Timber Framers Guild Forums General General Forum Questions How many straps should I install?

I am having a timber frame erected in late August. Originally, I was going to have the timber frame connected to the foundation stem wall with Simposon STHD14 straps that are cast in place with the stem wall pour. However, I realized that would mean almost no room for error in the concrete contractor's measurements. Instead, I will use something like a Simpson HTT22 straps which you bolt in place and then nail to the post. So...I have two questions
1) Is the HTT22 a good option or is there an easier method?
2) How many straps should I install? I have 15 perimeter posts which will rest on the pilasters/stem wall
Thanks.

What are you trying to accomplish with the straps? Are you trying to hold it down in a hurricane? How tall is the building? What kind of "sail area" does it present to the wind? Etc, etc. There are mnany variables here, and thus it's a complex equation with no simple answer. I've said this before, and I'll probably say it again: The stakes are high. If you're looking to save a few bucks by getting some free advice on this forum, you're sure to get you're money's worth. My adivce is to hire a professional engineer to do the math for you to meet the codes and satisfy your building inspector. CB.

The house will be in the mountains. Although there can be 80 mph winds, this is not hurricane or tornado territory. The timber frame structure will be 23' tall. The predominant wind is from the west (coming from the mountain range) and the house projects a 48' face in the wind direction.

My main objective is to prevent the frame from shifting. I'm leaning towards just tying down each post and be done with it. But is the HTT22 an efficient design? This is Simposon's Heavy Duty Tenstion Tie, and a common strap specified in seismic (Los Angeles) and hurricane (Florida) areas.

Does this house have a SIPS enclosure?

These straps will not prevent your construction from shifting. It would have to be proven by calcs. You need to fix your racking walls (those parallel to wind direction). It is very hard to prove bent with pin connections to work as a stiff frame for wind loads.
Straps you suggested work to prevent uplift which may or may not be necessary. And yes, they "sort" of fix the post in place.

an example... stiff portal frames designed to resist sliding forces are to be usually fixed by four, six and more bolts each leg. HTT22 and STHD14 have just one bolt hole.

As Daiku said: The stakes are high.

Michal

Yes, the frame will be enclosed with SIPs (wall & roof) which will be screwed to the posts, plates, rafters, and purlins. I understand the precautionary advice, but can someone point me towards a typical tie down design? Many of the designs I have seen, including Ted Benson's is to use an STHD strap on each post.

There is nothing wrong with straps you proposed. They do a great job to resist uplift or overturning but for sliding just do not work.

Nail/fix your SIPs on bottom end to lower level (whatever is there...basement, concrete slab...). Fixing schedule depends on wind forces.