Narrow Rafters - advice?

[PvNewbie]

Hi

Being newly qualified etc I did my first PV survey and notice that the rafters are rather narrow for the roof brackets that I have. The rafters are about 1 1/2 inches wide and there's no way I can use the roof hooks with them as it clearly won't meet building regs. (unless I'm wrong??)

I'm getting a structural engineer in to do the calcs for loadings etc. but I'm wondering if anyone has any suggestions as to how to widen the rafters to take the hooks, and be within regs? I could bolt timber to the sides of the rafters, but are there any rules/regs about drilling holes in rafters to add timber alongside? Also, I what size timber should I use...length/width?

I know the rules about drilling/notching joists, but not rafters.

Anyone got any suggestions? And thanks for constructive advice. I'm trying to do it properly!

Thanks

Newb

 

[topquark]

Depends on the type of roof framing. Probably the easiest thing to do would be to run a couple of noggins between the rafters then run a rafter between the noggins of the size you require. You may need to do that more than once depending on how many panels you have to fit, spacings permitting of course. It's not normally a good idea to try and sister extra timber on the side as you don't get a good fixing then as you may hit the join. See if you can find a local chippy that has experience with a cut roof if you're unsure.

 

[PvNewbie]

Thanks but that seems a bit of a faff! Especially if there's going to be a bracket every (say) 600mm. I take it installers do 'sister' the rafters with extra timber?

 

[topquark]

Probably, if you do go that route then ensure that the bit you add on is big enough to take the bracket and use builders adhesive and screws/nail gun to fit them (don't try using a hammer, coz you'll probably damage the roof).

 

[DomB]

We had exactly the same on a bungalow a little while ago and the structural engineer told us to put noggins (or trimmers?) between the rafters (we did 4"x2"). He advised we then bolted the anchor so they sat across both the noggin (trimmer?) and the existing rafter..

 

[PvNewbie]

We had exactly the same on a bungalow a little while ago and the structural engineer told us to put noggins (or trimmers?) between the rafters (we did 4"x2"). He advised we then bolted the anchor so they sat across both the noggin (trimmer?) and the existing rafter..

Thanks for that. I was thinking of using the noggin itself as a part-mount for the anchor. Are there any 'regs' for drilling through rafters for screwing in noggins? As I said, I'm aware of regs for joists, but not rafters.

 

[Worcester]

Try the Hilti GB fixing or the Azur Type 1 Roof hook, with the correct screws, (so long as the rafter can take the load) both the above are designed for UK's narrow rafters, Azur work only on slate though as no offset available. So on tile, apart from Hilti, we don;t know of any other Uk compliant product.

p.s. Having been fed up with no choice and complicated ways to comply withthe Bldg Regs, after finishing off all the BRE testing we are launching our own UK compliant universal roof hook later this year!

 

[PvNewbie]

Thanks Worcester.....what makes the Hilti better? Are the offset for the mounting holes less far apart? (as in more central to the rafter)

 

[edexlab]

Try the Hilti GB fixing or the Azur Type 1 Roof hook, with the correct screws, (so long as the rafter can take the load) both the above are designed for UK's narrow rafters, Azur work only on slate though as no offset available. So on tile, apart from Hilti, we don;t know of any other Uk compliant product.

p.s. Having been fed up with no choice and complicated ways to comply withthe Bldg Regs, after finishing off all the BRE testing we are launching our own UK compliant universal roof hook later this year!

Good luck with the roof hook ,when you say universal ,will it also be height adjustable?

 

[Worcester]

will it also be height adjustable?

Experience and long discussions with lots of other installers, says that we'll have only one fixed one at 45mm plus available spacers, (some installers ONLY use that one hook) plus an adjustable one.

If any one wants to add to that, we'd be glad to hear, either openly here, or pm me.

 

[Worcester]

Thanks Worcester.....what makes the Hilti better? Are the offset for the mounting holes less far apart? (as in more central to the rafter)

Yes they are, they are much more 'inline', they also take 3 x 6mm coach screws and are just offset to avoid having 3 screws in a line and splitting the timber.

Down side is cost and minimum order quantity (MOQ) , even at maximum discount. (Silly things in the Hilti system, like MOQ for rail butt joints is 30 items at £4.50+ each )