What is the preferred method (for ease of installation and cost) for attaching clear-span roof trusses to the top of an ICF wall? Wood plate on top w/ clips, embed clips into concreete at top, drill anchors into concrete? What works best? Thanks

I'm not sure what is generally preferred, but here is how I am doing it (currently in process, steps 1-3 complete):

1. Set 5/8" x 10" galvanized "L" anchor bolts every 4' prior to the wall pour, insuring that anchor bolts will not interfere with truss location.
2. Install 2"x8" treated pine lumber top plate flush with outside of wall (these were my 2x12 walkboards for my ICF bracing that I ripped down to 8" wide to clean up the untrue edges)
3. Install tie down double tension heads on every anchor bolt between nut and top plate - similar to this link: http://products.tiedown.com/item/ga...head/59100
4. Install 2x4 plated roof trusses with slightly raised heel (provides additional insulation space over top of wall plus allows for strapping over bottom chord at top plate) on 24" centers. Trusses will be toe-nailed or screwed to the top plate initially to hold them in place during installation.
5. Install 1-1/4" galvanized tie down strapping over truss bottom chords at top plate and passing through the tie down tension heads. Will need 2x blocking between every other truss bottom chord between the anchor heads to prevent displacing the trusses when the anchors are tightened via the split bolts. Tie down strapping: http://products.tiedown.com/viewitems/galvanized-strap-hardware-for-housing/certified-galvanized-strapping Split bolts: http://products.tiedown.com/item/galvanized-strap-hardware-for-housing/slotted-bolt-nut/59135

Tie down installation instructions - see page 5 for tensioning directions and illustrations: http://www.tiedown.com/pdf/d12.pdf

Note that I considered running the strapping over the top chord of the trusses for additional strength, but this would likely require a level cut into the truss top chord for the strap that I didn't want to make plus it would require close coordination with the framing crew to put this strapping in before the roof deck is installed. By just running the strapping over the bottom chords, the strapping can be installed and tensioned after the roof deck is installed.

My delivered material cost for the tension heads, strapping, and split bolts was ~$250 for the ICF portion of my home with 192 linear feet of wall (62' x 34').  The 5/8" x 10" anchor bolts cost ~$100.

Jerry - I'm not in a 'quake or 'cane zone so this might not work for all. I cut my inside panel down 5.5" and staple from the inside over the web into a 2x6 ledger (on edge). Anchor bolts horizontally into cavity, usually on about a 5º down angle, tie to rebar about 4" down from top. Trusses are fixed to ledger with framing clips. This allows for placement of all components prior to pour. After tightening the anchors there is room to attach 1" of foam over the ledger to flush it up with the inside face of the ICF. I usually space the ledger from the strongback and screw it to maintain level.

Guys, I'm no expert, but I've been studying the code (20009 IRC) for my ICF house build, and have a couple of notes with regard to my code interpretation on some of the above mentioned items. Perhaps with some engineering, there would be exceptions to these items. Anyway, comments are welcome. Based on the code guidance, I plan to use a 2x10 top plate with threaded rods with nuts and washers embedded at 24 in. OC spacing.


1. The tables in 611.9 regarding wall to roof/floor connections do not indicate allowable spacing greater than 24 in. for the anchor bolts.
2. According to Section 611.9.1.1 regarding anchor bolts, indicates that J-bolts shall not be used for the connections details shown.


Does anyone have a different interpretation of this items? Its worded as if these are requirements if you use the prescriptive method (use the tables and figures) for the design.

A year and a half ago I used a raise heel truss, but instead of placing the truss on top of the wall I installed the bottom cord between the walls and attached the truss with Icf Connect brackets on top of the wall and thru the bottom cord on the inside of the wall. No top plate, no bolts, no toe nails. My engineer said it was much stronger than usual attachment systems so we used a 4" icf for the walls and the cellulose insulation butted up to the icf instead of sitting on top of the wall

Smartwall...would you mind posting some photos of your configuration? Does this affect ceiling height? Does the truss still provide an overhang? Thanks Dave

Smartwall, I like that idea. It provides more for the tension that the code is finally addressing. It requires a little tighter construction allowances, but that shouldn't be a problem. The question still remains about difficulty of construction; is the connector bracket cast in or do yo use tapcons?

