# Waterproofing a flat roof



## xgarb (May 6, 2011)

Anyone have any products they recommend or have had a problem with for waterproofing a flat roof?

The best way here (Andalucia) appears to be using fibreglass sheets with a sealant. I have had a few quotes for this but they were a bit expensive for something I think I can do myself with a simpler technique.

This product has good reviews: https://www.leroymerlin.es/fp/13976...-humedades_pintura-impermeabilizante-exterior or different brand: https://www.leroymerlin.es/fp/15243...des_impermeabilizantes-cubiertas-suelos-muros

A possible alternative but I'm concerned it will end up being a sticky mess: https://www.leroymerlin.es/fp/18688...zacion-tratamiento-humedades_silicona-liquida

It's a stop-gap solution because in a year I want to put a second roof a few centimetres over the existing roof with plastic base to make a green roof with small desert plants or similar.


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## Nomoss (Nov 25, 2016)

We had a problem with a concrete roof with a very gentle slope, where the rainwater soaked into the concrete and then into the wall at the low end, causing the yeso to soften and eventually start to fall off.

It was permanently solved by covering it with bitumen felt, sealed at the joints with hot bitumen (blow lamp), with a cement screed of about 4-5 cm over.


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## baldilocks (Mar 7, 2010)

Don't do what the guy (a Brit) a street or two away did. He got a waterproof membrane and nailed it to the existing roof - water just leaked through the nail-holes puncturing the membrane. We could see him doing it since we are a little higher than him.


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## Mark s (Jun 6, 2019)

Try a product called acrypol. It’s a fibreglass brush on roof coating that should work. It’s quite expensive tho but may be cheaper than other methods.
Good luck


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## davids0865 (Apr 12, 2016)

Mark s said:


> Try a product called acrypol. It’s a fibreglass brush on roof coating that should work. It’s quite expensive tho but may be cheaper than other methods.
> Good luck


Wow, just checked £2000 to paint my roof


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## Barriej (Jul 23, 2012)

While we were over in October i had to help the father in law with the same issue on his flat roof.

We used Caucho con Fibre which basically is a thick rubberised paint. Don't buy the cheapest available its not very weather proof.

Most of the good stores will have it 
Google will be your friend here and you can get more info on the paint.

Here in the Uk I used Thompsons Bitumen roof paint (same sort of stuff) and it works well for a couple of years.


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## Nomoss (Nov 25, 2016)

The problem with easy paint-on products is that few, if any, stand up to the high level of uv in Spain, and will peel off within a few years or less.

The roof on our old house in Spain which I mentioned in my post above, had the bitumen felt + cement put on in about 1983. We sold the house to friends, and on our last visit to them a couple of years ago all was well.

At least, I think they might have mentioned if the roof were leaking


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## Alcalaina (Aug 6, 2010)

We apparently have a waterproof membrane under the tiles, no idea what state it's in. We bought the house in 2005 and it's never leaked. Every four or five years we repaint the tiles with caucho (a rubber-based emulsion which everyone uses here). 

It now comes in green as well as the traditional red. Ours was the first house in the village to have a green roof terrace and now they are popping up all over the place.


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## Alcalaina (Aug 6, 2010)

davids0865 said:


> Wow, just checked £2000 to paint my roof


Use caucho, less than €300 for a 70 m2 roof.


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## Megsmum (Sep 9, 2012)

xgarb said:


> Anyone have any products they recommend or have had a problem with for waterproofing a flat roof?
> 
> The best way here (Andalucia) appears to be using fibreglass sheets with a sealant. I have had a few quotes for this but they were a bit expensive for something I think I can do myself with a simpler technique.
> 
> ...


When we moved here five years ago we had a leak through our roof terrace. We had a company come and paint some stuff on, like a membrane absolutely brilliant, the following year we tiled over it. Husband is out but we have a tin of the stuff somewhere. I’ll post on his return


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## xgarb (May 6, 2011)

Thanks for the all the replies. I'm up to 6 methods for doing this that I've seen in the retailers or at friends' properties

1) Bitumen felt + hot bitumen to seal
2) Plastic mesh with thick white paint (maybe guacho)
3) Fibreglass rolls with resin
4) Paint with fibres
5) Waterproof membrane glued down
6) Launa https://es.wikipedia.org/wiki/Launa

I think I've going to go for the paint with fibres because it's the easiest and I plan to put a second roof above this with a 5cm gap for insulation using something like the image below and try to create some sort of green roof.


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