Loft room plasterboarding

[drives]

Hello all,

Could do with some advice.

I need to board my loft room as per photo. I have 27mm insulated tapered edge plasterboard (spec stated the foam backing acts as a vapour barrier so think that side of things is ok) to fix to the rafters and over the eaves. There are some noggins in place at the top and bottom of the sloped sections.

A couple of questions spring to mind:
I was going to tape and joint so need to keep the board widths as is. Do I need to install additional noggins to secure the vertical edges of the board? Or can I just secure it to the nearest rafter.
Where the boards are meeting on the different planes, is there a trick to doing this? They obviously won't neatly butt up against each other, is all I was thinking...

 

[noseall]

Do I need to install additional noggins to secure the vertical edges of the board

Yes.
Short joints should be staggered (bonded) too. So one noggin may not be any use or in line with the next run of boards because of the staggered bond.

 

[drives]

Thanks for the above advice.

Just to follow up on this- would people advise removing all of the rockwool type insulation and installing rigid board with the air gap behind?

I'm a bit torn what to do, firstly because of time and cost, but also it has been like this for decades (loft room 'converted' by previous owner), and presumably been ok. I've also got similar insulation installed between exterior studs in our dormer, packed in tight with no vapour barrier, which has also held up fine. Albeit perhaps the principles of this insulation between rafters is slightly different, being directly underneath the roof?

 

[^woody^]

You would board with the longest edges horizontally, and those edges don't need noggins unless at the apex and eaves edges. All the short edges of the board should meet at and be fixed on the rafters. You need noggin/support for the ceiling boards where the ceiling meets the stud walls.

 

[drives]

You would board with the longest edges horizontally, and those edges don't need noggins unless at the apex and eaves edges. All the short edges of the board should meet at and be fixed on the rafters. You need noggin/support for the ceiling boards where the ceiling meets the stud walls.

I thought I'd need to do it the other way as the angled rafter section is around 1.4m- therefore if I board with the longest edge horizontally I'd be left with two non tapered edges that I couldn't tape and join properly?

I do have noggins in place at the apex and eaves edges already- would this be enough just to secure the long edge at either end?

 

[^woody^]

Always board perpendicular to any joists/studs, be it ceilings, walls, floors or roofs and half bond the boards as this then minimises the risk of plaster cracking or makes a stronger bond of the floor/wall/roof/ceiling.

The tapered edges are more for when taping and joint filling and not skimming. Mesh joint tape will be fine.

 

[drives]

Always board perpendicular to any joists/studs, be it ceilings, walls, floors or roofs and half bond the boards as this then minimises the risk of plaster cracking or makes a stronger bond of the floor/wall/roof/ceiling.

The tapered edges are more for when taping and joint filling and not skimming. Mesh joint tape will be fine.

ok thanks. My plan was to tape and joint rather than skim, hence why I couldn't see how I could make it work if I installed them perpendicular.

 

[^woody^]

Well even when taping and filling, you may always get situations where boards are butted together along a run or at corners, where the wedges are not tapered.

But do what works best, minimise cutting, and just be mindful of the principles.

 

[drives]

Well even when taping and filling, you may always get situations where boards are butted together along a run or at corners, where the wedges are not tapered.

But do what works best, minimise cutting, and just be mindful of the principles.

Will do thanks for everyone’s help.

I’ve also ordered some celotex this morning and will remove all of the old wool type insulation - so I can leave the air gap behind as appears to be recommended.

 

[^woody^]

An air gap above Celotex does require vents at the eaves and the ridge, ortherwise it wont do much.

The insulation should be between and below the rafters, otherwise you will get lines on the ceiling where the cold rafters and noggins are.

Take care with the vapour check layer to stop air or moisture getting into the roof. Use foil tape to tape all joints.

Is this being done under building control? Do they need to see the insulation and approve it?

 

[drives]

An air gap above Celotex does require vents at the eaves and the ridge, ortherwise it wont do much.

The insulation should be between and below the rafters, otherwise you will get lines on the ceiling where the cold rafters and noggins are.

Take care with the vapour check layer to stop air or moisture getting into the roof. Use foil tape to tape all joints.

Is this being done under building control? Do they need to see the insulation and approve it?

Ok thanks. There is some air flow within the eaves space as the roof line doesn't follow those rafters; there's a dormer on the first floor and there are vents all along this, so that should help.

I will tape all the joints and plus the insulated plasterboard I'm putting on top stated that the foam is in effect a vapour barrier so should be good there.

No consultation with building control as there's no way it would meet regs. It is what it is really...half the loft space was converted by the previous owners but not done particularly well. There was a leak by the chimney stack so I had to rip out large chunks of the plasterboard that was in situ anyway. The roof/chimney now all been professionally repaired/rebuilt, and new veluxes installed. Just trying to get it to a reasonable spec so the kids can use it again as a bit of a play area. It's a handy space to have.