Internal wall insulation- help!!

[paul notts]

Hi all.

I am required to do a complete rewire on a 1920s terrace property with 9" solid brick walls which is then to be replastered using 30mm wallboards dot and dabbed to the brick- that is 18mm insulation backed onto a 12mm plasterboard.

Sure many of you have done this many times so my question may have an easy answer.

Do I surface mount the cables to the brick cutting the insulation off of the board in a channel around the cables and call it clipped direct? Don't really want to be uprating cable sizes and then derating them for insulation!

Obviously there is a direct conflict between keeping the walls warm and the cables cool!

Any advice would be appreciated immensely as the reference methods in the regs do not appear to cover this situation definitively.

Many thanks in advance

 

[VoltzElectrical]

I would clip the cables to the wall and the thickness of the dab will mean you shouldn't have to cut away any of the insulation. You shouldn't need to de-rate the cables as the coolness of the brickwork and the airspace around the dabs will allow sufficient cooling.

Someone will be along shortly to disagree with me though!

 

[tazz]

Would cap it for protection, but as above can`t see any problems

 

[Andy78]

I'll disagree with you
If I was clipping direct with insulation board going over the top I would probably calculate to method 102

Someone will be along shortly to disagree with me though!

 

[tazz]

Sorry forgot abaut the 10x 2kw fires plugged in...lol

 

[Slowhand]

Run it in 20mm oval tube and butt the insulation up to the tube.

 

[telectrix]

25mm oval for 2 x 2.5mm cables in a drop.

 

[tazz]

Quicker, easier, flatter, neater......cap it side by side

 

[telectrix]

hate capping. nails either bend on hard mortar or fall out of soft. drill and plug oval tube clips for me every time.

 

[HappyHippyDad]

hate capping. nails either bend on hard mortar or fall out of soft. drill and plug oval tube clips for me every time.

Would there still be room for the boards to go over though Tel? The oval tubing is going to stick out more than capping.

 

[davesparks]

Would there still be room for the boards to go over though Tel? The oval tubing is going to stick out more than capping.

Only by a few thou, there's very little difference in them

 

[Gavin A]

How would you normally install behind dot and dabbed plasterboard?

Do that.

 

[trev]

If capping is specced on a job I always drill and plug anyway and drive the nails into the plugs. It saves a load of fannying on time.
As a rule I dont cap.

 

[7029 dave]

I like oval tube, if you have to take a bit out of the brick so be it.

 

[ferg]

Ive never come across dot and dab for insulation backed plasterboard.

Will the adhesive stick to the foil?

Electrically as above no different to any other D&D plasterboard.

 

[trev]

Ferg, not all insulated plaster board is foil backed mate. You can get stuff which has a layer of foam on the back, that's what's probably going on here.
Whether or not D&D adhesive will be any good for it is not our problem mate, that's for the boarders to sort out.

 

[ferg]

Ferg, not all insulated plaster board is foil backed mate. You can get stuff which has a layer of foam on the back, that's what's probably going on here.
Whether or not D&D adhesive will be any good for it is not our problem mate, that's for the boarders to sort out.

That makes sense.

Where I live, all external walls the plasterboard has to be foil backed.

Also d&d does'nt really exist as nearly everything is timber frame with block cladding.

 

[test electrical]

Chase the wall use 20mm conduit and plaster it into the wall and if you or really paranoid you could use galvanized.It will take twice as long but in fifty years time it will be handy to rewire

 

[Leesparkykent]

Chase the wall use 20mm conduit and plaster it into the wall and if you or really paranoid you could use galvanized.It will take twice as long but in fifty years time it will be handy to rewire

you could possibly loose the job with the cost of labour doing it this way.

 

[trev]

Chase the wall use 20mm conduit and plaster it into the wall and if you or really paranoid you could use galvanized.It will take twice as long but in fifty years time it will be handy to rewire

So despite the readily availability of things like capping and oval conduit you'd really go to the trouble of all that work?
Don't forget, in 50 years time how many of the points that you put in are still going to be in the right place for the owners of the property then? So chances are you'll have gone to all that trouble for nowt.