Corrugated garage roof - any suggestions

[BTC]

I'm really looking for any suggestions from those in the know.

I have an Onduline garage roof (corrugated compressed bitumen and fibre sheets) that is leaking and sagging causing water to pool. It's at approximately 7-ish degrees pitch. As a side problem there is insufficient overhang to carry rainwater into the gutters, which is causing problems with the brick walls.

Looking at the structure the joists/rafters look too far apart (indeed I think it should be decked for such a low pitch) and it looks like there are insufficient battens for such a roof - this seems to be the source of the sagging problem.

For budget reasons I'd rather not go down the road of professional re-roofing or anything that needs building control approval. I'm also concerned that anything that requires a lot more timber on the roof will both be beyond my skills and also the strength of the existing roof timbers (which are forty years old and are well below the current building regs for roofs).

So, anyone got any suggestions? I'd be up for re-sheeting the roof, but that could just have exactly the same problem regarding sagging. If I decked with ply underneath new sheets, I'm concerned that the load would be too much for the roof.

 

[masona]

For budget reasons I'd rather not go down the road of professional re-roofing or anything that needs building control approval.

Generally speaking the building regs on garages roof are 3m high for flat roof and 4m high for pitch roof, so no problem there.

So, anyone got any suggestions? I'd be up for re-sheeting the roof, but that could just have exactly the same problem regarding sagging. If I decked with ply underneath new sheets, I'm concerned that the load would be too much for the roof.

Really need to see a photo of the roof structure if possible

 

[BTC]

Thanks for the post mate, I'll try to get a photo taken.

However to give you an idea of the frame it's 38 x 75 mm joists, maximum span 4.58 m. The spacing is pretty random from 910mm to 1600mm. A single up and over garage door is also suspended from some of them adding to the load.

I've just found out that Onduline do eaves trays that should cure the overhang/gutter problem, so I've just got the sagging to sort out.

 

[BTC]

Still haven't managed to get a photo. Son has destroyed our camera and we haven't got a replacement yet.

 

[foxhole]

I found the bitumen roofing you have to become water logged and sag, only thing that worked for me was to remove and sheet the roof with timber [osb board]before replacing bitumen, it needs far more support than just rafters, no matter how close they are.