Putting insulation under loft boards

[SullyTheGoldfish]

Hi

I've just moved house and and thinking about what to to with the loft. I want to board the loft with chipboard kindly left by the previous owner - they not secured down so I want to screw them into the joists.

The joists are about 7cm in height and have 42cm centre to centre. In the gaps there is some old insulation which comes to between 3 and 5 cm. I would like suggestions about how to top up the insulation as I have two ideas:

1) put polystyrene beads on top of the current insulation up to the level of the joists and screw the boards on top. I know that beads are sometimes used for cavity walls so is it possible to use them in this context too? If so where would i get hold on them?

2) put in proper loft insulation (upto 20cm extra) and put boards on top of that. Clearly this is much more difficult as I would have to put extra joists in to raise above the insultation to put the boards on.

Currently I favour number 1 as it seems much easier. I realise that these days at least 25cm of insulation is recommended but this doesn't seem practical if you want to put boards down since lofts aren't built with joists that deep. What do other people do when faced with this problem?

Any ideas, suggestions or comments would be greatly appreciated.

Thanks in advance

Andy

 

[wedge69]

You can buy polystyrene "boards" that you can slide into the gap, probably easier to do than beads. Have seen tehm in DIY books, but don't know where to get them from, sorry.

 

[masona]

2) put in proper loft insulation (upto 20cm extra) and put boards on top of that. Clearly this is much more difficult as I would have to put extra joists in to raise above the insultation to put the boards on.

This maybe the best way to go, the 3" x 2" joists are not really strong enough to walk on but does depend what you want to do in the loft

 

[SullyTheGoldfish]

Thanks for the replies!

I just want to use the loft for storage so the only walking around I envisage is to find/put things in the hard to reach areas.

are 3" joists too small for this kind of use? How much extra would it be sensible to put on? Is it hard to do?

Thanks again

Andy

 

[masona]

You'll need bigger joists to rest on from any wallplate or on any load bearing wall. Put a small square 12 to 18mm plywood on the wallplate or bearing wall and rest the joist on that to clear the ceiling etc. Give me the span length then I can tell you the size of the joists