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Insulation

Insulating a boarded loft which has no joist insulation

Anonymous user 03/03/2024 - 3.27 PM

So i've read conflicting reports online and i need some help! Our loft space is floorboarded with tongue and groove boards but underneath the boards, there’s no insulation between the joists. I’ve had some differing conversations regarding how to insulate and i need help in choosing the best option. It’s a time consuming and bigish job for me to remove the boards and insulate between joists as normal and our joists have the issue of only being about 100mm deep which apparently makes insulation between them more challenging. Option two is to just insulate over the boards and be done with it but i’m concerned condensation could be a factor – i don’t mind it being less efficient than if it were installed between the joists. I’d love to get a clear and honest idea of what needs to be done seen as I have 6 rolls of the stuff ready to be put down but i don't want to cause any more issues with damp.

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5 Answers

Advanced eco ltd

Rating: 5 out of 5

Haverhill

There is no issue with insulating over the boards at all, just as the above say you will loose space.

Answered15 January 2020

JA Carpentry

Rating: 5 out of 5

Brighton

I would say insulating under the boards would have better results, as far as condensation, i can’t see it being a problem with going over the top, however you would lose the space.

Answered12 January 2020

Brothers construction

Rating: 5 out of 5

Halstead

You would definitely be better off insulating Under the boards, regulation nowadays is to have 270mm of insulation in a loft space. 100mm between rafters and then 170mm over the top. This will provide the best results having said that going over the top would be fine also but maybe put loft legs on the boards already there and create a new storage area. Condensation shouldn’t be a problem as there is normally adequate airflow in loft spaces

Answered22 January 2020

Anonymous user

I would say insulate over the boards, you need 300mm of insulation for you to to get the required effect, the only down side is you will lose the space, but saying that you could make a raised platform for storage.

Answered12 January 2020

Extract Insulation Ltd

Rating: 5 out of 5

Gosport

You will get condensation problems and/ or ghosting on the ceiling in the rooms below. You will probably be able to see you joists in a few years. Why not look at blown cellulose and core holes in the board and blow it in depending on if you have down lights?

Answered23 September 2020