SIPS vs Blue Board roof

[shinnlinger]

Folks,

I am building a strawbale TF and the frame is just about together and I am starting to think roof.  I was going to go with the stressed skin panels, but like all good projects, $ is getting tight and I was thinking of throwing down OSB on the purlins and cover it with heavy felt/rolled roofing and come back later (maybe years)and stack on 3-4 layers of 2" blue board and 2x rafters (I have a GREAT idea how to do this in my head, but feel free to weigh in here)  My logic is the blue board idea is half the $ but twice (at least) the work, but proably not quite so good.

The pendulaum is now swinging back to tightening the  belt and getting panels, and to make this a fair argument, I wondering if any of you had a good source for panels in New Hampshire?, opinion on how thick (6 vs 8"?  can you still get "seconds?" and is it worth the savings?  Can you still get drywall on one side OSB on the other?  And how have you dealt with "panel creep" on 10/12 roofs? (again I have a BRILLIANT idea here of using a 2x cleat over the bale wall and sesmic strapping running along the peak)  I supposed I wouldn't mind hearing about what kinds of wire chases you had installed in the panels.  I have a 5 ft knee wall and was thinking it wouldnt be necesary to deal with wire in the roof, but I dont want to be sorry.

Thanks for your opinion.

[mudburn]

Shinnlinger,

I like the sound of straw bale timber frame! I'm building one of those. It's a somewhat slow process since I'm doing it as I can pay for it (no debt). The frame is up and I'm still working on getting the roof on. Here's what I've done and am doing for insulation in the roof. I have a cathedral ceiling. I sheeted it with 1x's of mixed wood (oak, hickory, and locust). I put tar paper on top to keep the rain out, at least some of it. It still lets some moisture under to the wood which has caused some problems with the wood swelling. Since getting the ceiling boards on, I've been getting things ready for the roof, which will be metal.

Here's what I'm doing. I'm framing a 10" space above the ceiling boards, using 2x3 rafters I milled several months ago and short 2x6s to create the 10" space. I'm putting these on 2' centers. On top of the 2x3 rafters I'm sheeting the roof with OSB and a moisture barrier. Then I'm running 2" vertical strapping and 4" horizontal strapping to which my metal will be affixed (the strapping is to deal with condensation issues.

Okay, the insulation part. In the 10" space I'm having a friend dense pack cellulose insulation. Dense packed cellulose actually creates a vapor barrier and is air tight. There are advantages to that, of course. With the 10" of dense pack I'll have an R-value of nearly 40. I could've gone with more, but the friend who will blow in the cellulose does insulation work and consulting, and he doesn't think I need more.

Other options might take a little less time but more money. For my project, money is the bottom line. It's a do it yourself investing a lot of time kind of project.

Don't know if this helps or not, but there it is.

Darryl

[shinnlinger]

MUdburn,

I do like your idea and it is good food for thought.  At one point I was thinking of framing something similiar to what you are doing but putting straw bales in there instead.  YOur idea Is probably alot more practical though and I propably should compare a blown in guy (Or can I rent one of those blowers?)  I also have alot of used pink fiberglass that is going to get landfilled if I dont use it up.

Any one use those two part foam cans( the size of BBQ cylinders)?  Seems expensive, but maybe worth it?

[mudburn]

I thought about straw bales for roof insulation, too. Then, I considered the weight and thought, what if I ever have a leak? Those bales would get even heavier. They also really need to be plastered (cement, lime, or clay) to help with their fire resistance. So, I moved to something else.

You can't dense pack cellulose with one of the blowers like from Lowes or Home Depot. Dense packing will put in 3 to 4 pounds per square foot. They can blow a hole in drywall. Not your usual fluff machines. My friend is going to blow mine in for cost of the materials, gas to drive here, and some beer! Not a bad deal (I offered to pay him, of course). He can also get the cellulose for cost, about half the price of Lowes. You can do some reading on dense pack cellulose online. That's where I learned about it, actually, and then talked to my insulation guy friend.

