Not sure how to order timber for shed build

[Ade Daniel]

Hi, new to the forum here. I have a very fundamental question.

It's mainly about whether I should design my building using metric or imperial measurements. I can't work out if the wood I'm looking at is graded and sold in metric or imperial. You say 4x4 inches, for instance - and 50x50cm, etc - but is that wood actually cut on a machine using metric or imperial sizing?

For instance, when designing my 3D model in inches, I had my units set to CM. So: 1inch is 2.4cm. A 4" thickness works out to 10.16cm. I've just looked at some wood merchants online and they are doing all their thicknesses in metric. So now I'm not sure if I have to redesign everything to the nearest centimeters or what.

In other words, is it Imperial sized wood sold to the nearest centimeter or is it actually metric sized wood to begin with?

I don't know if there is some standard across the UK whether they use metric or imperial or whether it varies between companies.

Seems like a small detail to some but it matters to me because I need to pre-plan everything.

Thanks in advance and thanks for your patience.

 

[chappers]

not entirely sure what your asking, but if you went to the merchants to buy finished timber say 4x2 which is in inches it means the timber came from a piece 4 inches by 2inches(100x50mm), that is the nominal stock size, by the time it has been finished it will end up a little smaller at 95 x44- 45mm. If you bought rough sawn carcassing it would be 4"x2"(100x50mm).
As you guessed wood is measured and calculated in imperial but ends up metric, you will note that when you buy stock size wood in metric it comes in some odd sized lengths, say 2.4m rather than 2m it comes in multiples of 300mm which equates to 1 foot.
Off the shelf wood is pretty much exclusively sold in metric nowadays, but the conversion is not a direct mm for inch conversion as explained above.
Just to confuse matters most of us would go to the merchants and ask for a 2.4 length of 4x2 if you are looking at timber dimensions online in metric they will refer basically refer to the nearest inch up so a piece of timber sold as 150mm wide would be called 6 " increasing in 25mm increments but actually measure a bit less than that.
Just found this which may help
Sorry I've just gone round in a big circle there but essentially timber comes in dimensions of 1" increments where 1" =25mm less a bit, usually 4-5mm, if planed

 

[foxhole]

A design model it a little ott for a shed, timber dimension matter little as we use a saw to adjust them.

 

[Ade Daniel]

Yeah, of course its OTT to design to the milimetre, on a computer, a shed! I know that, but it's part of a bigger plan for me, where I get to put in some learning time on the CAD.

I get what you're saying, Chappers. You've totally answered my question so thank you. I thought that might be the case, with the sizing. Now I just have to decide whether to build using rough sawn treated or the CLS pressure treated.

Thanks for the helpful replies! (Y)

 

[chappers]

I would use treated CLS, though not perfect will be truer and straighter than carcassing and just generally nicer to work with.

 

[geraldthehamster]

Just don't go to any supplier and start talking in cm. Stick to mm or m.