# Forum Home Renovation Tiling  Waterproofing before or after screed on concrete floor

## bodomad

Hi all, 
Renovating my bathroom at the moment. 
Have removed sub floor, redone underfloor plumbing and poured concrete roughly 60mm below FFL. 
Just wondering if its better to waterproof before or after the screed. 
Also is there a product I need to put down first to block moisture coming through the concrete? 
TIA.  
Adam

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## sol381

Before.....Only time ive seen it done after is on the block..enough said...

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## bodomad

Cool. Thanks sol381. 
Do I just put the waterproof membrane directly on the concrete? No primer?

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## sol381

Im no expert ive just seen what my guy does.. You need puddle flanges as well i hope you know.. Im sure you just waterproof onto the concrete tho..

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## goldie1

> Cool. Thanks sol381. 
> Do I just put the waterproof membrane directly on the concrete? No primer?

  It depends on the product you are using . Read the instructions. 
Waterproofing is commonly done before the screed as its quicker. There is no reason it can't be done 
after.  If you have the time to let the screed dry properly doing it after is a better job. 
When its done before the screed is constantly wet which is why many bathrooms have  
a musty smell.

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## phild01

You have the time and best to do it after screeding.

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## bodomad

Thanks phild01, 
Decided to do it after as im in no rush. 
Ill be putting Kemcrete down before screed for extra piece of mind. 
Also do you know of a screed calculator? ie bags of cement, sand etc

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## phild01

It's best to do it after as the screed is kept dry during shower use.  Beware not to use a screed that is too wet and do let it dry out well.  You want to ensure the screed does not crack as it dries and don't use a mortar mix.  The pros usually waterproof under the screed simply because of their timeframes. They need to get on with it and don't want to be waiting for a screed to dry out.

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## CStenhouse

If your on a slab, you can screed and waterproof on top once all moisture has escaped (roughly 2/3 days depending on the weather. ALWAYS waterproof on top otherwise the water from your shower will eventually break down the minerals in the screed and wash out the binding components. You will also get efflorescence caused by h2o reacting with the minerals in the screed. You can also waterproof underneath if you experience negative hydrostatic pressure with an epoxy based primer or waterproof. ALWAYS membrane under and over if tiling over a timber floor.

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