Boarding over loft insulation can be DIY’d – it isn’t complicated but it will be physically hard work. It is recommended that you have at least 270mm of loft insulation but going for bit more can be convenient.
Boarding over loft insulation – add more joists at right angles to the existing ones then roll out additional layer of insulation inbetween
We used 100mm thick sheeps’ wool insulation in a space covering 55m2. The original 200mm layer of mineral wool was left in place. 100mm x 47mm wooden joists (from Wickes) were then secured at right angles to the existing load-bearing ceiling joists. We used small roofing “L” brackets with screws to secure them into place. (Use screws not nails so as to allow easier disassembly.)
These new over-joists were spaced so that the sheeps’ wool roll would fit neatly between them. After rolling out the first layer we then proceeded to apply another layer of over-joists at right-angle to the previous layer. Then sheeps’ wool insulation was laid between these joists. This was then covered in regular attic boarding from a DIY store.
We do not have enclosed eaves so we positioned insulation so as to allow airflow via the eaves. We did not apply boarding right up to the edges of the attic preferring to have unboarded strips all round for access, reduced cost & weight. Having a free flow of air above your insulation will quickly dry up any moisture which might otherwise result in damp (note the unboarded eaves to the left and right of the photo below).
Boarding over loft insulation – electrical wiring must be laid on top of the insulation but under the boards – mark up its position for future reference
This DIY job requires a good wood saw, electric drill (to pre-drill screw holes for the brackets), electric screwdriver (really helps) and a way of counter-sinking the screw holes for the boards. We also added a new loft hatch which had a 100mm plug of polystyrene with a good airtight seal at the edges. We re-used the loft ladder that was already fitted, but had to add good electric lighting before work started.
Electrical wiring for the lighting circuit must be laid over top of the insulation but under the boards. We suggest using a black permanent marker to draw their position and purpose over top of the boards for reference later (the same goes for water piping & stop-cocks concealed by the boards).
This was the most time consuming and awkward task we undertook during retrofit. It was also the most satisfying because of it. It was NOT technically hard. It saved us a lot of money and (at the time) seemed the only way to get the job done the way we wanted it. We were also lucky that we have quite a vertically spacious loft space – keep in mind that an extra 200mm of insulation is height lost inside the attic.
Our project took a long time because we had inset ceiling lights that had to be boxed in and made airtight so as to prevent air leakage. Total cost of Sheep’s Wool = £999, attic lighting = £55 (another DIY job), wood/tools = £618.
© Mark Brown July 2012
Further Information:
Full details of this project are available at Post Carbon Living. There are commercially available systems now such as LoftZone StoreFloor. You can see the results of this loft boarding project at Mark Brown’s SuperHome at Open Days in September or by appointment. Mark is a member of Transition Town High Wycombe.
See Also:
Best insulation
Cavity wall insulation work