For those of you with ICF homes, how did you do your roof? My next home will be ICF, but I am unsure on how to attack the roof.

I'm currently building my ICF home (single story with full walk-out basement - all ICF). I plan to use a conventional roof for my area (central Arkansas) which consists of trusses on 24" centers. I will probably use a raised heel energy truss to get more insulation near the outside walls. For insulation, my current plan is to seal the ceiling plane with ~1" of closed cell spray foam followed with ~12" of blown cellulose for a total R value of ~50. Or I may skip the spray foam and just use ~14" of sprayed stabilized cellulose insulation depending on costs.

Roofing material will either be architectural shingles or standing seam metal (no exposed fasteners) over plywood decking with 30# roofing felt or equivalent. I still haven't decided on which roofing material to use.

Roof trusses will be anchored to the top of the ICF wall using embedded anchors every 4', a treated wood top plate, with 1-1/4" tie down strapping over the truss bottom chords connecting to the anchor bolts using tension heads bolted to the embedded anchor bolts (Tie Down Engineering part #59150 strap, part #59100 double tension head, part #59135 slotted bolt & nut).

SIPS. Not necessarily the CHEAPEST, but you want a great house not a cheap house, right?

What I hope to use for the roof is metal SIPS. If metal SIPS, it would likely be from Chris Kavala due to the great support he’s provided on this forum. Shipping costs could become an issue when there are several wood SIP producers near Indianapolis. Not sure if they’ll be installed on wood trusses or on steel framed roof. The money to build and the plans haven’t progressed that far yet. We are still in the preparation phase.

I’d really like to have the SIP roof come to just the outside of the concrete of the ICF wall. That will allow the outside foam to go up to the top edge of the SIP to eliminate the thermal bridge there. The rest of the gap at the top of the ICF would be foamed to seal any remaining air gaps. Then glue and screw sleepers on top of the SIP roof and cover the sleepers with typical roof sheathing to produce a vented roof over the SIPS. The sleepers would go long to produce the overhang and have small triangle trusses attached to the ICF wall to support the sleepers and soffit. I hope that make sense.

Since we intend to build with ICFs for air tightness and the strength in a tornado area, the SIPS roof, I feel, will be easier to maintain air tightness and hopefully strength, too. While we could go with the sprayed foam approach in a truss roof, I believe using SIPS reduces air leaks and thermal bridges much easier. I’m not sure about the cost of this approach. However, spray foam was around a dollar plus a board foot. That dollar buys a few inches of foam based on a few posts made by Chris Kavala.

The vented roof is really being done for four reasons. One is because I’m somewhat paranoid about roof leaks. The steel SIP would provide an extra layer of protection. Two is something I read on the Building Science web site about vented roofs being better. Third is that I don’t really want to attach all the shingles straight to metal. Fourth when roof replacement time comes, using steel SIPS there shouldn’t be an issue with the SIP in the tear off of the old roof and sheathing should there have been a leak.

Thanks for the replies. I am going to building in central KS, so one main reason for an ICF house is for tornadoes. Will a SIP (metal or wood) roof be able to withstand the high winds that come with a tornado? I know the roof is a very important part of the envelope of the house and I am prepared to do it right the first time, even though it may be more expensive. I'm not saying I have an unlimited budget, but I can finish some interior features down the road to ensure I have a strong and insulated house.

You could go with a concrete roof if you want better protection from tornados. I thought about it, but it seemed it wouldn't work so well on our house design. Also, it is more expensive. I saw several being done in the Caribbean Islands on a vacation. However, they don't get done around my area much for residential. However, the same can be said for ICF and SIPS.

The use of hurricane straps or other appropriate connections on the trusses will make the roof much stronger. I’d glue and screw the SIP or decking, too. Whether it will be stronger than the tornado, I can’t say. You should discuss the issues for strength with an engineer and the costs with your contractor.

I didn't know that hurricane straps/other connections existed. I dont want to build a strong home, and then have the roof pop off and everybody get sucked out. Can a normally built roof be connected/strapped down in such a way that will keep it on during super high winds? Or will I have to go with SIP or a concrete roof such as insuldeck/opdeck/hambro? Thanks

Posted By blavis on 31 May 2011 05:35 PM
I didn't know that hurricane straps/other connections existed. I dont want to build a strong home, and then have the roof pop off and everybody get sucked out. Can a normally built roof be connected/strapped down in such a way that will keep it on during super high winds? Or will I have to go with SIP or a concrete roof such as insuldeck/opdeck/hambro? Thanks

Check out www.strongtie.com for all kinds of connectors. Here's a collection of truss connectors: http://www.strongtie.com/ftp/catalogs/c-2011/C-2011-p173-p176.pdf. Here's the link to the entire catalog: http://www.strongtie.com/literature/c-2011.html.

