internal door linning size

[ponyagent]

bit dot com ?

need a new lining and was planning to build new wall with either 89 mm cls or 92 mm treated and 12.5 mm plaster board as thats what i have
but the door linings seem to be 132 mm or 106 mm so nothing seems to fit with either 12.5 mm or 9.5 mm plasterboard

any suggestions please

 

[ponyagent]

http://www.wickes.co.uk/invt/200352


this lining is fine at 131mm but under the nominal size it says 138mm

can anyone explain this?

thanks

 

[Deleted member 174758]

Nominal is the sawn size they start with before the timber is run through a 4-sided planer - you normally loose 3 to 4mm per edge, so 3 x 2in (76.5 x 51mm) nominal would actually be delivered PSE (planed square edged) at about 70 x 44mm in real life. CLS (Canadian Lumber Standard, I think) is somewhat undersize from that because of the North American practice of quoting the sawn size rather than the kilned size on unfinished/semi-finished timbers. Unlike us their mills saw bang to to size rather than oversize (3 x 2in here is sawn at about 3-1/4 to 3-1/2 x 2-1/4 to 2-1/2 in the UK and then kiln dried - which causes dimensional shrinkage to about the right size). That translates into 3 x 2in CLS actually coming out at something like 63 x 38mm and 4 x 2in CLS at 88 x 38mm. This is all part of the joy of working with timber!

If your wall is on 4 x 2in CLS studs with 12mm plasterboard either side that will come to 12 + 88 + 12 dry (or 112mm). Allowing for a 3mm skim that gives you 118mm. If your casings are 131mm finished then all you need to do is buy the casings as kits and rip saw them down to 114mm or so, or get the merchant to do this for you. I wouldn't do this until you've actually got the wall in - the timbers you get and the PB might end up being different sizes again. ot the plaster might be thicker........