insulation sizes - idle curiosity

[elmsoft]

shopping around for insulation board for my timber frame , I quite fancy the look of celotex.
But the board size is 450 x 1200 and with (45mm) studs at 600 centres this would give me a lot of cutting and a lot of waste. Surely 600 centres has to be pretty standard so why the 450 width? Does anyone use 500mm centres for joists or stud work?
As I said, just curious.

 

[SimonH2]

I suspect there are just too many combinations of timber size/spacing for any size to make sense. But the size you quote isn't one I recall seeing - 1200 x 2400 is probably the most common size, followed by divisions (eg 600 x 1200).

I've just been fitting some in SOs loft - every space is a different width as the builders weren't too finicky about getting the joist spacing even But you needn't have a lot of waste - after cutting a piece, you use the bit left in the next gap. Eg, with 400 spaced 50mm timber and 600mm sheets - you'd have 350, 250+100, 350, 150+200, 350, and 50 left over to fill 5 gaps with 3 sheets.

 

[elmsoft]

Thanks for taking the trouble to answer. The 450mm is the standard Celotex size and I just think it makes for a lot of cutting.

Like I say 600 centres has to be massively common, but obviously you are right about the variation.
Just idle curiosity- now back to work!

 

[SimonH2]

It's one standard size - but only for 2 or 3 of their products. Most are 1200 x 2400
http://www.celotex.co.uk

I can only assume that feedback from the industry has led them to the sizes they do. Looking again, the 450 x 1200 sizes are for products intended for cavity wall insulation. My guess (and I'm not a builder) is that the 450 is to allow a slab to be dropped in the cavity and then another row of wall ties, another slab, another row of wall ties, and so on - and/or avoid having to build the wall up, drop a slab down, and then build up either side of a protruding slab. 1200 long would make it handleable outside, while a 450 x 2400 would be a bit unwieldy. 450mm would be around 2 courses of standard blocks IIRC.

 

[mfarrow]

Yup lots of different celotex products. GAxxxx comes in standard large sizes.

Other stuff comes smaller and has varied layers and properties to suit the application.