January 20, 20188 yr Hey all! My 'flat' roof sits above a living area and the architect wants a drainage channel on it to keep water away from the above ground build. The problem he has is that any channel will not be a water tight fit around it i.e. poured concrete around it. I take his point but can't see an easy solution apart from trying to cast 'in situ' a drainage channel i.e. no joints. He means literally the mm gap (or less) between the channel edge and the poured concrete. I certainly can't find a drainage channel with a 'flange/lip' that allows poured concrete to go over it - so I guess I'm looking for something that doesn't exist and hence is wrong!!! My *current* solution is to embed a plastic pipe wrapped in polythene in the roof (held in position by rebar etc) . Then once the pour has cured pipe (in theory) should just pop out and I have a nice smooth no joints channel. This is a separate issue to my waterproofing! and walk on glass issue! Any suggestions appreciated!
January 20, 20188 yr We have a concrete parking slab next to the garage (which will eventually be covered with a car port) The builders were concerned rainwater might end up sitting against the garage wall. So they made a cast in place drain "groove" by setting a piece of pvc gutter into the concrete while it was still wet, weighted down with stones, and tapered so it was deeper at the back where it will drain off. There was no need for plastic sheet or anything. Once the compo had set, the pvc gutter lifted out leaving a very neat channel. I can't post a picture as it's currently under 4" of snow.
January 20, 20188 yr Author 9 minutes ago, ProDave said: We have a concrete parking slab next to the garage (which will eventually be covered with a car port) The builders were concerned rainwater might end up sitting against the garage wall. So they made a cast in place drain "groove" by setting a piece of pvc gutter into the concrete while it was still wet, weighted down with stones, and tapered so it was deeper at the back where it will drain off. There was no need for plastic sheet or anything. Once the compo had set, the pvc gutter lifted out leaving a very neat channel. I can't post a picture as it's currently under 4" of snow. Thanks! I did think of this but was *worried* if I couldn't push the guttering down or it sank too much! With either method I would still prefer waterproof concrete (though my architect thinks thats a waste of money) ; so not sure of the additional cost compared to a standard pour. On top of this I have to have an EDPM layer (as far as I can tell) because we have 4 walk on roof lights so the 'edge' around them needs to be water tight. I guess my architect assumes the EDPM will be enough and hence no need for water proof concrete!. If I did go for an in situ channel I think for peace of mind I'd paint it with water proof sealant or something. Edited January 20, 20188 yr by pocster
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