I'm about to start building an extension on to the back of our house. Plans have been drawn up by draftsperson, owner builder course done, just waiting on some engineering drawings for garage that I'm getting included at the same time before submitting to certifiers.
In the meantime I'm trying to work out what to use for the bearers and joists. I was originally going to use F17 Seasoned hardwood, or some form of LVL (Red Alert maybe). I did a rough budget based on F17 and some span tables I found.
I've since bought the Seasoned Hardwood F17 Span table supplement and they appear to suggest that no matter what span or size of timber they will need to be two lengths nail laminated.
i.e. FLW of 2400, RLW 4500, with tiled roof and cont. span of 1900 = 2/120X35 bearers. (and may need to go bigger if I can't find 120X35 easily)
So I just wanted to check is it normal that no matter what sized F17 hardwood I choose it will need to be two lengths nail laminated together? I'm sure I had older span tables that showed single bearers e.g. 120X70
On the other hand if I look at LVL's 140X45 seems to be the equivalent so am I better heading down that path as it looks like it could be cheaper due to less timber required.