basic timber sizing queries

[climber101]

was hoping you could help me out again please with some basics

when talking about

a) 50x150 C16 timber I have found actual sizes 45x145mm or 44x145
b) 50x100 is 45x95mm
c) 50x 200 is 44x195mm

I’m understanding the 50/150 etc is the prefinished size and the actual size is the finished or ‘regularised’ size. Fine, however when I have been looking at joist hangers and truss clips in builders yard they seem sized on the prefinished sizes and a tiny bit slack fit.

So my questions are

1) do you put shims in the side of slightly oversized joist hangers or truss clips to tighten the fit as well as nailing through - I doubt this – that said I have just found on internet “new range” joist hangers to suit regularised sizes- what have people been using before what appears to be a relatively new product I’m thinking.
2) how often do people ever get timber machined to a finished size of say 50x150? And would I get laughed at asking for same
3) as well as getting joist hangers to fit what triggered me asking my second point was that when I looked at my engineers calcs on one of his calcs it works out ok for an exact size 50x100 but not for a 45x95 – (I’m sure there will be factor of safety in there and it’ll be ok but starts to wonder about going up a size unnecessarily…)

Many thanks in advance for further advices

 

[^woody^]

I think the pragmatic answer is ..... buy the timber and hangers from the merchants and just nail the timber in.

That's what is done

 

[Shytalkz]

The SE should be designing for regularised sizes, not sawn sizes. I know: some tw@ of an LA checking engineer just picked me up on it

(Like it makes a 'kin difference in the design, ffs...)

 

[anobium]

Just ask your timber merchant for sawn, or maybe rough sawn in your neck of the woods, sounds like you have been getting or looking at pse, in other words planed.

 

[Thermo]

No there is a difference between sawn and regularised. sawn is the traditional old fashioned version that is virtually the sizes it says ie 50 x 100 etc. regularised is (as far as im aware) a fairly new version of sawn timber that is almost halfway between sawn and prepared (hope that makes sense!) and is slightly smaller than the sizes referred to.

 

[Shytalkz]

Sawn
Regularised
PSE

 

[stuart45]

Regularised is just to make it easier for the chippies to handle. You can still use sawn if you don't mind the splinters.

 

[mikric]

The SE should be designing for regularised sizes, not sawn sizes. I know: some tw@ of an LA checking engineer just picked me up on it

(Like it makes a 'kin difference in the design, ffs...)

Ah thats why you hate them Shy , yep sounds a tw@t to me too.
Was it something really critical ?????

 

[climber101]

Thanks again everyone for comments, very interesting. I’m thinking I’ll be going for the regularised timber I have seen as that appeared to be the only timber I saw that all the pukka looking C16 or C24 stamps on it. (The sawn stuff I saw didn’t have C16 or C24 stamps on it and whilst I’m sure it would be absolutely fine the fact the timber merchant couldn’t tell me any more than “it’s treated sawn” wasn’t convincing me of what type of wood and strength it was). On another note I’m thinking I’ll get another SE to check some of the calcs as from my basic review of the calcs it looks like if I go with actual regularised sizes it would mean I need to go up a size for some of the timbers

Well impressed with everyone’s help on this forum to date!

 

[Shytalkz]

Stress-graded timber has a stamp on it; no stamp, no grade, unless it's been visually graded by a qualified person, which invariably is not some bloke in a donkey jacket at the timber merchant's yard. You don't need to go up a size, just use the regularised size and grade of that specified by the egineer.

@Mik: way before that, they got on my threes. That's just the latest one to p*ss me off. Invariably, they are sprog graduates, who can - through no fault of their own - do nothing other than slavishly follow the book. They aren't adequately supervised by experienced SEs, so it's more often than not a case of the tail wagging the dog.

With all the risk assessments, ISO9000 checks etc undertaken these days, third party checking is an anachronism. There might be the odd apparently dangerous structure that gets flagged up through the LA/3P checking system, but as a percentage of the whole, it must be miniscule. Sledgehammers and nuts spring to mind. Not to mention a great deal of wasted, unfeeable, time.