Posted By blavis on 31 May 2011 05:35 PM
Can a normally built roof be connected/strapped down in such a way that will keep it on during super high winds? 

Yes.  See my post above.  I provided the method and part numbers to do this.  With anchor bolts set at 4' on center and located between every other truss, 1-1/4" wide strap spanning the 4' between the anchor bolts would cover 2 trusses.  2x4 blocking would need to be installed between these 2 trusses to keep the strap tension from pulling the trusses toward each other.

Tie Down Engineering's strap is ANSI rated for 4750 pounds.  The slab anchors are rated for 4725 pounds.  These components are manufactured to HUD specifications with the intent of tieing down manufactured homes in hurricane prone areas.  With my method of having the straps go over the trusses and being rigidly anchored to the top of the ICF concrete wall every 4', the weak link will be whatever material you use to cover the roof deck, i.e. shingles or metal or whatever.

Here is some info on Tie Down Engineering's strap and concrete slab anchors:

http://www.tiedown.com/pdf/d12.pdf

Simpson also makes products for direct embedment in the concrete that then wrap over the truss and provide a secure attachment as well. 

http://www.strongtie.com/products/c...AL-TSS.asp

Another option is ICF Connnect plates embedded in the wall.  The trusses are then set in and secured to the ICF Connect plates.

http://www.icfconnect.com/roof.htm

I like the Tie Down strap method over the top of the trusses because you aren't relying on nails or screws to hold in the wood trusses.  Plus the cost is reasonable (less than the other options listed here) and the installation simple.

Posted By arkie6 on 01 Jun 2011 01:15 AM
Here is some info on Tie Down Engineering's strap and concrete slab anchors:

http://www.tiedown.com/pdf/d12.pdf

Not directly related to this thread, but... Several years ago my brother was involved in the installation of manufactured homes on permanent foundations. He was at a MH conference in New Orleans where, I believe, Tie Down Engineering was demonstrating their tie down systems, the ones shown in the document you link to. Because of the soil conditions in south Louisiana the screw in anchors shown in the document pulled right out of the soil long before the prescribed pull test limit was reached! A bit embarrassing for Tie Down!

Yeah, too much variability when dealing with soil anchors. Not so much with concrete assuming proper placement of anchor bolts and rebar in top course.

arkie6 - it took me a minute to realize what you were talking about. I am a complete noob when it comes to roofs, so after reading your post, i was sorta confused.

Why only anchor every 4 feet? why not on every truss? and what do you mean by a treated wood top plate?

I want to use a strap ( to avoid relying on nails/screws) but i also want to embed the anchor point into the concrete while it is still wet. Is that possible?

Sorry for the dumb questions, just trying to learn as much as possible before I talk with my builder again.

Thanks

Better if the roof get pulled off and leaves the walls in place - then the important thing is seat belts for the occupants!

Posted By blavis on 01 Jun 2011 10:17 PM
Why only anchor every 4 feet? why not on every truss? and what do you mean by a treated wood top plate?

I want to use a strap ( to avoid relying on nails/screws) but i also want to embed the anchor point into the concrete while it is still wet. Is that possible?

Sorry for the dumb questions, just trying to learn as much as possible before I talk with my builder again.

Thanks

4' anchor spacing just seemed reasonable considering I was planning on using  5/8"x10" bent anchor bolts like in the following link:

http://www.fastenal.com/web/product...024&ucst=t

If your roof truss spacing is 24" on center, you could install anchor bolts between every truss.  I would think that a 1/2"x8" or 1/2"x10" bent anchor bolt set every 2' would be more than sufficient.  Cost and strength wise, the 1/2" anchor bolts every 2' is probably on par with 5/8" anchor bolts every 4'.  There would be additional cost with the additional tension heads and slotted bolts set every 2' vs. every 4'. 

In my case with the 5/8" anchors set at 4' and between the trusses, the tie down strap between any two anchors will pass over the top of two roof trusses.  To keep from pulling the trusses together when I tighten the tie down strap, I will cut scrap 2x4 blocking 22.5" long and place between those two trusses.  That will hold the trusses at 24" on center.

