I had a conversation recently regarding the use of timber floor joists, a manufacturer asked why I always specified sawn cut joist, why did I not allow natural un-sawn logs, after all there are loads of old houses that were built with them and they are still working fine.
The simple answer is that un-sawn timber would not fit all the metal joist hangers and I know of no standard I can use to size the timber for span. But I love the idea of using timber like this so I intend to look more closely at the idea.
As an alternative to sawn timber joists, I have been specifying I-joists, the engineered timber joists with a top and bottom string of timber with a ply or similar web, the span tables for these are all over the web. I like these simply because of the span, but sustainably they have to be looked at. Take a look at James &Jones they have a typical spread of products, I have no tie to this company, they just have a good site.
Take a look at the other type of I-joist the ones with metal webs, these allow for greater use of inter floor trunking and air distribution and pipe and cable runs to be hidden away and designed for, with specific access traps, and service trays. The passive house presentation I went to at the begining of the year showed these as standard.
Jon Pickup gave me a set of vectorworks CAD files for these all in different sizes, I realy need to make these up into a 3D format and create a sample beam.
Today's picture shows the underside of an i-joist floor, notice the t&g boarding. s for CPD there has to be a good half hour just following up my blog by looking for these products on the market, most timber mills seem to have a good selection, as for self build, the metal webs opens up a raft of advantages, but be aware of certification, making them up your self might bring problems, but it's an interesting thought.
Simpson Strongtie, have a large range of metal I-joist hangers and details, and again I have no tie, (pun) they just have a good site.
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