Order of play

[jpadie]

Dear hive mind

 

I'm building a garden office with shower room and loo.  The timber frame is up, the subfloor insulated and closed, the roof on.  The frame is clad externally in osb3 and tyvec.  The sliding doors will go in on 16/11.

 

To dos include insulating the walls and roof, building the internal partition for the wet room, electrics, plumbing, ashp (arriving this week), plasterboard, decor and flooring.  

 

I'm planning to run electrics down the external wall under the cladding and across the top of the roof rafters.  There should be enough depth for regs.  

 

Am I right in thinking that I should put the insulation in the walls and roof space, and install the vapour barrier before pulling cables for first fix electrics?  Ditto plumbing (wall penetration already done for the waste pipe and connection to soil stack and sewer lines is in place, but I've not plumbed the water lines yet.   I'm also thinking I could plumb the water ingress now.  

 

Insulation is PIR but I wonder whether the areas around the pipe penetrations should be rockwool to avoid too much cut out.   Alternative is cut out and then fill with expanding foam.

 

Basically I'd appreciate a little guidance on the best order for the remaining tasks!

 

Last q is on plasterboard:  the timber frame is a little wavy in the sense of there being valleys and hills in the joists. And sometimes the edges at the rim joists are perhaps creating a 3mm lip.   How much play can plasterboard absorb?  Should I plane down all the proud areas?  

 

Thanks in advance!

 

Justin

[Mr Punter]

I don't think you are supposed to run cables in the external cavities.  Check with the sparky who is doing the sign off.

 

Foam or rockwool is fine around pipe holes.

 

Plasterboard is fairly forgiving.  You could add some thin hardboard to low spots.

[JohnMo]

4 hours ago, jpadie said:

Basically I'd appreciate a little guidance on the best order for the remaining tasks!

Order really depends on if you have a service void between vapour barrier and plasterboard. The above sounds like you don't.

 

Assume as you have plumbing, toilets etc you are subject to building regs as a minimum.

 

I would concider mineral wool instead of PIR for between timber, much easier to install, something like Frametherm 32.

 

Did all my wiring behind the vapour barrier on and through the studs. Then just brought the cables through barrier where needed and sealed up. I made the external membrane airtight, with limited penetrations in that and taped to the DPM.

 

Not sure I would do external wiring, does who ever is signing off, agree with that?

 

 

[jpadie]

Thanks both

 

Have written to building control about sign off on the sparks.  No reply yet.  So far as I interpret the regulations for electrical wiring, under the cladding on the external side of walls is fine providing it is in one of the safe zones.   The safe zone in question is 50mm depth. 

 

I'm not planning a service void but that may be a good solution for one particularly 'busy' wall.