Snoslidr, you're right. They really tightened the requirements for 2009. I believe the governing issue is the strength of the wood perpendicular to the bolts. Overkill in MOST cases, as the prescriptive methods use worst-case everywhere. I'll be able to space them out to my needs. But if I just use the brackets directly to the top of the wall, it gets rid of the question, as long as it meets lateral requirements.

I wish I had pictures. When the ads talk about backing up files, I'm living proof you should. Farmboy I went up an extra 12" with a half block and a 4" height ajuster. Made more sense to increase the wall height with icf than to fill the top of the wall with plywood on the exterior. Jerry the brackets are cast in place with the top bracket installed at the end of the pour like using J bolts and the wall brackets installed prior to the pour. You actually have 5 inches in width to play with.

we just got done installing the trusses on my ICF build. After many debates on how to do it (looked at a recessed top plate, dropping the trusses between like smartwall mentioned, and the tried and true full top plate with bolts) I went with a full 2x10 top plate with bolts. It was pretty straight forward and easy. I used a non treated plate to keep it straight and not twisting on my. I installed a high density gasket down, stapled tyvek to the under side of the plate, and installed it into 5/8" anchor bolts at 4' centers which is code acceptible around here. It was nice setting trusses, nice wide space to work off of. The trusses have 14" heals on them. The plates are ripped 1/2" in from the face of the foam. The truss heal aligns with the edge of the plate. 1/2" osb will be installed on the heals touching the bottom of the tails and down over the top plate to tie them down good and double as my insulation dam. It then flushes up with the foam on the exterior to run my siding past nicely. I will still use hurricane clips on the inside of the heal to the plate.

Another way to do this method is instead of keeping the trusses back 1/2", keep them back 2" and instead of osb use 2" of esp. This will give full protection to the heels and if you leave a little gap between the ICF and the foam board you can fill it with canned foam for a pretty good seal. Depending on the venting method you choose for the attic, you could notch the foam board around the truss tails and take it right to the sheathing.

I centered a double 2X8 plate with my 6" Fox forms, which leaves exactly 2" inside and out. The trusses were dimensioned to be flush with the outside of the plate, not the ICF. Since I used raised heel trusses, I sheathed the outside with OSB, adding another layer of connection. I'll put 1-1/2" foam over the outside to bring the wall flush with the ICF, and put a strip of 2" foam on the inside. Local code here calls for 6' spacing on anchor bolts, and toe-nailing the trusses. I put my anchors on 4' centers, and used H-10 hurricane clips. I also had my trusses bumped up to 130 MPH rating over the 90 MPH standard. Codes around here are pretty lax, as are inspections, but I'm the one living in the house. The inspector has commented several times on how 'over-built' everything is.

Install a truss layout with marker on the ICF forms before you pour.
Wet set simpson heta 20 straps on layout on day of pour, with extra straps at girders etc.  Don't forget your king hip trusses...
Set trusses and nail strap.
If it makes you feel good put a piece of 30 lb felt between truss and concrete.

This is characteristic of how CMU wall/truss connections have been installed in high wind areas and is fast and cheap.

Irnivek, What's critical to watch out for when using this approach? Is there much room for error in setting the straps that would affect truss placement? Dave

Dave, Its most critical to have a deep wheelbarrow to contain all the cash that this method saves in labor and materials...lol


Actually, this method is probably not used more because ICF subs who don't do their own framing dont want to bother with it. Extra hassle of truss layouts for no extra pay? Why bother????? Well for the good of the client, I say! Look out for the client, one establishes trust, which is paramount for an enjoyable build.
Although its simply easier to dip a J-bolt, which is about 85 cents we have found a strap is also .85 and one finds that there are never angry calls from framers that "the nuts and washers are missing!"
Also northern wood carpentry framers who haven't ever worked off CMU bond beams or ICF will not be used to setting trusses on an 11 inch wide wall. New things being bad for most men, this strap in the concrete idea is pretty scary for the runofthemill wood butcher. So patience is required. Find out the subs quandry, then give a plausible solution that saves time and money. If they dont agree, hit them with a pressure treated two by twelve if they love them so much.....

