What is the best solution to putting a treated wood top plate on top of an ICF wall for roof attachment?

Typically what I see is just 2x6 treated lumber that is anchored down with J-Bolts set in the wet concrete. The treated wood top plate is then set down on the cured concrete and the bolts are anchored down. Countersunk bolts since a flat smooth surface is needed for the roof SIPs.

Is a 2x enough of a "bite area" to hold down and screw a SIP roof to?

Is there better lumber to use than simple green/brown treated lumber?

It will depend upon the wind speed criteria. I would rather see a full ripped 8" on an insulated top plate and staggered structural screw connections to the top plate as the sip osb is only so strong. There are numerous things from Simpson but all require more planning and most would rather have it simple then complicated.

Yep, it depends a lot on your wind/uplift requirements. I know those long timberlock screws are all the rage, and they look pretty stout drilled down thru a double headded stud wall. Screwed into only 1.5" of treated lumber dosn't sound all that strong unless you use a LOT of screws, with something to distribute the force across the top of the OSB so they just don't pull thru. I wonder if they make a tapcon long enough You could then probably pour the ICF wall to the roof angle and skip the sill board alltogether... At any rate, you may need to add some embeded straps that extend up thru the panel and are folded over and attached on the top of the panel to meet a high uplift requirement.

I am building a conventional roof and am skipping the sillplate alltogether using HGAM-10 brackets to attach the trusses to the flat poured wall top...

Ronmar, how do you plan to protect the untreated truss bottom cords from being in contact with moist concrete? The concrete will be moist for several months while curing and may also experience condensation too.

They have this wonderfull new stuff called Vicor I will be putting a small strip of vicor flashing where each truss and the associated blocking rests. Easy to do, but probaby overkill as at the rate I am building, the CC moisture content will be pretty low by the time I get to closing things up. Not too worried about condensation, as ultimately all the CC not covered by truss and blocking will be covered with insulation...

I found a 4x6 piece of treated lumber called Browntone ACQ

It's actual dimensions are 3.5" x 5.5"

This surely is more of a beefy piece of lumber than the 2x6

I've posted this before. My preferred method of truss attachment is to skip the top plate and put block outs in the icf to accept the trusses with Watkins hangers holding them in place. Where the wood contacts the concrete we bend aluminum trim material to set the bottom of the truss on.

I like that how that method sounds, smartwall. It would also close the underside of truss enough to spray foam the roof at that joint without having to place some other material for a back stop.

Exactly, you end up with continuous insulation coverage. I prefer cellulose on the basis, you get far more bang for your buck.

Ronmar, I fully expected that you had this well addressed, but I also figured it would not hurt to ask and confirm :-)

Smartwall, that sounds like another great ICF innovation! Do you have any photos of this detail that you can share? We still use PT 2x sill plates (sometimes even 11" wide), sill foam seal and 3x3" foundation washers. We typically toe nail the trusses to the sill plates while setting them and then followup with Simpson H2 ties (sometimes on both the interior and exterior sides). Trusses always have at least a minimum energy heel of 6" and we prefer cellulose too. Overall building design and uplift requirements dictate each specific detail.

Posted By Lbear on 03 Jul 2016 01:49 AM
I found a 4x6 piece of treated lumber called Browntone ACQ

It's actual dimensions are 3.5" x 5.5"

This surely is more of a beefy piece of lumber than the 2x6

3.5" of material to screw into sure sounds better than 1.5" of material. I am curious, How are you planning to match the sill to the SIP roof angle?

In the SW we are mostly slab and our HVAC is in the attic space. Making it conditioned space saves a lot of energy. No more ducts traveling through 150 degree air. If you have any pictures of this detail I would love to see it.

ronmar, You know I wanted to suggest tap cons when I read the first question. ; ) Thanks.

Maybe I'm missing something. But why is everyone trying to isolate the truss from the concrete? There is certainly no code requirement to do so if wood is greater than 18" from grade and while I would still use treated for sill plates even if above that amount a considerable bit, when you're as far from grade as a roof truss, I just don't see the need.

Posted By ronmar on 03 Jul 2016 01:41 PM

3.5" of material to screw into sure sounds better than 1.5" of material. I am curious, How are you planning to match the sill to the SIP roof angle?

Most likely the ICF contractor will be able to pitch the ICF during the pour to the 2:12 pitch on the shed roof design. Sort of like when they do it to a gable roof ICF pour.

