What are the low cost roofing options that can be applied over a SIP roof? What is required to install each option?

Specifically, I am interested in options for a very low pitch / flat roof in a cold climate (Connecticut).

I saw this and found it interesting:

Spray Foam:
http://www.sprayfoam.com/spps/ahpg.cfm?spgid=7

Would it be a good option? How would it be applied to a SIP roof - would you add another layer of OSB before you sprayed the roof?

What are the low cost alternatives? Rubber? Corrugated metal? Asphalt shingles? And approx. TOTAL cost per sq foot.

For corrugated metal or standing seam would you use roofing felt (tyvek?), horizontal and vertical furring strips, and then the roof? or would it be fine to place the roof directly over the felt? Is there and metal roofing option that due to its profile creates an airspace under the roof without the need for furring strips?

Yes, Chris, I know that with Steel SIPS you can leave the roof exposed and I am considering that option. I just want to compile a thorough list of the options that can be used with an OSB roof with associated costs, installation overview, and positive and negative attributes.

If people write all the information that they know about all of these options, I will try to compile it into a solid reference article.

If you have time could you fill out the following for any roofing option that you are familiar with:

ROOF TYPE:______________________________________________

INSTALLATION OVERVIEW OVER OSB SIP:_____________________

TOTAL COST OF INSTALLATION - MATERIALS AND LABOR:_______

INTERNET REFERENCES / PRODUCT SOURCES:__________________

COMMENTS:_______________________________________________

are you talking 1/4" per foot or ?

Torch down roofing with base sheet is about $3.25 L&M probably the least expensive

	Modified bitumen or “torch-down” roofing got its name from the installation process which done by torching the sheets in the overlap area. Is like a large rubber sheet that’s actually vulcanized onto a fiberglass base sheet. Highly recommended for most flat roofs, torch down roofing is similar to the tar and gravel roof. This roof adds layers of polyester or fiberglass with bitumen to the standard tar and gravel layering system.

http://www.gaf.com/General/GafMain.asp?Silo=COMM&WS=GAF&App=ROOF&Force=../../../../Content/GAF/COMM/ROOF/COMM_learnabout.asp%3fWS=GAF%26Silo=COMM%26App=ROOF%26Uid=

Between 1/4" per foot and 1" per foot.

Please comment on the following entries... I will integrate your comments. Please feel free to add an entry.

ROOF TYPE:
Spray Foam

INSTALLATION OVERVIEW OVER OSB SIP:
You should be able to go over the SIP panel. I would use a primer to enhance adhesion and minimize water absorption in the OSB.

My only hesitation would be if there was significant movement of the SIPS panels. If you observe a lot of movement an overlay may be advisable.
As always ask you supplier for their written recommendation.

TOTAL COST OF INSTALLATION - MATERIALS AND LABOR:
Roughly $250 a square in most places in the country

INTERNET REFERENCES / PRODUCT SOURCES:
http://sprayfoam.com
http://www.dura-foam.com/foam-roof-system/installation-process/roof-preparation/

COMMENTS:
Whenever possible, spray the foam directrly to the decking or at least to a cover board that is securely attached to the decking. Remember most leaks on a SPF roof come from improper edge flashing and through roof penetrations that have become cracked or improperly flashed.

Properly installed and maintained, you should not have to replace the foam roof. It needs to be recoated typically every 10 to 15 years depending on the type of coating and the environment.

Adds R-Value.

Can be used on a nearly flat roof.

ROOF TYPE:
Two Layer Modified bitumen or “torch-down” roofing

INSTALLATION OVERVIEW OVER OSB SIP:
Tyvek Roof. Fasten fiberglass substrate over Tyvek with screws. Lay bitumen layer over fiberglass sheets. Use torch to 'melt' bitumen layer and bond it with the fiberglass layer.

TOTAL COST OF INSTALLATION - MATERIALS AND LABOR:
Roughly $325 a square.

INTERNET REFERENCES / PRODUCT SOURCES:
http://www.gaf.com/General/GafMain.asp?Silo=COMM&WS=GAF&App=ROOF&Force=../../../../Content/GAF/COMM/ROOF/COMM_learnabout.asp%3fWS=GAF%26Silo=COMM%26App=ROOF%26Uid=

COMMENTS:
Can be used on a nearly flat roof.