Darryl

[shinnlinger]

I will look into building rafter "trusses" like you are doing.  I have a mill so the wood is cheap and I have "free" axcess to a crane to swing them in place.  Might be the ticket...but going be a real wide fascia board!

[tim1234]

Any one use those two part foam cans( the size of BBQ cylinders)?  Seems expensive, but maybe worth it?

Those are called Froth Packs by the people who make great stuff. 

I priced out doing my roof with the biggest packs (the 20 lb BBQ tank size).  It was more expensive than having it contacted out.  The pro's showed up with 4 50 gal drums of the stuff ( 2 part A and 2 part B).  They sprayed my entire roof in 1 day. 

Here's the thing about the froth paks....if you stop spraying for more than a minute, the tip is toast.  The foam will harden in the tip and then you have to replace it.  That's why they give you a handfull of different tips with each kit.  Also the temperature needs to be just right or the foam doesn't expand well.  I found it difficult carrying around the 2 cylanders in my rafters with fogged up goggles on and with specks of foam on them trying to spray in some small areas the pros missed.  I even fell out of the rafters.

If you want to go with sprayed in urethane foam...contract it out.  The pro's are slow in the wintertime because they usually spray commerical roofs outside before they put down an EPDM rubber roof.  It's tough to do in the winter (although I didn't check where you are from, so It depends on how cold your winters get.)

Tim

[shinnlinger]

Tim,

Thanks for the first had account of the froth packs, your experience is what I predicted...let the pros do it. 

I have seen the foamers spray on the inside of stud walls, but Did you foam on top of a beadboard timber frame? I suppose a truss rafter would work of I could get the guys to climb around outside on an 10-12 pitch, and I doubt they would want to do that with weather in the single digits, but I wont be ready to do this tommorow, so it is worth a few calls.

Mudburn,

Can they pack the dense stuff in from one end of a 22 ft bay? Or would I need to drill holes in the OSB?  I plan to put plaster board on the inside between the purlins when I am ready for interior, so a hole wouldn't be the end of the world

[Thehardway]

Just thinking out loud here, not putting down any ideas OK?  What happens if you get a leaky seam or a leeky screw and that dense packed cellulose gets wet?  That's some heavy stuff in wet form and how would it ever dry out?

[mudburn]

Can they pack the dense stuff in from one end of a 22 ft bay? Or would I need to drill holes in the OSB?  I plan to put plaster board on the inside between the purlins when I am ready for interior, so a hole wouldn't be the end of the world

From what I understand, when dense packing, a hose is inserted and can be run in however far an opening allows. It is run to the end, then the cellulose is blown in. When it reaches the desired density (set on the machine) it stops flowing, and the hose is then moved back, filling the next area. Apparently, it flows kind of like water from these machines, filling gaps and cracks. For my installation, we'll insert the hose from the peak, run it down to the eave, and fill from there.

Here's a website with a brief explanation: http://www.weatherization.com/densepack.html.

What happens if you get a leaky seam or a leeky screw and that dense packed cellulose gets wet?  That's some heavy stuff in wet form and how would it ever dry out?

You don't want that. Of course, you don't want your roof to leak with whatever system you use, but some would be more tolerant of leaks I reckon. My system will employ a metal roof which will have a commercial coating after installation (done by my insulation friend -- another one of his businesses). I'm also going to use silicone on all the seams when installing the metal. It will have a 2" ventilation space under the metal above a moisture barrier on top of sheets of OSB. I intend for it to be water tight. I don't want any leaks.

Darryl

[nsmike]

This link is to a site that shows a roof system that uses 4" rigid urethane foam it probably could be adapted to blue foam insulation. http://www.classicpostandbeam.com/materials.php
Mike

[shinnlinger]

MIke,

Does the diagram they show make sense to you?  I can't beleive only 4 inches of anything is sufficent in New Hampshire, but it looks like they are sandwitching the urathane between verticle strapping and the beadboard/purlins and then somthing else (OSB?) goes on the straps and then asphault roof. 