So planning ahead is paramount. The day I enter into a contract to provide services, I am offering to dip straps instead of J-bolts. I run through the strap vs. j-bolt-top plate-hurricane clip options, and detail that the GC/owner will have to provide an engineered set of truss plans including dimensioned truss layout at least 48 hrs prior to the scheduled pour date. I also carry enough j-bolts in inventory in case the truss layout/straps don't show up....
Some framers will send someone out to lay out and/or dip their own straps.
Some GC's will dip their own and then brag to all the walkins how his truss connection has direct tie in to the concrete walls.
Some homeowners will not plan ahead, dipping the straps at their own liablity, do them wrong and deal with the consequences accordingly.

Whatever, success can be largely accredited to proper communication of options in the interest of a better finished product at better price, and therefore repeat customers. Then comes the smiling the clapping and the writing of cheques!

We also then laser in a 4 by 4 pad by each strap for top of wall elevation, even if odd spaces don't get burned in on a hot day or when help didn't show up for the pour....

We learned in Florida what the specifications for a strap to truss gap allowance was.....Basically if the layout is a little wrong, scab lumber to the side of the truss and then nail the strap to the scab, and over the truss.
Perfectionists can chisel the top of the truss a little so the roof ply is not held proud the thickness of the strap..... Which reminds me it's best to angle the strap outward a little- perpendicular to estabilshed roof pitch- so that as one wraps the strap over the truss, it doesn't kink and leave a nasty knot....

If the layout is badly wrong, get some retrofit heta straps, tapcon them to the concrete, and never ever make that mistake again.....Most carpenters get it right, most salesmen get it wrong, and go back to dipping J's, or mortgage brokeageing.

Kevin
www.icfinstall.com

Oh, Dave, and the northern drywaller will cry that there is no continuos double top plate to naill to on the ICF walls of the house, and will have to address changing their tactics.
Which reminds me, some times installers use a wood top plate just to get finished wall height so drywall will stack without ripping....

But on the plus side, keep in mind electricians love the no top plate method, as they don't have to drill through anything. Don't worry, they won't muddy the waters by lowering their contract price though...

Just another option in a country that is supposed to have options,
Kevin

So non-treated lumber can be installed on top of an ICF wall as long as a capillary break like tar paper is used, correct?

How do you detail that area to keep thermal bridging down?

Posted By Lbear on 11 Jan 2013 07:26 PM
So non-treated lumber can be installed on top of an ICF wall as long as a capillary break like tar paper is used, correct?

How do you detail that area to keep thermal bridging down?

You don't need a capillary break when you're that far above ground. Thermal bridging with a wood plate isn't enough to be concerned about.

Posted By dmaceld on 11 Jan 2013 08:22 PM

You don't need a capillary break when you're that far above ground. Thermal bridging with a wood plate isn't enough to be concerned about.

I meant a break to stop the moisture of the concrete from being sucked up into the lumber.

Posted By Lbear on 11 Jan 2013 07:26 PM
So non-treated lumber can be installed on top of an ICF wall as long as a capillary break like tar paper is used, correct?

How do you detail that area to keep thermal bridging down?

With 6" ICF wall and ~11" overall wall width with a 2x12 pine or fir top plate having an R value of ~R1.3 per inch, you are looking at ~R14 across that top plate which is not significantly less than the ICF wall itself.  Plus, it only comprises a small percentage of the overall wall area.

We have used the Simpson LTA2 and like the strength. We will attach a 2x4 to each and set with a laser. It requires an extra person pour day and more money for the Lta2. I liked the LTA1 better as it did not go so deep (rebar could be in the way) and the truss sat on metal, but they discontinued the LTA1.
http://www.strongtie.com/products/CFS/LTA2.asp