Strength grading for small cross section timber

[Martin Gillie]

Is anyone aware of timber grading systems for small section timbers - 50x50mm (2"X2") or less? These fall outside the usual C16, C24 system I am used to in the UK/EU. Maybe for non-structural contexts?

Reason: client wants a geodesic greenhouse in timber.

 

[ANE91]

Interestingly, clear wood specimens are tested at that size, per ASTM D143.

SPIB’s National Grading Rule allows for 2-inch by 2-inch but no smaller.

 

[Greenalleycat]

Our code has "No1 framing" grade which is basically ungraded landscaping timber I think
You may have some equivalent?

 

[rlmengineer]

Would any fasteners have enough pullout capacity needed for lateral or uplift wind forces, plus the potential of fasteners splitting the 2x2 lumber?

 

[Martin Gillie]

Would any fasteners have enough pullout capacity needed for lateral or uplift wind forces, plus the potential of fasteners splitting the 2x2 lumber?

This is the next question! In principle edge distance are sufficient for small screws/nails at 45mm but...

 

[XR250]

yea, I can't imagine getting fasteners to work for this unless you had some sort of receivers they frame into

 

[SWComposites]

Use thru bolts, not screws into the 50x50mm sticks.

 

[Martin Gillie]

Use thru bolts, not screws into the 50x50mm sticks.

Why, out of interest? Thinking screws, possibly pre drilled, would give a tighter connection and same/greater strength for a given diameter.

 

[SWComposites]

Because screws have a tendency to split the wood, even predrilled. Bolts can be torqued down to give a tight connection (use large washers), and a solid shank bolt is stronger in shear than a threaded screw.

 

[ANE91]

Because screws have a tendency to split the wood, even predrilled. Bolts can be torqued down to give a tight connection (use large washers), and a solid shank bolt is stronger in shear than a threaded screw.

Precisely because of wood’s propensity to split, the traditional design philosophy is to use more, smaller fasteners. I would never use a bolt on something this small.