Flat Concrete Roof Leaking?

[podgey]

Hi all, i recently bought a house with a flat concrete roof. It looks a bit weird, but is a really good space with an excellant view. The only problem is that the big bathroom tiles that cover the roof are leaking water in a couple places. Can these be resealed easily? Or would i have to redo the whole roof?

Another thing i was thinking about was to build a roof over the whole lot. It would have to be light wieght, but strong enough to withstand stong wind. So i was wondering if anyone one has experience with colorbond roofs or knows a good company in LOS.

Also i have seen photos of 'green roofs' that look interesting, thats where you grow lawn on your roof. Maybe i could build a driving range?

Your thoughts and ideas would be apreciated.

[trogers]

Big bathroom tiles? These are probably added in by a previous owner, and not the original owner who got the house built. Most likely the flat roof is waterproofed with a membrane and it is worn and leaking. It is this layer that needs replacing, after removing the tiles and cement screed.

I doubt your house structure can handle the load of planting soil (2000 kg/m3) for a green roof. Best you can do is to place a layer of artificial turf on top of the new waterproof layer.

Using roof sheets as a rain barrier will not work unless you are prepared to change the profile of your house with a pitched roof.

[Rimmer]

Flat roofs always leak sooner or later. The water Is probably pooling against the edges or corners. If so can you cut a drain with a pipe to take it away? Then seal the edges with the Silka roof tape.

Is all the grout in place in the tiles? If not you can try re grouting with a waterproof ad mixture in the grout.

Not very satisfactory I know but short of stripping off all the tiles and renewing the water stop membrane not much you can do.

[Artisi]

If your "flat roof"is like any other flat concrete surface in Thailand it is probably far from flat. The low point is probably in the middle of the roof and the roof is more than likely not got any "fall" on it to ensure drainage.

It amazes me that for a country with such high rain fall that flat roof's are even considered as viable.

[podgey]

Thanks for the input people, i will take it all under advisement. I'll look at recaulking first and if that not succesfull, rip them bloody stupid tiles up.

[quiksilva]

FYI we usually consider flat roofs to have a useful life of about 10 years.

Regular maintenance to ensure that drains / guttering is unblocked is essential, to prevent ponding which can result in leaks and may even require the entire roof to be replaced.

If you do resurface the roof ensure that they maintain at least some slope to prevent ponding.

[katabeachbum]

Installing tiles on a flat roof normally makes it leak more. Tiles are not waterproof, neither is grout. Water remains in the concrete, not allowed to evaporate.

I would remove tiles/glue/cement. If the concrete has no cracks, continue with checking slopes to drain and drain capacaty. If all thats ok, time for membran. Sika has some good products.

If you want to use the roof, now its time for tiling. With glue to keep the weight down.

Flat concrete roof can be build waterproof. To do so , I use CPAC readymixed 280 Waterproof (ganzum in thai) minimum 15 cm thick with dual rebar layers. Several large drains and good slope, at least 1;100.