Garage roof problems

[Ken57]

Hi all

I have an old (1950s?) garage roof that's prone to leaking, so I'd be glad of any advice on my options.

You can see what it's like from the photos, inside:

top: inside, the roof seems to be made up of concrete beams arranged like floorboards, with joins in places that make me wonder what they're attached to.

From on top, it looks like crumbly concrete covered in various layers of patching and gunge, (some of which I've just peeled off as it was detaching itself), with several breaks in the level.

From inside there appears to be a consistent slope, but from on top it's a much messier proposition.

Can anyone tell me a) how the roof is likely to be constructed (and what's holding those beams up?) and b) what options I have for making the thing reliably waterproof?

TIA Ken

[Harry Bloomfield]

Ken57 explained :

That looks very like concrete poroured in situ, which was supported by floorboards whilst it was allowed to cure. The mess on top looks as if it was once covered in pitch to provide waterproofing to the concrete, later patched with the grey material.

If the concrete looks serviceable, then just get a flat roofing specialist to take a look at it.

[The Natural Philosopher]

Mmm. It may well be in which case its probbaly got steel reinforcing in the lower part of it.

I suppose you could sort of lay down timber on props, with maybe a pklsatic sheet over it, then lay a shallow layer of concrete, then put dwon renforcing mesh, and then pourt a deep mix - probabably 6 inches or so - to form the roof.

Seems bvery expensive though. These days you use bolck and beam I would think.

The top surface will have be totally broken up by frost shattering if teh waer oproofing has failed.

.

I have another suggestion. Lay a DPM and some poly sheet ob it and add another few inches of screed, to get a bit of insulation, then cover the lot with tarred felt stuff.

Or just screed it to a decent slope and put down tarred felt anyway.