I'm in the process of installing solar panels on my garage roof - mainly because the house roof isn't ideal due to a loft conversion and lack of space, but also because if I bugger something up, it's the garage not the house and should hopefully be less expensive to repair...!
The garage is concrete walled (looks like prefab) with a pitched roof. Roof construction is several metal trusses bolted to the concrete (the bolts go through from the outside and are bolted to the truss on the inside). On top of these are two 75mm x 50mm (3x2in) purlins which rest on the trusses and finished off with a fibre-cement roof. Before anyone yells "asbestos!" - already had it tested, "no asbestos detected in sample".
The problem I have is the shortest hanger bolts I could get for the solar panel rails are 200mm long total, and the part that screws into the purlin is 150mm long.
The nails holding the roof are in the high part of the ridge on the tiles, with a ridge height of about 30mm.
So whatever way you cut it, driving a hanger bolt into one of those is going to blow out of the back of the purlin. Hardly ideal.
I'm thinking of screwing a length of 100x50mm timber behind each of the existing purlins, and screwing them together with Twister screws. The hanger bolts would then go through from the top, pulling everything together tight.
To get past the metal trusses I'm going to need to cut notches in the new timbers - but that will probably be the easiest part, assuming my measurements are up to snuff!
Can anyone spot any flaws in my plan?
The existing purlins are a ~5m long main length with a ~2m length at the front, both ends resting on the truss where they meet, with no mending plate. I was thinking of doing the same, but putting the shorter length at the back so I didn't create a weak point.
The other thing I'd considered (but only if it's not going to screw me over - ho hum - by weakening the roof) is to install the timbers in shorter lengths e.g. 3m each as that'll make them much easier to handle into place.
Cheers - Phil
The garage is concrete walled (looks like prefab) with a pitched roof. Roof construction is several metal trusses bolted to the concrete (the bolts go through from the outside and are bolted to the truss on the inside). On top of these are two 75mm x 50mm (3x2in) purlins which rest on the trusses and finished off with a fibre-cement roof. Before anyone yells "asbestos!" - already had it tested, "no asbestos detected in sample".
The problem I have is the shortest hanger bolts I could get for the solar panel rails are 200mm long total, and the part that screws into the purlin is 150mm long.
The nails holding the roof are in the high part of the ridge on the tiles, with a ridge height of about 30mm.
So whatever way you cut it, driving a hanger bolt into one of those is going to blow out of the back of the purlin. Hardly ideal.
I'm thinking of screwing a length of 100x50mm timber behind each of the existing purlins, and screwing them together with Twister screws. The hanger bolts would then go through from the top, pulling everything together tight.
To get past the metal trusses I'm going to need to cut notches in the new timbers - but that will probably be the easiest part, assuming my measurements are up to snuff!
Can anyone spot any flaws in my plan?
The existing purlins are a ~5m long main length with a ~2m length at the front, both ends resting on the truss where they meet, with no mending plate. I was thinking of doing the same, but putting the shorter length at the back so I didn't create a weak point.
The other thing I'd considered (but only if it's not going to screw me over - ho hum - by weakening the roof) is to install the timbers in shorter lengths e.g. 3m each as that'll make them much easier to handle into place.
Cheers - Phil
