Basement dampness problem

[shellac]

Hi Folks
I am not sure if this is the right forum to post my problem? I have a dampness problem in a basement room that is 900mm below ground level. Construction is brick and concrete floor. The problem occurs after it rains. It starts along one wall leaving a 2 inch wet patch on the concrete floor and progressively gets worse until the entire circumference of the room has the wet patch.
The lower bricks have a crusty white substance on them. The room has one outside wall.
Can anyone suggest what I can be do to solve this problem?
thanks

[skot]

You may have to remove the soil away from the wall and tank the outside of the wall with waterproof membrane. Dig down to below to level of the floor..possibly 250mm below the floor and run an agricultural drain away to a lower point then backfill with gravel to about 100mm below original level.

Then you can replace soil and turf or garden back to origianl level.

When you are getting water into a room like that, there is no quick fix that will last.

[joe greiner]

What he said, except for replacing the outside ground to original level. Outside ground should slope away from the house at about 5 percent slope for 3m, if possible. If not possible, you may need to install a retaining wall and separate drainage system to divert surface water away from the house. Also, if eaves are less than about 300mm, gutters and downspouts should be installed to reduce rainfall from the roof contributing to the problem.

Joe

[shellac]

Thanks Skot and Joe
I have started the dig. Installing an ag drain below floor level will be a problem as I have no where to drain it to.

I am thinking I will just waterproof the bricks and put up a membrane and backfill with soil. What do you think?

I dug up a field drain about 400mm down but its about 800mm off the house, still it must be removing some of the water. I dont think I have a problem with surface water as the land at the side of the house slopes from front to back but I will build it up so there is a fall away from the house. Gutters and downpipes are installed.

[echnidna]

If you can't get the fall to run a normal drain you need to run the drain into a pit with a float swtiched pump. Then you automatically pump the water to a suitable discharge point

[joe greiner]

I'd avoid the sump pump if at all possible, because it brings its own maintenance problems. If the fall of the land allows, add a few extra lengths of pipe to bring the drainage around the sides of the house, to daylight or a passive French drain. Add cleanouts with surface access at any elbows to facilitate flushing when/if necessary.

Joe