I'm about to start fitting an additional 40mm celotex layer on the inside of our timber frame.  The current plan is to fix with 25mm battens over the top into the frame studs, then to board onto the battens to leave a service cavity.  I'm guessing that if the professionals did this, it would be a nail gun job, but as I don't have one, any problems with fixing with 100mm screws?  Also, this will mean screwing through the airtightness membrane; I'm assuming the compression will avoid leakiness?

I fitted 50mm over my studs, and used screws. Big advantage over nails is that you can feel it bite into the stud.

I initially fitted a few screws per board, using insulation washers (£12/100 from Amazon), which held the boards securely until I could put the battens on.

A screw through the air tight layer is okay. If by chance it misses the stud, do bot remove it, leave it there filling the hole and just fit another one.

 

Pre drill the studs at 450mm and 1150mm above finished floor level to allow for cables, or leave small gaps in the studs at that height.
 

Thanks guys. 

Dave - not sure I understand the pre-drilled studs tip; is that for if the studs are fixed horizontally rather than vertically?

Edited March 2, 20179 yr by Roundtuit
typo

I am assuming the battens will run vertically fixed to the timber studs.

 

You (or your electrician) might want to do some of the wiring by going horizontally from socket to socket for instance, which will be in a safe zone for wiring. So it's a lot easier to preempt that and drill a horizontal hole through the battens at switch and socket height before you fix them to the wall.
 

Ah, thanks.  Yes, battens will run vertically.  I didn't realise it was acceptable to run wiring horizontally, but it is being done by a proper sparky so I'll check with them.

Yes, it's all about "safe zones". Once you have fixed an accessory to the wall, you can run cables horizontally or vertically from it, but NOT at an angle.  It's quite common with a TF house with a service void to just run cables around the room at socket height *. It's a lot less common to do the same with a light switch as that normally goes up, but there are plenty of cases where running a light feed horizontally from one switch to the next is a good idea.

 

 

* I had a big argument with the joiner on a job last year. He was trying to tell me I must run socket cables up the wall, along above the ceiling, then back down to the next socket.  I had to educate him about safe zones including NEVER put screws through the plasterboard at the same height as sockets because there might well be wires there. That was the gist of his argument that if I ran them horizontally he might put a screw through them.   It still bugs me that no other building trades seem to have heard about the concept of safe zones for wiring.
 

15 hours ago, ProDave said:

A screw through the air tight layer is okay. If by chance it misses the stud, do bot remove it, leave it there filling the hole and just fit another one.

 

Pre drill the studs at 450mm and 1150mm above finished floor level to allow for cables, or leave small gaps in the studs at that height.
 

 

Did you mean to say batten, rather than stud?

1 hour ago, Crofter said:

 

Did you mean to say batten, rather than stud?

He's screwing through the battens, through the insulation and into the stud of the timber frame. So if he's got his measurements wring and the screw does not go into the stud, leave it in place and try again.
 

@ProDave Yes got that bit- I meant about leaving gaps for wiring,. Presumably no point in having gaps in the studs, but you do want holes or gaps in the battens? Just asking because this is what I'm doing this morning!

Yes sorry, holes or gaps for wiring in the battens that create the service void, sorry for the confusion.
 

I was going to run my service cavity batons horizontally at 400 mm centres and 45mm baton.  Would this be an issue as my studs are not at 400mm or 600mm centres.  I would need to put in noggins to make the correct centres in areas.

 

Would this be an issue?  It would also let the electrician run cables easier around the sockets

 

thanks