Threaded rod question
GreyWolf92
| Posted in General Questions on
Hello,
Has anyone ever used threaded rod for framing?
I am planning on running threaded rod (in several locations) from the bottom plate to the top plate, for my tiny house that’s being built on a trailer. This is for extra strength, since this will be going on the road.
I’ve noticed there are several types of rod materials – Aluminum, brass, bronze, copper, zinc, titanium and stainless steel.
Would you recommend to use one type of material over the other? I’m leaning towards stainless steel . Will I need to be concerned with condensation at all?
Thanks.
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Replies
Here is a video of some other tiny house builders using rod in the same way I would https://www.youtube.com/watch?v=nsYJNRsGDlA
Grey,
If you do it, use spray foam to cover the threaded rod and nut at the top and the bottom.
Stainless steel is overkill. Galvanized is fine.
Wood shrinks as it dries out, so the "tight" nuts will eventually be loose. I doubt if the threaded rod is necessary (especially if you have well-secured plywood sheathing) -- there are no conventional earthquake concerns if your house is on wheels.
Hey Martin, I'll go with Galvanized. This is just our way of making sure things are extra secure. The house will be travelling on the interstate which puts it through earthquake conditions.
I did use kiln dried lumber. Do you think spray foam is still necessary? Trying to avoid spray foam all together. Was thinking I would use a sealant around the top of rod and bolt and then tape over with tescon vana tape.
Grey Wolf,
I haven't seen threaded rod used for connections in at least a decade. The studs won't fail in tension, so what you really are trying to do is make sure they are attached at the top and bottom. This is what engineers typically spec instead.
http://www.homedepot.com/p/Simpson-Strong-Tie-11-Gauge-16-in-Tension-Tie-HTT5/202193557
Grey,
The point of the glob of spray foam has nothing to do with whether or not you are using kiln-dried lumber. The glob of spray foam is intended to isolate the steel from cold outdoor conditions, to reduce the chance that the steel will be cold enough to become a condensing surface for moisture.
If a few globs of spray foam worry you, then you can craft little hats out of rigid foam, and glue the hats in place.
Good idea Martin. I'll do that.
Hey Malcolm. Yea I've definitely noticed it's not a common practice these days. Since my home is on a trailer and will be travelling in hurricane/earthquake conditions, figured it was worth it. I'm thinking of using Simpson ties as well.
Is there any downsides of using threaded rod that I'm missing?
Grey Wolf,
- Shrinkage. The rods will not stay tight and so by the time it resists the vertical forces they will have already acted on the wooden parts of the structure.
- No continuity with the wooden structure. Unlike the Simpson hold-downs, the rod doesn't take advantage of the stud to sheathing connections tying the structure together.
- Offers only vertical resistance. Which really aren't the forces acting on a moving trailer.
- Thermal bridging. Introducing long steel elements into the framing.
- Overkill. Manufactured trailers and RVs designed for the same conditions as your's will experience are made of thin, flimsy materials, but you don't see them fall apart on the highway.
I build in a high seismic zone. The only connections engineers spec for shear walls here are the Simpson hold downs I linked to, some Simpson straps, closely spaced anchor bolts, and a ton of nails.
Macolm, I decided to take your advice and go without threaded rods.
I will be using the HTT5's and will also be using the H8 simpson strong tie to attach the bottom and top plates to the stud.
Are these usually installed on the exterior side? Once again, I'm just thinking about condensation if it makes more sense to install on the interior.
Grey,
Q. "Are these usually installed on the exterior side?"
A. The Simpson HTT5 is installed neither on the interior nor on the exterior. It is installed in a stud bay.
As far as the Simpson H8 installation is concerned, I'm attaching a Simpson illustration showing the correct installation of the H8 (see image below). It doesn't look like this Simpson hardware is designed (as you put it) "to attach the bottom and top plates to the stud" -- although you may be able to use it for that purpose.
.
Grey Wolf,
The studs and plates are assumed to be tied together by the plywood sheathing, which makes the whole thing act as a diaphragm. To tie the wall structure to the floor joists we use Simpson straps of various lengths, which are nailed right through the exterior sheathing.
http://www.homedepot.com/p/Simpson-Strong-Tie-Z-MAX-16-in-12-Gauge-Galvanized-Heavy-Strap-Tie-HRS416Z/202329571
Two cautions about using them. If they are installed at the same location as the tie downs, by the time they are both in you will have nothing but nails at the bottom of your stud, which compromises the integrity of the connection. They also create an area on the exterior where it is very difficult to fasten battens or siding.
Hi, Have you had an engineer calculate and create a structural plan for your trailer tiny home? Your home will see a 55 mph wind on the front when towing. The smallest all thread or bolts we using on the west coast is 5/8" diameter.
I watched the video. They should have blocked every panel joint on the plywood, they should place the all thread or hold downs at proper shear wall chord locations, the washer is way undersized compared to wood construction. The diagonal steel straps are a waste of money if you install the shear panel.
A structural engineer can design this using math and common building techniques.
I know budget is a consideration but paying an engineer will save money in designing an efficient structure and will give you piece of mind as to it not blowing off on the road.
Tim,
I find the trend of people who don't know what they are doing creating videos of them doing useless things as though they did know what they were doing very annoying.
Malcolm,
We all know what happened: the internet was invented, and suddenly everybody became a journalist and movie director. It's a brave new world! Who needs editors?
After all, there's no reason to spend $15 a month for GBA when YouTube is free.
Martin,
Everything will be fine once grumpy old men like me die out.
Malcolm,
I hope to get too old at some point to be annoyed.
Tim,
That something I'll try and aim for too then.
Side question, sorry. Got what I needed.
Sounds good Martin. So from I gather, the plywood sheathing will take care of my needs. Just because it makes me sleep at night, I going to nail in a tie plate at the top of stud to the double top plate.
If you had to pick, which product do you think would work better?
HTP37Z; http://www.homedepot.com/p/Simpson-Strong-Tie-Z-MAX-3-in-X-7-in-16-Gauge-Galvanized-Heavy-Tie-Plate-HTP37Z/202329565
SP2 http://www.homedepot.com/p/Simpson-Strong-Tie-20-Gauge-Stud-Plate-Tie-SP2/100375012
You need to tie the rafters to the top plate. If the plywood is lapped and nailed on the top plates that should be fine. Any Simpson connector designed for that should work. Simpson has a Catalog that features High Wind Construction Connectors and info https://www.strongtie.com/resources/literature/high-wind-product-guide - you can learn the concepts from that.
Martin, is the spray foam around metal only necessary if it's exposed outside?
For instance, I used the Htt4 against double studs (interior). http://www.homedepot.com/p/Simpson-Strong-Tie-12-3-8-in-Tension-Tie-HTT4/204842329
Is it wise to use a spray foam type material over it or will roxul insulation between the studs offer the same benefit?
Grey Wolf,
No, you don't need spray foam over the hold-downs that you install between your studs.
I think your tiny house project should win the prize for the highest worry-to-square-foot ratio.
Haha well just trying to make sure it's done right. And learning a long the way.