservatory.

We know that the outside ground is supposed to be two bricks lower than the damp proof membrane. So we started digging...

Then we realised that once we have taken out the huge chunk of the concrete ground, we are left with a huge "lake" that is the lowest point of the garden, even lower than our neighbours' . We live on heavy clay soil where drainage is poor in general. The grass and flowerbed is always soaking wet after rainfall. Now it's even worse--all the runoff is accumulated in the "lake" we created. Our outside drain is by the original outside wall at the back, and is somehow higher than the "lake" we created. I also checked the water-level in the drain, which seems to be the same level as the water in the "lake". What I'm trying to say is, there is no way we can install a parallel drain system to divert the rainwater.

So our thoughts were to put a french drain at the back end of the (what used to be) concrete area, across the whole width of the garden. Meanwhile make the base of that area slope away from the conservatory...

I am posting this because I am not sure if this would work. But I can't think of any other options.

My other question is, ever since we started digging the "lake", we have been seeing wet patches on the conservatory floor, which is still concrete with damp proof membrane underneath. The wet patches appeared right by the external wall. Is this because the whole conservatory is sitting in a pool of water so water just seeped in? or could it be some more serious problem? It's our first house and first every building project so I'm getting quite worried...

Thanks in advance for any advice.
 
Sponsored Links
Joined
3 Feb 2008
Messages
7,797
Reaction score
1,951
Location
Northamptonshire
Country
United Kingdom
Basically seems the water table is very high, with heavy clay soil, its not unusual....

The drain at the rear, does it take the rainwater from the roof?
 
H

honeyanan

yes it does. The rainwater from the gutter drains down to the gully at the back of house, behind the kitchen wall. but the conservatory is built across the whole width of the house, leaving only 20 cm space to the next door's fence. To get to the gully you'll have to squeeze yourself through the 20 cm gap...
 
Sponsored Links
Joined
3 Feb 2008
Messages
7,797
Reaction score
1,951
Location
Northamptonshire
Country
United Kingdom
Ah. Maybe need a thin builder then..... My thoughts would be to install a french drain across the back, at a suitable depth to protect the building, and discharge this into a sump. To drain the sump, fit a submersible pump, type with a float switch so its cuts in as needed. Pump the water away into the rainwater gulley from the roof. (Assuming this doesnt go into a soakaway. Not likely I wouldnt have though as the ground doesnt lend itself to being porous!)
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Top