# Forum Home Renovation Flooring  Self levelling compound over waterproof membrane.

## jack36

I am replacing an outdoor deck in the courtyard of my strata terrace.  The deck sits on a concrete slab that is common property.  The slab has been covered with a waterproof membrane.  The slab has not been levelled properly and water drains away from the floor waste and pools.  I would like to know if I can use a self levelling compound on top of the waterproof membrane to prevent water pooling and push water towards the floor waste.  The whole area will be covered by timber joists and a new deck so I do not need a perfect finish.  The inadequate draining and use of non treated pine joists and bearers caused the current deck to rot in 3 years!  Any advice would be greatly appreciated.

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## Oldsaltoz

Should be no problem, just make sure it's suitable for outdoor use, some do not like UV light and may degrade. The suppliers should have the data sheet information. 
Good luck.

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## Kwikee

How much build up/fall do you have to the waste? If you can build up 25mm at the lowest point, you can use a sand & cement screed, mixed up about 10:1 sand:cement, just damp enough to bind together.  Prime the surface with Bondcrete, then spread the sand/cement, pack it down and screed to the required fall.
otherwise, you can use self levelling compounds but they tend to self level (fancy that?!) and not work to the fall, or crack when too thin or thick.

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## Oldsaltoz

I suspect a screed base would be very porous and redirect any heavy flow.

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