Bay window damp and insulation issues

15 Dec 2008
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United Kingdom

I hope this is the appropriate forum as this issues involves, rendering, carpentry and bricks.

I have a bay window wall which has got blown plaster. The plaster was blown when we moved in last year but I've just gotten around to hacking it all off.

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You can see the bubbling of the paint and the salts on the underlying brick.

The wooden window cill looks to have been laid directly onto the brick with a layer of mortar underneath - no dpc - which is likely the reason for cracks in the wood on the top surface.

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I've removed all the plaster and now I'm trying to decide what I would like to do and the best order to do things.

We live on a hill so there is no drainage at the front, the guttering runs to the back to connect with the downpipes but there is insufficient fall on the guttering at the front which means in heavy rain it overflows and I believe the splashing of the water on the ground is contributing to the damp. This will require scaffolding to remedy as there is a garage at the side with a polycarbonate roof.

There is also a concrete slab around the exterior of the bay that is level with the bituminous dpc. I'd like to remove this to improve drainage but I'm a bit apprehensive as I have read that many bays in 1930s houses don't have very deep foundations. Perhaps the slab was added to prevent any movement?

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Since the walls are solid brick, I'm considering a sand-cement render with a waterproofer in it and then insulated plasterboard on top of that. I would need to replace the wooden cill to cover the top of the plasterboard. I'd have a dpc placed under the replacement cill. I could then have the plasterboard skimmed.

Anyone followed this approach? Thanks
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