View Full Version : Stormwater leaking into basement
20th Apr 2012, 03:19 PM
Not sure if this is in the plumbing or structural domain but would appreciate any advice...
We have a semi dettached californian bungalow with sandstone foundations which is on a sloping block. About 18 months ago I ripped up all the concrete that was covering all the ground area around the house and replaced with grass. Since doing this we have a problem with leaking water into the basement, usually it isn't that bad but with the wet summer it has now become a problem and has destroyed a lot of our stuff in storage and increased the damp significantly. The water seems to come through the sandstone blocks in the side foundation, have attached a few pics for illustration.
Anyone have any advice where to start with this?
this is the side of the house before the topsoil and grass went down.
this is an elevation of the house showing where it is coming through into the basement.
20th Apr 2012, 03:58 PM
A nice impermeable membrane to divert rainwater away from the foundations and sub-grade sounds like a good idea. I'd suggest concrete, maybe some sort of concrete path or something? Dig down a bit and get rid of loose topsoil and stuff, it's too water permeable; get to some nice hard packed earth and concrete over that and that should help it all dry out.
20th Apr 2012, 05:55 PM
Would be good to see a close-up and another angle of that downpipe connection, from here it looks like a level inlet from a d.t.
20th Apr 2012, 11:31 PM
You need to confirm the location of the water entry before you do anything else.
That down pipe looks a bit like a cast iron job, prone to corrosion and leaks at joints.
If you are confident it is just seepage through the sand stone blocks you a couple of products that be applied inside or outside.
They are called Krystol and C-1, both are designed to grow crystals in the block work or concrete. It needs to applied 3 times, one week apart.
Application is very easy, just identify the area/s to be treated. Mix about a litre (or half that the first time).
I use ice cream containers because they are easy to clean between batches. mix the powder with cold water and mix to a slurry consistency and apply to the area with a car wash type sponge, you only need the thinnest cover as you will be adding 2 more coats.
Any cracks or joints can be filled in, but do this only when hour batch has almost run out, because by this the mix will be stiffer and warming up in the container. To ensure a good seal over cracks and joints, use a small (10 to 15mm) round bar placed along the crack/joint and hammer some of the product into it, this action can stop running water in it's tracks.
Leave this for a week to allow time for the crystals to grow. and replete the above, than again a week later.
You will see a drastic reduction after the first application, leaving a few damp spots that are easy to see as they are a bit darker than the rest.
Your second application will most of the above leaving only a few small areas to treat with the final application.
This stuff was used in the USA to stop a leak on the dry side of a dam wall with 25m head, so your storage area should be a doddle.
Good luck. :)
PS. using and external plastic sheeting will not work on a sloping site because the diversion at the top allows water to pass under the wall, this wall is higher then your storage area, so it's very likely the water will continue to enter.
21st Apr 2012, 08:19 AM
Not at all surprising given the hydraulic conductivity of sandstone! I'd check that downpipe too, but for a better solution you may need to drain the back of the excavated area under the house, if it's not been done already. I wouldn't necessarily blame the grass either- the last two summers have been rather wet and a lot of the water that comes down your hill is going to come from upslope (ie from the front boundary fence side), where it infiltrates on neighbouring properties and flows through the soil to your place. If your house is sitting on a sandstone shelf or a subsoil of clay or something similar, this water finds it easier to flow horizontally down the hill instead of vertically to the water table. Is there a way that you can better ventilate your basement?
21st Apr 2012, 12:56 PM
:whs: you shouldn't assume where the water is coming in, but it will always be flowing from the highest point to the lowest and through the soil too. So most likely there is poor or no waterproofing between the soil and all that section of stone wall under the soil - sides and back. Of course it might be a matter of that down pipe and soaking through fully saturated soil every time it rains again - you need to do some more investigation else any attempts to fix will be just a waste of time and money.
23rd Apr 2012, 04:50 PM
Thanks everyone, sounds like I have some digging to do either way, will have to wait until I finish my temporary kitchen...
The pipe in the photo is actually a sewer vent although I wonder in the past when they installed the sewer line would they have just cut through the sandstone foundations, maybe this is an entry point.
6th Aug 2012, 12:43 AM
Finally got around to digging this area out, turns out where they have installed the bathroom plumbing in the past they had removed a block and just filled it in with soil which was providing a direct path for the water to get into below the bathroom and then down into the storage area.
Old pipe is now replaced with pvc and I have filled the void with concrete so should help, along with all the other waterproofing I'm doing at the same time.
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