DIY Stable Renovation: Need Your Advice and Ideas!

sujsuj

Made some more progress on the thermal insulation side work. I’ve got enough 50mm Celotex PIR insulation boards and have started cutting them to size to fit between the slats. Since the gaps between the slats are not uniform, it’s making the job a bit more time-consuming, but progress is being made.

I installed one layer of Cromar Vent 3 Pro just inside the timber before fitting the cut Celotex sheets. I’m also planning to add another layer before installing the plywood.

My plan is to use foil tape around all the edges to improve the thermal seal and reduce any air gaps.

• Current Layer Build-Up (from outside to inside):

• (1) External timber cladding

• (2) Cromar Vent 3 Pro breathable membrane

• (3) 50 mm Celotex PIR insulation boards fitted between the framing/slats

• (4) Foil tape sealing around the insulation edges

• (5) Second layer of Cromar Vent 3 Pro (planned)

• (6) Plywood internal lining

• (7) Plywood ceiling and layer of loft insulation

Expanding form not used as I may have to readjust some of these boards for wiring.

Any other suggestions or recommendations before I close everything up? See photos attached.

WIAWSNB

How deep are the vertical timber studs? And how thick the celotex? Ie, is there an air gap betwixt them?

I just don't know if there's an issue with not having a ventilated gap there.

And not sure if another layer of membrane is needed this side of the celotex - not sure what purpose it'll serve. But, tbh, I don't know the correct sequence one should follow here.

Section62

Current Layer Build-Up (from outside to inside):
(1) External timber cladding

(2) Cromar Vent 3 Pro breathable membrane

(3) 50 mm Celotex PIR insulation boards fitted between the framing/slats

(4) Foil tape sealing around the insulation edges

(5) Second layer of Cromar Vent 3 Pro (planned)

(4) Polythene sheet - https://www.toolstation.com/pinnacle-polythene-dust-sheet/p74553

(5) Duct tape (for the joins) - https://www.toolstation.com/heavy-duty-cloth-duct-tape/p44852

(6) WBP Plywood internal lining

Using one layer of Cromar Vent 3 Pro in this situation is a waste of money. Using two layers would be bonkers. It serves zero purpose.

If the studs are deeper than the celotex is thick then use some offcuts to space the celotex away from the external timber cladding, so the inside face of the celotex is flush with studs. Cover this with polythene (easiest way to fix is stick a small 1" piece of duct tape on the polythene over a stud, then staple gun through the tape and polythene. The staple will tear through the polythene if you don't strengthen it with tape first, a 1" square of thin card works just as well)

Use duct tape to seal up the joins in the polythene, and repair any holes/rips made during fitting. The polythene forms a vapour barrier on the warm side of the insulation. It will keep any residual cold draughts outside, and stop warm moist air coming into contact with the cold timber studs and cladding. A vapour barrier is what you need, a "breathable membrane" does the exact opposite.

If you'll have an air gap because the celotex is thinner than the depth of the studs then you want the air gap to be on the cold side - (a) to give the cold wood some ventilation and (b) you don't want a cold air flow just behind the plywood lining (it defeats the purpose of using insulation).

(7) Plywood ceiling and layer of loft insulation

Make sure you put in enough noggins or battens to support the ceiling plywood - particularly around the edges of the room and joins between sheets. Preferably before you put the plywood on the walls. There would be little worse than scuffing up your new plywood walls when you need to hammer/drill into the ceiling right next to the wall.

…and have started cutting them to size to fit between the slats. Since the gaps between the slats are not uniform, it’s making the job a bit more time-consuming, but progress is being made.

This is why you laid whole sheets of celotex for the roof on top of the OSB, rather than trying to cut it to fit between the rafters/purlins. And then try to keep it in place. 🙂