I was thinking of something similiar with the blue board, put down OSB (plaster board inside later, instead of bead board) roofing paper and then stager the seams on 3-4 glued layers of 2"foam and then vertically strap and screw through to the purlins/rafters with some serious screws and a cleat running the lenght of the building over the bales to help keep it from sliding and the vertical straps seismectly taped over the top of the roof also and then run horizontal strapping on that and tin it over.  A fair bit of work for sure, but I guess it all is.

Any one out there like the stressed skin panels?

[tim1234]

Shinnlinger

I have seen the foamers spray on the inside of stud walls, but Did you foam on top of a beadboard timber frame? I suppose a truss rafter would work of I could get the guys to climb around outside on an 10-12 pitch, and I doubt they would want to do that with weather in the single digits, but I wont be ready to do this tommorow, so it is worth a few calls.

They guys I contracted spayed in between 2x4 rafters on the inside of a 15/12 pitch roof.  They had to dodge knee walls, dormers, collar ties etc.  They did a reasonable job, but if they ask you if a little overspray is OK say NO. They sprayed all over the rafters  >:(.  I can can still see myself scraping the foam off the bottom of the rafters so I could attach drywall in my sleep....or nightmares.

These guys were comercial contractors and actually sprayed the roof of one of the plants from the company I worked at.  They have robots that spray the foam on the outside of the roof to a very even relatively flat surface.  Then they put the EPDM roof down on top of the foam.

I don't know if this would work on a sloped roof.  It would be pretty tricky to get the robot to go up...or down...hill.  Worth a question though I guess.

Tim

[Don P]

We've done a built up or wrap and strap a few times this is one. The ties are not structural, the ridge is a structural 6x16 glulam with 4x10 fohc doug fir rafters on 4' centers with 2x6 syp decking.


This is up top, 2 layers of 2" + 1 layer of 1" for 5" total foam then 2x4 strapping, then 5/8 ply then shingles


This is the ply going on. 18/12 pitch, boy were my ankles glad to get down from there.

[nsmike]

Yes the roof makes sense. Its some where between R28 and R35 given the reference for urethane at R7.1 to R8.7 per inch. the aluminum tape for the seams is to make for a impermeable barrier. The strapping provides an air space that can be vented alllowing for water vapor to escape. Sips might be simpler but this method works. A  friend of mine used a similar system on his cabin where crane access was cost prohibitive.
Mike

[tim1234]

This is up top, 2 layers of 2" + 1 layer of 1" for 5" total foam then 2x4 strapping, then 5/8 ply then shingles

How do you fasten the 2x4's over the 5" of foam?  Loooong screws?  The screws are almost in shear with a 18/12 roof.  Seems like they wouldn't hold the 2x4's very well.

Tim

[StorminN]

Hey Shinnlinger,

We did a stressskin panel timberframe for my uncle's house back in 1990 or so... it's in RI, couple hour drive from you. I'm told it's still doing well, they have lived there ever since. If I remember correctly, those panels were expanded polystyrene with plywood on the outside and gypsum board on the inside... held onto the timber frame with long spikes. Somewhere I have pics...

A friend of mine interviewed for a facilities manager position at a big SIPs panel manufacturer out here. He said the process was very straightforward, very garage-tech, other than their CNC router (to cut the door and window openings)... and very similar to our presses, but bigger... a big press with air bladders and 6psi... they mix up the glue, roll it on with paint rollers, stack the wood / foam up in the press, turn on the air to clamp them, and let them cure. We do a very similar setup for our cores.

I say call Insulfoam or one of the other EPS manufacturers and see if you can buy blanks in the sizes you want, then build your own DanG panels. Most times they will hot wire cut it to the sizes you want, you just have to buy a whole brick's worth.

-Norm.

