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sealing a porch

PostPosted: Fri May 08, 2009 12:11 pm
by linda waghorne
Please help, I built a concrete base for a upvc porch which was not evenly laid, when the porch was built on top there is a surround of about 1ft all around.
I have tryed sealing the bottom by filling in underneith where there is a gap and making a lip of concrete all around the edge. I ended up getting water in the porch when it rained so I then got a sealant and put that all around inside and out but I am still getting water in, what can I do to stop the water coming in.
As you can guess I am no DIY person just trying to do this myself as i cant afford to have someone do it for me.
PLEASE I NEED HELP & ADVICE>
Linda

Re: sealing a porch

PostPosted: Sat May 09, 2009 12:13 am
by barrie
you could try putting a self adhesive lead flashing round the outside so that it covers 2inches up the porch and the rest gos onto the cement that you have put round on the outside you can get this in b&q

Re: sealing a porch

PostPosted: Sat May 09, 2009 9:13 am
by John Gallon
Hi Linda,
Was the concrete perfectly dry when you applied the sealer and did you use silicone sealer?

You could lay a water proof screed over your concrete base if you can get a minimum of 25mm depth (no less) laid on a coat of external pva. This will make your internal floor higher than the outside concrete and will also even up your "not evenly laid" base. If you put any sealer, lead flashing etc on the outside make sure you don't cover any drainage holes in the upvc frames,

Re: sealing a porch

PostPosted: Wed May 13, 2009 11:41 am
by Norman
Hi Linda, it sounds like what is happening is rising damp, I’m sure you have heard of this before, well due to the brickwork being on the ground (known as wet wall) it will get damp or wet and due to a capillary action the water can be draw in and up a vertical wall up to a meter high before the water is to heavy, thus why rising damp only effects the lower meter of your house. You need to incorporate a DPC (damp proof course) this is normally at floor level or 3 bricks high, however most PVC installers remove any DPC & their argument is that the window is plastic and to be fare a DPC is only a strip of heavy gauge polythene, but one thing they forget is they drill out through the bottom of the frames and water drains out the fixings onto the brickwork instead of draining out the draining holes at the front of the frames so its fare to say any brickwork, cement pointing or anything else you put onto such brickwork will always get wet due to capillary action.

How to over come this problem is to form a water proof membrane ideally under the floor and to a level above the bottom of the PVC frames.

Norman Dowie
Swindon


Your other responses won’t work
1.
You could try putting a self adhesive lead flashing round the outside so that it covers 2inches up the porch and the rest goes onto the cement that you have put round on the outside you can get this in B&Q

This will fail as it will be stuck onto brick that are known as wet wall so it will still draw the damp from the ground.

2.
Was the concrete perfectly dry when you applied the sealer and did you use silicone sealer?

You could lay a water proof screed over your concrete base if you can get a minimum of 25mm depth (no less) laid on a coat of external pva. This will make your internal floor higher than the outside concrete and will also even up your "not evenly laid" base. If you put any sealer, lead flashing etc on the outside make sure you don't cover any drainage holes in the upvc frames,

This will fail as it will be stuck onto brick that are known as wet wall so it will still draw the damp from the ground, and these kind of external pva’s have a life span before they start to fail too.

Re: sealing a porch

PostPosted: Wed May 13, 2009 6:06 pm
by John Gallon
Hi Linda,
I don't know which post Norman is reading but in your original post there was no mention of brick walls or rising damp, just a problem when it rains.
I read your post/query to mean the PVC porch frame is fixed directly to the concrete base which is about 1ft wider all round than the porch.
The reason for the ext. pva is that with only the depth of the PVC frame you wont have enough depth to lay a full depth concrete screed with a dpc membrane and your only option would be a thinner screed keyed to the base with the pva,

John