loft insulation

[Halo Jones]

That is not a dwarf wall: a dwarf wall is made of brick.. That’s why you confused me, that “wall” as you call it lateral bracing.

Posh concrete tile: ok warning here, that may be an asbestos based tile, you will only know definitively by testing (unless they have a visible maker’s reference on the underside that you can research) so worse case you do not want to be breaking or cutting any of the tiles.

Yes ventilation is best, but vents on the gable may not necessarily the most efficient solution & you may have had other influences, which is why I asked.

Ok so the point of your exercise is to make a dry storage area,

My suggestion would be, leave the membrane for now, (it was put there for a reason; it may be the main waterproofing as sarking felt may not good for that on its own), and put down your horizontal insulation & get the ventilation roof vents installed & see if that solves your problem.

You mentioned boarding the bracing: if you don’t need to do this, then don’t, as its additional loads that can block the flow of air & negate the point of ventilation.

The best combination of ventilation is a ridge & eaves, but installing the ridge vents could break tiles, which as there is an asbestos risk I would avoid.

If you can’t go for a ridge vent you can get a tile vent (best installed at the top of the roof peak on both sides)
Lastly would be some form of gable vent: this means forming an opening in the brickwork, which can be messy & then install a vent brick

The vent tiles are available in lots of styles so you should get one to match existing.

I hope that helps, I am not a building surveyor but that should be somewhere to start.

[FiveTimes]

Hey HJ some advice please.... my property is on 3 floors with the top floor being a playroom + extra bedroom & it was built like this so not a conversion. The dwarf walls run both sides of the loft and are timber stud & uninsulated plasterboard, the roof void has insulation beneath the roof covered by a membrane - and some insulation on the floor joists - there is no ventilation in this void & I believe this makes it classed as a "warm space"

What happens is warm air condenses on the membrane and drips down onto the floor joists insulation, so I would like to remove all the insulation from under the roof, top up the floor joists to 270mm, insulate the plasterboard dwarf walls and install ventilation in the soffits and gable walls to turn this void into a "cold space"

If I remove the membrane which is a bit tatty and ripped (it has mineral wool between it & the tiles) do I have to replace it with anything or can I just leave the underneath of the roof tiles open?

I think you need a good flow of air to stop the condensation.

A couple of roof vents and some vents in the sofits but the insulation between the rafters needs a small space between roof and insulation to allow air flow.

[Troll]

That is not a dwarf wall: a dwarf wall is made of brick.. That’s why you confused me, that “wall” as you call it lateral bracing.

Posh concrete tile: ok warning here, that may be an asbestos based tile, you will only know definitively by testing (unless they have a visible maker’s reference on the underside that you can research) so worse case you do not want to be breaking or cutting any of the tiles.

Yes ventilation is best, but vents on the gable may not necessarily the most efficient solution & you may have had other influences, which is why I asked.

Ok so the point of your exercise is to make a dry storage area,

My suggestion would be, leave the membrane for now, (it was put there for a reason; it may be the main waterproofing as sarking felt may not good for that on its own), and put down your horizontal insulation & get the ventilation roof vents installed & see if that solves your problem.

You mentioned boarding the bracing: if you don’t need to do this, then don’t, as its additional loads that can block the flow of air & negate the point of ventilation.

The best combination of ventilation is a ridge & eaves, but installing the ridge vents could break tiles, which as there is an asbestos risk I would avoid.

If you can’t go for a ridge vent you can get a tile vent (best installed at the top of the roof peak on both sides)
Lastly would be some form of gable vent: this means forming an opening in the brickwork, which can be messy & then install a vent brick

The vent tiles are available in lots of styles so you should get one to match existing.

I hope that helps, I am not a building surveyor but that should be somewhere to start.

That is not a dwarf wall: a dwarf wall is made of brick.. That’s why you confused me, that “wall” as you call it lateral bracing. Miss picky... search "loft conversion & dwarf walls" to see how much it is in common useage!

Posh concrete tile: ok warning here, that may be an asbestos based tile, you will only know definitively by testing (unless they have a visible maker’s reference on the underside that you can research) so worse case you do not want to be breaking or cutting any of the tiles. OK - I've replaced a few over the years so pretty sure they have no asbestos but thanks for the heads up

The best combination of ventilation is a ridge & eaves, but installing the ridge vents could break tiles, which as there is an asbestos risk I would avoid. - Was thinking more along lines of vented soffits which are easyish to install

If you can’t go for a ridge vent you can get a tile vent (best installed at the top of the roof peak on both sides)
Lastly would be some form of gable vent: this means forming an opening in the brickwork, which can be messy & then install a vent brick

Already put gable vents in (one brick size) into both voids - front & back

I hope that helps, I am not a building surveyor but that should be somewhere to start.
Thanks...

[lilelvis2000]

Me so confused. I' sure I typed in contractoruk.com but somehow I've ended up at B&Q forums. Though the avatars and names seem familiar.

[Halo Jones]

Miss picky... search "loft conversion & dwarf walls" to see how much it is in common useage! only by common people

Was thinking more along lines of vented soffits which are easyish to install The soffit is located in the eaves: we are talking about the same thing

Already put gable vents in (one brick size) into both voids - front & back a single brick front & back will not give you enough flow through on their own.