Drilling holes?

[dokkan1080]

Can these be drilled?

The diagonal beams going up to the roof that is?

 

[dokkan1080]

can you not run cables along the top of the wall, on that horizontal timber, then clip up side of rafters?

That was the plan, but now its all changed :/

I'm getting the idea that drilling them is not a good idea, that and if the ring goes up and over the roof it needs to be de rated if its in the Insulation...

 

[Mike Johnson]

Putting the cable over the rafters will put it on the underside of the breathable membrane so technically not in the insulation which I assume is going between the rafters.

 

[Zerax]

IMHO... I'd be asking for a drawing/specification of how they propose to install the insulation and ceiling finish. I suspect that it'll be celotex type board with and air gap between it and the breathable membrane... this would sit flush with the face of those rafters... this would then all be over-sheeted with more celotex to bring it up to the required u value and providing the vapour barrier. Then over this would be the pasterboard.

Or maybe they intend to use the foil blanket type insulation over the whole ceiling ?

Also... what are the cables for ? lighting ? led tape ? led panels ?

Once you know what the plan is.. you can then work out your cabling plan... At this stage of proceedings... I would not be thinking about drilling anything.

 

[Mike Johnson]

Yes get hold of the Bill of Quantities and the Architects specification or just do the job you quoted for without over thinking it.

 

[Intoelectrics]

What is the span of them, dimensions between walls and rake of rafter, because they look undersize to me.

You can't really tell that from the picture

 

[Intoelectrics]

The rafters look as though they have been compressed at the point of contact with the wall plate, I don't understand that junction?

Looks to me like a common junction where the timber rafter has a "birds beak" cut out to sit on the wall plate with an over hang to carry the facia and soffits

 

[Mike Johnson]

There does not look like a birds mouth to me as the rafter is undersize by the look of it, if it had been birds mouthed the timber beyond would be undersize to take a soffit and facia board, so little you can tell from the photograph, but as I said above just get on and do the job you where paid for without drilling the rafter, agree with client to feed the cable over the top of the rafter under the breathable membrane, get paid walk away the rest is not your problem.

 

[Zerax]

It might only be a garage or something ?

 

[Mike Johnson]

What difference does that make?

 

[Zerax]

What difference does that make?

The span ? roof loading ? double pitched ?

 

[Mike Johnson]

The structural needs don't change, the span is what it is, the roof loading is the same, whether it's double pitched as a house or a garage makes no difference.

 

[Zerax]

The structural needs don't change, the span is what it is, the roof loading is the same, whether it's double pitched as a house or a garage makes no difference.

A house span can be 5m vs a garage of 2m, garage roof can be felt shingles vs. a house of concrete tiles... etc etc..... so you need to know more about the roof before you can say if it's rafters are over or under sized. I could build you a perfectly sound roof out of a matchstick... but it won't support much !!

 

[DPG]

A house span can be 5m vs a garage of 2m, garage roof can be felt shingles vs. a house of concrete tiles... etc etc..... so you need to know more about the roof before you can say if it's rafters are over or under sized. I could build you a perfectly sound roof out of a matchstick... but it won't support much !!

Oooh I've got the popcorn ready now.

 

[pirate]

Until we know what the structure is, and its design, we cannot make any fully informed decisions as to whether it is ok to drill the timbers, or not. We may, given years of experience, make a decision with which we are confident.
It is well-known that in most new-build houses, for example, the roof trusses are deigned down to a size that will support the designed roof, but no more. Hence, the NHBC new homes handbook strongly advised against storing stuff in the attic, and certainly said not to floor it, because the trusses wouldn't adequately support the weight.
In the OPs case, if it's clear that a hole in the timber is insignificant, that's one scenario...but we need to know the roof design and purpose before making holes in it.
A major housebuilder was constructing new homes near me a few years ago. They had a bungalow design, and a similar one where there were 2 extra bedrooms and a bathroom in the loft. The difference in price was over £100k. Why not buy the cheaper one, then add the extra rooms later? Because the roof trusses were too small to support the extra load. I asked a structural engineer to quote me for the bigger trusses...the cost of installing the larger trusses was £800...so, still a bit left over for some plasterboard, doors and a bathroom suite.
Decide how big the holes have to be...for lighting circuits, very small...will those holes compromise the integrity of the roof structure? Just make sure you can justify your calculations.

 

[telectrix]

Hence, the NHBC new homes handbook strongly advised against storing stuff in the attic,

buggers would have a heart attack if they saw in our attic. there must be well over a ton stacked in there. Still built in 1956 when they used real wood, purlins and rafters, not these stupid trusses that make it well nigh impossible to move in the attic.