Monday, 4 January 2016

tie-downs and connectors

Before we started working on the roof, we decided to increase the structural integrity of our frame. A lot of it has been learning-by-doing.
After installing some tie-down fittings (e.g. double-sided stud-ties) we found out about even better ones (e.g. hold-down brackets plus bolts). As it didn’t make much sense to remove the fittings that were already in place, we ended up with a bit of an overkill in some areas.

We used:
  • Threaded rod to connect the bottom of the trailer frame to the top plate of our building. Ideally, the threaded rod should have been made of high tensile steel, as that is common in buildings in cyclone-prone areas. However, we couldn’t find the high-tensile rods anywhere in Perth and as we didn’t have time to ship them in, we thought we’d at least use the standard threaded rod. We thought it's still better than using none at all.
  • Hold-down brackets, bolted through the bottom plate and trailer base and then screwed sideways into the studs.
  • Double-sided stud-ties, to connect the top and bottom plates with the the studs.
Hold-down bracket on the left, two double-sided stud ties, as well as
threaded rod connecting top plate to the trailer frame.
Probably a bit of an overkill, but no point in trying to remove the stud ties now...
  • Speed bracing (which comes in long rolls), to reinforce our little wall at the rear. Ideally, this should diagonally connect the top and bottom plates, but the two little windows on that wall were in the way, so we ended up with a bit of a free-style version. We made sure to wrap the bracing around a corner to connect the small wall with the larger walls, and also to wrap the bracing around the trailer base.
Speed bracing on the rear wall.
The bathroom and loft windows
got in the way a bit!
Speed brace wrapped around a corner and underneath
the frame of the trailer. Double-sided stud ties connect the bottom
plate to the studs.


  • Bugle batten screws in a variety of lengths to connect the structurally important stud connections. We became a huge fan and ended up screw-joining many of our noggins with them.
  • Uni-ties to tie down some of the rafters to the top plate, in particular the rafters at the short ends of our roof that might be experiencing strong wind loads.
A uni-tie wrapped around a rafter.

If we had to do it all again, we would use the nail gun just for pinning, simply to make assembly of the frames easier, and then use bugle batten screws to join all connections of the frames. As tie-downs, we would probably only use hold-down brackets (plus the necessary bolts and screws) and high-tensile cyclone rods. If our windows and wheel arches weren’t in the way, we would have used a couple more of those threaded rods going all the way from the top to the bottom. 
The double-sided stud-ties we used didn’t seem to have a very deep grip and also created thermal bridges bypassing the complete wall insulation.
Speed-bracing makes sense in some situations, but bracing requirements of each wall need to be looked at individually and bracing them with structural plywood sheets, either on the inside or outside, should do the job in most situations. 

We chose the connectors and tie-downs to the best of our knowledge (and from the limited range available in Perth...), after researching what is common practise in timber-frame buildings in Australia, New Zealand and the States. We're pretty happy with how it turned out but wouldn't go as far as saying that this was the best way possible. So let us know what you think, what other cool connectors you have seen or used and how you liked them!

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