I prefer to set the bent anchor bolts before the concrete is poured so I have more control over their placement, but many do set the anchor bolts immediately after the pour while the concrete is still wet.

A treated top plate is a treated pine 2x6, 2x8, 2x10, or 2x12 (width depending on wall width, design, etc) that is drilled and set over the anchor bolts discussed above and bolted to the top of the concrete wall.  The roof trusses then rest on top of the top plate and are typically just toe nailed to the top plate.  In my case, I plan to also bolt the Tie Down Engineering double tension heads to the top plate by placing them between the anchor bolt nuts and the top plate.  This gives me a point to secure the tension strapping that will pass over the end of the trusses.

The following link shows the Tie Down Engineering double tension head set on an expansion anchor.  In my case the tension head will be bolted to the bent anchor bolts set in concrete discussed above and the expansion anchor will not be used (you can purchase these heads with or without the expansion anchors, this link just provided the best photo):

http://www.amazon.com/gp/product/im...automotive

Arkie6. If you're using treated lumber for your top plate please use galvanized bolts, nails, everything galvanized that will be in contact with the treated wood. I've seen too much in the last two years to tell you otherwise. The "new" treated lumber will eat non-galvanized down to the nub. If people could see inside their walls they wouldn't sleep well at night.

Hugh, it is definitely a good idea to consider using hot dipped galvanized anchor bolts with currently available treated lumber, but from what I have read it is not required in dry applications.  Moisture is required to provide a suitable environment for the galvanic corrosion of unprotected steel fasteners.

In my case, the treated top plate will be installed inside the building envelope ~19' above the footing.  I also plan to apply a moisture barrier between the concrete and top plate, but it is really not required considering the distance to the footing (which also has FastFoot under it to further isolate it from the moisture in the soil).  The top plate should remain dry.  I have already purchased my top plate which is copper azole treated pine 2x12s that I am using for my walk boards on my ICF bracing.  I may also apply cold galvanizing compound to the exposed portions of the anchor bolts just to be on the safe side.

Also, the International Residential Code allows the use of plain steel anchor bolts of 1/2" or larger in contact with treated lumber in dry locations.

Here is some info on the use of plain steel anchor bolts with treated lumber in dry applications:

http://www.conradfp.com/pdfs/Arch-T...d-Wood.pdf

Also from the link below regarding ACQ treated lumber:

"When ACQ pressure-treated wood is used for interior applications with continuous dry conditions, where the wood in service will remain below 19% equilibrium moisture content, the performance of fasteners, hardware and other metal products in contact with the treated wood should be similar to that experienced with untreated wood."

http://www.ufpi.com/product/ptlumber/fasteners.htm

We recently did a remodel on a home built in 2000. In expanding the main room the only thing holding the exterior wall up was the roof. The anchor bolts were basically less than half size. Maybe it's the humidity here in SC, but minimum code is just that...minimum. It's worth the ten bucks extra per box of anchor bolts to buy the galvanized.

Hugh, was that wall anchored to a slab on grade or a pier and beam foundation?  Just curious where the moisture may have come from.

Have you priced galvanized anchor bolts lately?

I need fifty (50) 5/8"x10" bent anchor bolts to anchor my top plate to the ICF wall every 4'.

Fifty (50) plain steel anchor bolts will cost ~$125.  Fifty (50) hot dipped galvanized anchor bolts will cost ~$290.  And 80% of the galvanized coating will be in the concrete where it is of no use.  I think I'll get a can or two of cold galvanizing compound to treat the exposed 2" of the anchor bolts.

It was on a perimeter block foundation five block high with the bolt exposed to 1 1/2 inches of treated wood. I just pulled my invoice for the last ab's I bought--5/8x10 galv are $42.29 per 25. 1/2x10 galv are $69.58 per 100. Not beating you up, but you need to look at another supplier at the prices you posted.

Hugh, I live in a relatively small town and the local builder's supply with decent prices (the only one left - the other one closed down last year) only carries 1/2"x6" and 1/2"x8" plain steel bent anchor bolts. They don't even carry any galvanized anchor bolts and won't order them. The prices I quoted above were from Fastenal, which is where I have to order the 5/8" anchor bolts. Either that or drive ~150 miles round trip.