Laying kingspan or xtratherm boards

Gra10

Hi I'm thinking of laying 100mm of kingspan boards instead of the fibreglass or rockwool as the joists are 150 mm deep.

A friend of mine has done it and said it was easy enough. Jigsaw and away you go. I've noticed people mention you need to seal it between the joists. If so, how why and with what?

I also want put down the old laminate floors from downstairs up in the attic so I can walk around and for storage. That means there will be a 50mm air gap. Will this cause any problems with condensation etc?

Chadwicks price is 40 euro for 100mm thick 8ftx4ft boards but take some off depending on how much i buy......65 square metres! I think paying extra is better in the long run.

Can anyone answer the above questions for me please especially about the sealing and making it air tight. Thanks mill

slimjimmc

Not sure exactly what your friend means by sealing but you generally cut the boards so that they're a tight fit.

BTW laminate flooring is merely a hard wearing cosmetic covering. It is not designed to support weight and is not strong enough. Any attempt to walk on unsupported laminate could result in its collapse.
You need to use wooden planking or sheets of ply/osb to make a floor strong enough for walking and storage.

Carlow52

The sealing os usually due to a sloppy cut/join so people use expanded foam..
I would not use any form of rigid insulation, consider some thing like warmcel which is a loose insulation which u spread out easily.

In terms of the depth attic insulation is the best value for money around so I would fill the 150 as a minimum.
You cant use the laminate as it is not designed for that

Smcgie

Have a look at the kingspan thermafit. It's cut/grooved out insulation that Slots in between the rafters or joice.

It will save you hours cutting

http://www.insulation.kingspan.com/uk/pdf/product%20_selector_2009.pdf

Gra10

Thanks.

The only reason I'm going for rigid board is because 150 mm of rockwool or fibreglass isn't good enough. I know you can go 300 rollsbut then I can't lay any boards on top for flooring.

The rigid board is insulating the water tank and has done a great job. Finally if I wad to lay it can you leave the old fibreglass underneath or does that have to be dispose of?

Cheers for the advice

Smcgie

Gra10 wrote: »

Thanks.

The only reason I'm going for rigid board is because 150 mm of rockwool or fibreglass isn't good enough. I know you can go 300 rollsbut then I can't lay any boards on top for flooring.

The rigid board is insulating the water tank and has done a great job. Finally if I wad to lay it can you leave the old fibreglass underneath or does that have to be dispose of?

Cheers for the advice

Leave it there does no harm