Garage roof suggestions

[Syke]

I have a double garage with a flat, corrugated cement/asbestos roof. This is quite old and leaks extensively. I've tried sealant at the joints but without much success, leading me to think that some of it may have become porous. Last year, while having work done on another flat roof, the contractor offered to brush tar over the garage roof, but this has had little effect.

I had a roofer look at this recently and his suggestion was a wooden framework first, followed by a plywood deck then several layers of roofing felt, in effect a flat roof built on top of the existing one. His quote for this was, I felt, far too much, and I wondered if there might not be a better/less expensive way forward. Any ideas?

Regards, and thanks in advance

Syke

[JimK]

steel roof sheeting? JimK

[Harry Bloomfield]

Syke laid this down on his screen :

As per Jim K - steel sheet roofing. It's not the old style rounded corrugations but more of a squared off type. They are galvanised then painted. Cut them and the galv is supposed to run around the cut to prevent the edge rusting. They are tough, very light and not expensive. Their only down side is condensation on the under surface, so it either needs to be bought with insulation or insulation added.

[spamlet]

At the risk of sounding silly, why is the corrugated roof flat? The whole point of the corrugations is to allow the water to run down a controlled slope into a gutter. If the corrugated sheet has been put on flat, the water can't really do much else but evaporate or soak right through, can it! You need to raise one end so the water can run off.

S S

[Harry Bloomfield]

I'm fairly sure he meant a relatively flat roof.

[Syke]

is a fall.

Syke

[Nightjar]

There is a selection of alternatives here:

was used by a friend to roof a garage with great success.

Colin Bignell

[NT]

Maybe a pic would give some clues as to why its leaking. If you needed to rebuild you might even reuse the asbestos replacement sheets, if that's what they are.

NT

[spamlet]

Right, so, have you been up and scraped all the moss out of the grooves, so that the water does not collect behind it when it rains? And have you checked inside to see where the water is actually coming in? Favourite spots are behind said balls of moss; down the hangers/bolts and through cracks that you may not be able to see v well until they get wet; and over gutters that are full of leaves - as is the down pipe itself v often. Failing that, it may be that your prevailing wind is in the 'up slope' direction and the slope isn't sufficient to prevent the water blowing back enough to travel sideways under the joins. Either way, if you can clean the roof enough to get a coat of mastic to stick, water can't really get in after that, especially as the sun will melt it into any new holes each year.

S >

[Harry Bloomfield]

spamlet pretended :

I'm thinking to run some bare copper wire over my roof as a means to keep the moss at bay. Might this work?

[spamlet]

Don't know Harry.

They do, as you know, use copper and even ferrous sulphate as moss killers on lawns (and zinc sulphate if you can find it, works a treat on mould in bathroom plaster), but whether the 'verdigris' that would eventually develop on your wire would have a similar effect, or even whether the wire surface would passivate and not dissolve at all, I don't know: it could require acid rain! Nor do I know whether the sort of moss that grows on lawns is remotely related to the stuff that grows on rooves: there's an awful lot of different kinds of moss (and lichen) and they tend to specialise in particular substrates - some might specialise in mineral rich mine spoil say: and roof tiles or asbestos sheets might already be mineral rich. There has been extensive coverage of the topic of how to get new copper coated rooves to look old, here before, and I think there are websites devoted to the topic, but I don't recall any on using copper wire - except maybe against slugs, and - with electricity - squirrels!

As a start, you could try spraying the roof with Bordeaux mixture - on a dry day so it soaks in nicely.

As with some of my other comments, I also fear that nowadays, your copper would not stay there long before it was half-inched.

S

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Harry Bloomfield saying something like:

Seems to work for those who've done it.