So that will leave me with a concrete top wall area that slopes from 12 feet at the front of the house to 9 feet at the rear. The wood top plate would then just anchor into the bolts set during the pour and the wood top plate would simply just follow the pitch of the set concrete. The roof SIPS would then just lay down on top and screw down into the wood top plate.

SEE BELOW: (of course this is a gable end but the same principle - just slope the ICF on the shed roof angle during the pour, set and you have the proper pitch)

Posted By Nashvegas on 03 Jul 2016 06:41 PM
Maybe I'm missing something. But why is everyone trying to isolate the truss from the concrete? There is certainly no code requirement to do so if wood is greater than 18" from grade and while I would still use treated for sill plates even if above that amount a considerable bit, when you're as far from grade as a roof truss, I just don't see the need.

Well if you don't see the need, why not use untreated sill plates that far up? They would probably not shrink as much:)... You can get the same or better restraint other ways, and not embeding anchor bolts makes pour day dead easy, just concentrate on trueing-up the wall and trowel the top flat.
Adding something between wood and CC falls into the cheap insurance catagory IMO... You are of course right IRT the requirements, but since it is so easy to put something between the wood and CC, why not do so just in case any exposed CC ever finds itself below the dew point and exposed to moist air. If it does, it at least cannot transfer that moisture to the underside of the truss or SIP OSB paneling...

Posted By ronmar on 03 Jul 2016 07:32 PM

Well if you don't see the need, why not use untreated sill plates that far up? They would probably not shrink as much:)... You can get the same or better restraint other ways, and not embeding anchor bolts makes pour day dead easy, just concentrate on trueing-up the wall and trowel the top flat.
Adding something between wood and CC falls into the cheap insurance catagory IMO... You are of course right IRT the requirements, but since it is so easy to put something between the wood and CC, why not do so just in case any exposed CC ever finds itself below the dew point and exposed to moist air. If it does, it at least cannot transfer that moisture to the underside of the truss or SIP OSB paneling...

I can use 4x6 Douglas Fir instead of treated wood (which does tend to twist and move as the treatment product dries out)

So you are saying just put a foam sill plate protection between the concrete and wood/OSB SIP?

How would one anchor the roof SIP into the concrete wall? One needs a wood plate to screw the roof SIPS into.

Yes, we use a raised heel truss with the heel sitting between the walls and not on top of it. It allows the use of a 4" icf. Sorry I don't have pictures. As far as separating the wood from the CC we do it just so there is no questions. It's a simple detail with very little cost beside some aluminum coil stock which we always seem to have. You can use ice and water shield also. I use KD wood for my bucks with I and W on the back side. Simple and cheap.

If you ever have a chance to grab a picture of this detail I would love to pass it along to my builder. Thanks.

Posted By Lbear on 03 Jul 2016 11:35 PM

I can use 4x6 Douglas Fir instead of treated wood (which does tend to twist and move as the treatment product dries out)

So you are saying just put a foam sill plate protection between the concrete and wood/OSB SIP?

How would one anchor the roof SIP into the concrete wall? One needs a wood plate to screw the roof SIPS into.

That far(wall height) above grade, you shouldn't need PT lumber. Sill gasket or Vicor material between the CC and sill should be fine.
As for attachment, In the case of OSB paneled roof SIPS it probably makes more sense to use a sill board and a bunch of those long screws and large diameter washers to spread out the uplift load across more of the OSB skin, unless they have some integral structure that accomplishes this load dispersal using fewer fasteners. With Too few fasteners, I could see a big wind just ripping the roof up over the heads of the long screws where the load would be concentrated. If there was some structure in the roof panels that runs where the roof panel attaches to the wall that you drill thru, to disperse the load from a lesser number of fasteners, I could see threaded embedded anchors being set in the wall with a jig on pour day. You then pre-drill the panel to match the anchor spacing and lower the panels over the anchors(after adding the gasket/vicor to the top of the wall). Use a coupler, bolt and large cupped washer to screw down onto the fasteners after you foam the holes around the anchors. I suppose if they were threaded and were left slightly long you could just use the nut and cupped washer and cut off any excess after the roof is torqued in place. This has the advantage of setting the SIP right down on top of the ICF foam. Of course all this is subject to getting enough roof restraint from a given number of anchors thru the SIP panel...
You can get the same thing(sip right down on top of ICF foam) with a sill beam if you recess the beam down into the ICF so it's top is flush with the top of the block... this would save you gong back and insulating the sill beam...