Dot and dab onto tanked wall?

2 Jan 2013
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United Kingdom

I'm in the process of renovating and have come across a wall with some damp. Can I apply a tanking slurry like Vandex BB75 and then dot & dab plasterboard to this?

Apologies if this is a silly question, but any guidance would be welcome!!

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I can't see anything wrong with doing this, except it may be better to use polystyrene backed plasterboard.If you have definitely cured the damp then use 20mm finished polyback/plasterboard dabbed on with board adhesive.If you are boarding around a corner make sure you run the board into the corner and trim the plasterboard off so the polystyrene runs into the corner and the next board runs into it without the plasterboard touching the wall, Or you could stick some 6" or 9" DPC inside the corner and run your boards into that. Hope you understand this. ;)
Insulated board will also stop you getting cold spots that are damp where the dabs are.
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Heres what we did when we tanked a room that suffered from damp

1. Chipped all the old plaster off the wall (Very messy job)
2. Had the brickwork skimmed with cement for a more even surface for the tanking to coat.
3. After the cement dried, tanked it (two coats in opposite directions - up and down, left / right strokes) This ensures you wont miss anything.
4. We then decided to dot and dab plasterboard over the tanking (Leave an inch gap from the bottom of the plasterboard to your floor) This will allow air to circulate and stop any damp that may come from the floor upwards get into your new plasterwork.
5. Had the plasterboard coated with plaster finish.

This was almost 3 years ago and touch wood, no damp has come through.
You could contact a few companies who specialise in tanking to double check, i am only posting what worked for me.

I was led to believe (by professionals in my town who give me a quote) that plasterboard is seperated from the wall with the dot and dab creating an extra cavity as such allowing air to dry any moisture and providing you with an extra meths of insulation??

Some info can be found
Forgot to mention,

If your looking to buy tanking, its quite an expensive product.. Check ebay out (Thats where i bought mine from, was a big saving, even with delivery charges)

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