[moonhill]

Don P. , what are you using for screws?  I realy like that system over SIPs.  Did you need sunglasses while using the foil face foam?  I have only used the urethane foam with a fiberglass reinforced paper face, it's itchy, and factory seconds, and at some cost savings.  I would like to use the foil face stuff though, maybe next job.  I like the idea of only taping the outer layer with staggered under layers, it could save time with a spray can and mess.  As for the steep roof and the screws saging, I wouldnt be overly concerned, but it does cross my mind as well.  Than, I think/try and tear that off by hand or hammer, I bet its stuck on quite well, that's alot of screws.  Where is the calculation for that?  I have also done a straw bale roof with a simular system.  16'x16' cabin with 12/12 pitch roof.  It seen to be doing well 2 years old now and hasn't slid off yet.  And not to be confused with Tim1234, I will place a B. after my name.  Tim B.

[Don P]

There is a stack of wood at the bottom of the roof to make a "dam" for the foam. Then the strapping used long panel screws on 2'centers. Over the rafter bays we used a long enough screw to hit the rafter. On the other straps we had to be careful not to poke thru the 2x decking. In hindsight I should have woven the strapping better. I did attach the strapping together at the peak and ran a simpson metal strap across from side to side on each pair. The engineer did not spec any of that though. Yup sunglasses and sunburn. The only time I've gotten heat sickness was on a roof like that when I was a teenager during summer.  Woke up in the basement, you can get cooked up there.

[shinnlinger]

DonP,

THanks, that is exaclty what I had in mind doing if I went with the built up way.  It is reassuring to know that my idea could work if it comes to that

Norm,

I doubt I will get in the SIPS bussiness, but who knows?

I can get a crane for "free" but now depending on costs it is looking like the mudburn or the DonP method might be the way.

If I was going with ribbed roofing, what do you think If I just threw horizontal strapping every 2 ft on the verticle straping and screwed the steel to that, no sheathing.  Keep in mind I would start this with OSB directly on top of the purlins for racking.

[Don P]

Why not just run the strapping horizontal? There is or could be some venting in the ribs although I think its a moot point with foam anyway.

[shinnlinger]

Don,

I was thining verticly would be easier, but now that I think about, it is probably easier, doing what you suggest, but I was thinking seismic strapping conncting each north and south side strapping over the peak would help hold the whole affair on the roof.

HOw did you connect the foam when you did you operation.  9-10 inch screws are $$$.

[StorminN]

Hey Dave,

No need to get in the SIPs business, but you should check with one of the EPS manufacturers for pricing, even if you're just going to use it as foam board. Here in WA, we are lucky because Insulfoam is right here and you can buy direct. EPS is much cheaper than urethane (blue or pink board).

-Norm.

[Don P]

We used expensive screws and lots of em. I've got another pic around here somewhere I need to dig out. Its one we did some years ago in NC with 4" of foam. We laid the foam horizontally then stood a 2x6 on edge and screwed it through decking to heavy rafters then another horizontal run of foam and another edgewise 2x. We cut the foam so that the 2x's broke correctly for sheet of plywood running up and down the roof. For ventilation we cut a notch in the 2x6's every 4' (If memory serves) that was about 2x6. I would modify that somewhat but it has worked well for them.

Your metal roof is really a big strap. You might want to run straps over the ridge from side to side.

[shinnlinger]

thanks Don,

$$$screws is what I feared I was hoping you had a cheap source for 10" screws.

Norm,

OK tell me more about the EPS, HOw would I find it out this way?  Or could I talk you into testing you greasal suburban on a 3000 mile trip pulling a load?....I'd let you drive my excevator....

[shinnlinger]

Here is an update on this.

I have yet to price sips panels, but would bet it would be more...probably significantly more, but for a Mudburn inspired,  blown in route r-30 on my 2200 ft of roof,  with two layers of sheething and paper and a 10" truss rafter is about $3200 (without roofing and using my already milled materials for the trusses) 

Obviously the most work, but about half ($7000) for a DOn P inspired foam and horizontal strapped r-30 setup.

If I go the mudburn route I can throw ribbed steel on it an be done with the whole deal for less than $6000.