Refurbing/insulation for loft room

benson1980

Hi all, 

We have a loft room (not habitable) in our detached house which needs a total refurb. The plasterboard appears to have had lining paper applied which has been painted. Veluxes need to be replaced etc. Behind the plasterboard there is some plastic sheeting (presumably some form of vapour barrier?) and behind this some compressed wool-type insulation.

There is a patch of damp that you can see in the top right hand corner. I'm not entirely sure how the gable end wall has been prepped but this part of it is rather messy and has mould patches which I believe are from condensation rather than ingress from outside.



What would people recommend in terms of re-doing this room? We have an open loft hatch with loft stairs leading up to this area so it needs to be well insulated, and it's a useful room as the kids use it a lot. I was going to tear down all of the existing plasterboard and get it re-boarded and skimmed. Would it be best just to strip the whole lot out, and for this room use rigid insulation, then reboard? What should I be doing with the gable end wall, and are vapour barriers the way to go/do we need to consider ventilated cavity etc?

Appreciate any advice. Thanks

grumbler

IIRC, for new conversions it's 100mm of rockwool insulation between the rafters plus 100mm of hard insulation (Celotex/Kingspan) under the rafters. If the gable wall has a cavity, it has to be filled with insulation. Otherwise some extra insulation is needed.

FreeBear

grumbler said: IIRC, for new conversions it's 100mm of rockwool insulation between the rafters plus 100mm of hard insulation (Celotex/Kingspan) under the rafters. If the gable wall has a cavity, it has to be filled with insulation. Otherwise some extra insulation is needed.

The requirements for a refurbishment is usually lower than for new conversions/builds. Certainly, the roof needs quite a bit of insulation - 150mm of Celotex springs to mind. But a gap must be left under the tiles (and any felt) to allow for ventilation.

On the gable wall, 50mm of Celotex would be a minimum if it is a cavity wall. For a single skin brick, 100mm, and for double thickness solid brick, 75mm. Tape the joints between each sheet of insulation board (Toolstation do an aluminium foil tape), and optionally use a vapour control membrane.

Getting full 8x4 sheets up through a loft hatch is going to be <ahem> entertaining, so you may well need to cut the materials to size outside - A sharp serrated kitchen knife is an ideal tool for cutting Celotex type boards. Less mess than a hand saw, and a cleaner cut too.

Bendy_House

Hi Benson.

A close up pic of that damp patch would help determine whether it's cond or ingress.

Are you intending to strip the walls anyway? If so, that would be ideal so you can check what's behind it.

In essence, you need to allow the roof rafters and other timber to be well ventilated to the outside, usually via gaps or grills along the eaves and soffits. Nothing should be added that will reduce that.

Then look at the inner envelope - the actual room. Do you wish to get it up to current building reg standards, or just make it comfy and pretty efficient? The difference is 'thickness' of walls and ceilings, and, to a degree, cost.

Depending on what you have visible once the p'board has been removed - ie, timber studs with a loft void behind it, or perhaps just the actual roof rafters with only the depth of these timbers to play with - then you either board the room side of it with, ideally, Celotex-type rigid insulation and then p'board that, or ( if there's a nice void) you can fit the Celo snuggly in between the timbers, leaving it flush with the front edges, and then overboard with a thinner layer the whole inside, before p'board as before. The latter will gain you a couple or more extra inches room size.

Or, use ThermLamBoard, which is p'board with insulation already bonded to it - slightly quicker.

I'd want to investigate that damp spot, tho' - if that's it visible in the far right top corner, it looks too well defined to be condensation. And cond damp/mould would also tend to be RIGHT in the corners where's there's little air flow.

benson1980

Thanks all for the advice.

Here's a photo of where the damp forms. It did look odd, for condensation- I actually had a roofer round to have a look whilst he was replacing a ridge tile for me and he said there's nothing wrong with the roof and it was probably condensation. 



I am looking to essentially strip and refurb the entire room so will investigate further. Plan is definitely just to make the room more comfy. There is currently compressed rockwool or similar behind the board.

Bendy_House

The damp right in the corner could be cond, but if that's a damp vertical strip in front of the shelf, then I think that can only be from either a 'leak', or else there's something REALLY cold behind it!

Anyhoo, you'll hopefully soon know.

If the sloping ceilings have been boarded directly to the rafters, then you'll need to ensure it has a good 50mm vent gap along the roof underside, along the top ridge, and down the other side. If the rafters are at least 1000mm, then a good insulation level could be achieved by fitting 50mm Celo snuggly in between, any gaps filled with exp foam, and then ideally the whole over-boarded with even 25mm Celo, and then p'board.

That will be cosy. Anything more than this will provide diminishing returns, and a greater loss of internal space.

If cost is a big factor, then Jablite (expanded foam insulation) in between the joists and  25mm Celo over would still be good, and very effective. As it's 'beady' and messier/less neat to cut, take greater care to fill any gaps with a carefully extruded bead of exp foam.

FreeBear

Bendy_House said:  If cost is a big factor, then Jablite (expanded foam insulation) in between the joists and  25mm Celo over would still be good, and very effective. As it's 'beady' and messier/less neat to cut, take greater care to fill any gaps with a carefully extruded bead of exp foam.

There isn't a huge difference in cost between PIR/PUR (Celotex) insulation and EPS/XPS(Jablite). Celotex (other brands available) has a better insulation performance with the added bonus that the aluminium facing acts as a vapour control membrane as well as reflecting a small amount of heat back in to the room.

Bendy_House

Thanks, FB - a no-brainer, then.

Apodemus

Bendy_House said:

If cost is a big factor...

Well, this being MSE...

I'd suggest that if cost really is a big factor, then the OP should be asking whether a full refurb, including replacing a velux window and completely stripping out all the linings and insulation, in a "non-habitable" room, really is the best option!

Access by means of a loft-hatch and loft stairs is probably never going to meet building regs, so there seems little reason to re-build everything else to current building regs standards.

I'd just get that leak investigated, encourage the kids to open the window more often to help with the condensation and then let the kids give it a lick of paint in their choice of colours and designs!  Trust me, the kids will never appreciate the difference between that and a full refurb!

benson1980

Apodemus said:

Bendy_House said:

If cost is a big factor...

Well, this being MSE...

I'd suggest that if cost really is a big factor, then the OP should be asking whether a full refurb, including replacing a velux window and completely stripping out all the linings and insulation, in a "non-habitable" room, really is the best option!

Access by means of a loft-hatch and loft stairs is probably never going to meet building regs, so there seems little reason to re-build everything else to current building regs standards.

I'd just get that leak investigated, encourage the kids to open the window more often to help with the condensation and then let the kids give it a lick of paint in their choice of colours and designs!  Trust me, the kids will never appreciate the difference between that and a full refurb!

Yes good points. The loft arrangement is in fact a massively oversized open hatch, with a permanent set of paddle steps up to it. Therefore it’s not only the comfort in the room but heat loss for the whole house.  

That said, I think the potential option of simply leaving what’s there in terms of insulation (after investigating that damp patch) then overboarding with insulated plasterboard might be the best option.

Kids choosing decor- I think that's what the previous owner did and why I'm left with a load of red skirting and window surrounds

Apodemus

I would suspect that your open hatch is the main source of the humidity that is giving rise to the condensation.  Is there an option to close the hatch when the room is not in use?  The alternative might be to leave the vent on the Velux in the open position, but that will mean a greater loss of heat from the house.