Difficult for DIY

didn't know it neded to be geared for DIY, GAF also make a similar product in a peel-n-stick

Chris - it does not have to be geared towards DIY, The foam roof also is not a DIY job, actually, it is even harder.

I am hoping that people with experience with different types of installs will throw in information and we can create a bit of a resource on roof / siding (other thread).

tlynch,

I was recently at Oak Ridge National Laboratories and one of the leading residential building scientists mentioned problems with open cell foams being used under metal roofing. The temperature build-up can cause open cell foam products including EPS to be compromised and potentially melt. This may not be as big of a problem in CT, but all others on this board considering metal roofs over EPS or other open cell foams sprayed into the roof deck should be cautious. Of course, he said that using a reflective coating on the metal roof and or a radiant barrier will help, but why not just use PUR sips for the roof as this negates the concern.

We have never seen it get "that hot" in Florida even when installing black shingles directly to EPS panels

In a hot climate I think a ventilated roof makes a lot of sense, not just to be easy on the materials but also for energy efficiency.  By ventilated roof I don't mean ventilated attic -- I mean a sealed, insulated attic, but with the roofing furred out leaving a small air space between the sheathing and the SIPs roof.  This is also good for moisture control, as anything that gets through the sheathing has another chance to drain/evaporate away before it gets into the roof itself.  Of course, we're talking about low cost roofing options, and this is a more expensive option.

I just replaced some damages shingles on my own steel SIP roof this week caused by a falling tree, shingles attached directly to the steel skin, panels were as clean as the day installed, fasteners showed absolutly no signs of rust or corrosion. The steel skin panels are also the secondary water barrier, unlike OSB.
The shingles are for cosmetic purposes only

Chris,

I plan another visit to ORNL this spring to investigate their comments/findings further and will share at that time.

rnortman--what type of sheathing are you recommending on top of the SIPS furred out? What's your impression of the ZIP system as the outer skin of a SIP roof panel?

thanks!

chris,

how do you seal the seams on your metal roof panels?

First of all, I just realized that I used the term "sheathing" in my post, where I really meant "cladding".  So I'm not sure which question you are asking, but I'll answer both: For the cladding, I am thinking of any of the "normal" residential roof options -- shingles, standing seam metal, slate/tile, etc.  Any of them can benefit from having a ventilated, drained gap underneath them.  The details vary with the type of cladding.  As for sheathing, you may or may not need an extra sheathing layer -- some of the standing seam metal claddings can be attached directly over furring strips, with no additional sheathing.  (There are, I have heard, some horizontal furring strips with drainage holes in them for this purpose.)  Aside from that case, though, you'll have vertical furring strips and then a layer of OSB sheathing.  I would put tyvek/felt underneath the furring strips to protect the SIPs, and then another wrap over the extra sheathing to protect that.  (Though really, it may be able to dry pretty well on its own and it isn't structural anyway, so if you're feeling lucky and aren't in a wet climate perhaps you could get by without it.)

I don't have experience with the ZIP system; obviously you wouldn't need a wrap if you were using that.

CTP;

there is no need to seal the roof panel unless they are to be left exposed as the finished roof, then you would use a pressure sensitive roof tape

Mortman,

Vented horizontal furring strips are available.  I saw them installed in Florida under roofs to let the water drain.  At this time I can not remember the brand name or company.

Would anyone consider laying a roof over OSB SIPS without furring strips?

Has anyone done this?

Yes,  I have done it. Why wouldn't you?

I am scared that the OSBs will absorb moisture and not be allowed to dry properly, and I will end up having a major structural problem. Especially in a flat roof situation.

I own a Boston Whaler which is a a boat made with thin fiberglass skins filled with foam, they call it unibond construction. Although my boat is 25 years old and is still unsinkable and very solid, I have seen that water will eventually find its way through anything, no matter what precautions you take. And in a foam sandwich construction method, it is very difficult to repair the skins of the sandwich.

Then you have made the case for steel that does not obsorb moisture