Converting outbuilding into bathroom

[FifiGo]

Hi all, we are planning on converting a single brick skin outbuilding into a downstairs bathroom with access via a newly installed door in the kitchen.

The outhouse is big enough to create a completely separate internal stud wall with 100mm kingspan (or similar) so that we can allow the external bricks to breathe.

The roof is pitched and tiled with rafters exposed. We plan to create a lowered ceiling again with 100mm insulation, leaving the roof void above to breathe and hopefully prevent condensation etc.

The original door will be bricked up and the window size reduced and replaced with a triple glazed unit.

Floor will be insulated as it's currently lower than the house floor level so this will level it out and hopefully stop the cold.

Is it likely this combination of works would be approved by building control?

Our local BC department aren't willing to give you an opinion on whether chocolate would melt in a hot oven unless you pay for the privilege of asking a question!

Thanks for any input.

 

[Murdochcat]

Pay their fees. You’ll need them involved

 

[noseall]

Hi all, we are planning on converting a single brick skin outbuilding into a downstairs bathroom with access via a newly installed door in the kitchen.

The outhouse is big enough to create a completely separate internal stud wall with 100mm kingspan (or similar) so that we can allow the external bricks to breathe.

The roof is pitched and tiled with rafters exposed. We plan to create a lowered ceiling again with 100mm insulation, leaving the roof void above to breathe and hopefully prevent condensation etc.

The original door will be bricked up and the window size reduced and replaced with a triple glazed unit.

Floor will be insulated as it's currently lower than the house floor level so this will level it out and hopefully stop the cold.

Is it likely this combination of works would be approved by building control?

Our local BC department aren't willing to give you an opinion on whether chocolate would melt in a hot oven unless you pay for the privilege of asking a question!

Thanks for any input.

All looks good, but a bit on the lean side. You are probably looking at between 120 - 150mm of Celotex on half brick thick structures, with the concentration of insulation rising from the floor upwards.

As thick as you can get it (PIR) on the floor.
100mm (PIR) between studs and say 50mm across the studs for the walls.
300mm + glass-wool type insulation laid on top of the ceiling joists.

Are you having the renovation designed or just winging it?

 

[FifiGo]

We will involve them but we just want to get some idea if what we're thinking is feasible and meets current regs.

 

[FifiGo]

All looks good, but a bit on the lean side. You are probably looking at between 120 - 150mm of Celotex on half brick thick structures, with the concentration of insulation rising from the floor upwards.

As thick as you can get it (PIR) on the floor.
100mm (PIR) between studs and say 50mm across the studs for the walls.
300mm + glass-wool type insulation laid on top of the ceiling joists.

Are you having the renovation designed or just winging it?

Thanks noseall, that's really helpful .

There will be a small element of birds flying .

 

[FifiGo]

All looks good, but a bit on the lean side. You are probably looking at between 120 - 150mm of Celotex on half brick thick structures, with the concentration of insulation rising from the floor upwards.

As thick as you can get it (PIR) on the floor.
100mm (PIR) between studs and say 50mm across the studs for the walls.
300mm + glass-wool type insulation laid on top of the ceiling joists.

Are you having the renovation designed or just winging it?

Noseall, what would you consider a good enough gap between the brick wall and new stud wall?

 

[noseall]

Noseall, what would you consider a good enough gap between the brick wall and new stud wall?

There need be no gap. You could trap (1200g) membrane directly against the wall, with the 100mm sheets of Celotex and a 50mm stud wall built hard against the sheets. Fill the voids in the stud wall with 50mm Celotex. Foil tape all the Celotex layers. Use duplex plasterboards.

 

[noseall]

Noseall, what would you consider a good enough gap between the brick wall and new stud wall?

The membrane should be lapped onto the floor and possibly the ceiling, depending how you intend VCL-ing.

trap.jpg

• noseall
• 26 May 2024

 

[FifiGo]

Thank you so much Noseall. That's really helped such a lot!
That should satisfy Mr BC Man - even the one we have to deal with!

 

[^woody^]

Building control are inspectors not advisors, and it can really get their back up when applicants or worse still builders keep asking them how to do stuff.

There are lots of ways to conform to building regulations - some good, some bad, some cheap, some expensive.

Best to have a clear specification drawn up and get comparable quotes on that, not on what builders think or want to do.

If self building, think of what you want to acheive and how much you want to spend, and then research the options of achieving it.

For the wall, read the many garage conversions threads. No air gap is required or desirable, but you need to detail the damp membrane properly.

 

[Mrs_Bean]

Hi @FifiGo I landed here as we have just this minute been discussing whether this is even possible. So I’m VERY interested in your project. Do you mind sharing how much you are estimating the project to cost? Thanks!