Utterly confused by CLS sizes

[Temmy]

Hello,

I need to batten out a wall and create a 50mm depth to be filled with 50mm thick sheep wool insulation. What timber should I use for this? If I search for 50mm CLS I get results which say 50mm x 75mm (38mm x 63mm).

38mm isn't 50mm.

Super confused.

 

[Deleted member 174758]

Finished timber in the UK has alway been sold as "ex-" sizes, e.g. nominal or ex-4x2in (rough sawn), which when machined should come out at about 90 x 44mm. Ex-3x2in would be about 70 x 44mm - 63 x 38mm is really a scant, or undersize. In reality it doesn't often affect work (see below gor one reason)

If you need to batten out a masonry wall, in all probability you'll find that the wall isn't absolutely plumb and may not be perfectly straight, so you will.need to consider packing the battening off the masonry (which would give you the 50mm you desire if done correctly)

If you really want 75 x 50mm finished size timber it is available, to order (special machining), but it will cost a lot more

 

[Temmy]

Finished timber in the UK has alway been sold as "ex-" sizes, e.g. nominal or ex-4x2in (rough sawn), which when machined should come out at about 90 x 44mm. Ex-3x2in would be about 70 x 44mm - 63 x 38mm is really a scant, or undersize. In reality it doesn't often affect work (see below gor one reason)

If you need to batten out a masonry wall, in all probability you'll find that the wall isn't absolutely plumb and may not be perfectly straight, so you will.need to consider packing the battening off the masonry (which would give you the 50mm you desire if done correctly)

If you really want 75 x 50mm finished size timber it is available, to order (special machining), but it will cost a lot more

Thanks for information @JobAndKnock. Am I right in thinking this might be just the ticket for what I'm looking for? I don't see anything here about differing finished sizes.

Arrow CLS Timber Batten 2400mm x 75mm x 50mm - TIMCLS5075

Structural timber perfect for use in stud wall timber partitions and many other framing projects. Planed surfaces with eased corners to provide a precision finish. Softwood planed on four sides with rounded edges for easy handling Strength graded Kiln dried for extra stability Ideal for...

www.walls-and-ceilings.co.uk

 

[blup]

Wickes do good value CLS 63x38mm, there is usually sufficient choice in store to get straight timber, better than ordering online which risks the the supplier giving you any old tat.

Currently 2.4 metre lengths are £4 at wickes

Blup