Mitek "Studlok"

[Toby43]

Anyone got experience with these tie-downs? or something similiar?. I'm starting to see Prefab timber suppliers using these.
They are basically a screw fixed down through timber top plate into the end grain of the timber stud. I know most timber codes provide some sort of capacity reduction for fixings into end grain (AS1720 has 40% reduction), but I'm just not a fan of a primary load path having end grain fixings. It is mainly the installation causing splitting and the possible tendency over time for the timber to split that concerns me, rendering the connection useless.
Any thoughts/experiences appreciated.

Cheers
Toby

 

[ShawThing]

I haven't come across these before but you could add this thread to AS/NZS Code Issues?
We wouldn't have much need for them in QLD where we have full height rods connecting the top plate to the slab.

 

[Agent666]

They seem to be being used quite a lot here in NZ as well. In NZ the std fixing is 0.7kN or something similar for top plate to stud. Our non specific code specifies 3x90x3.15 power driven nails into the end grain for this condition, but allows you to match equivalent capacities. I initially wondered about having the single fixing and stud able to twist. But I guess clamping effect with the screw provides plenty of friction.

What if not end grain fixing is the standard practice in AU then?

 

[Toby43]

Yes nailing would still be done in the end-grain, but for lateral loads only, with "Studlok". In low wind zones, typical tie-down practice is for galv. strap to be looped over the top and bottom plate and nailed each end to the studs (i.e. nails in shear). This strap however gets in the way of cladding (needs planing in to be flush and cladding fixing "bounce" back at ya).
Back to the "Studlok" - Interestingly enough I noticed the American Wood Council-NDS has prohibited wood screws for structural use in withdrawal from end-grain since 1944 (I may be wrong, but maybe some-one more familiar with the AWC-NDS may chime in.)
Cheers
Toby