Flat Roof 3200sq ft insulating

coleimage · 12-01-2005, 06:05 PM

We are about to close on a 2 story, 6400 sq ft, 100 year old brick tobacco barn in NC. This will be used as a photo studio. Currently the building has a "wood deck/ 4-ply builtup membrane and a 90lb. mineral surface cap sheet fully adhered with hot asphalt" ( as described in a roofing evaluation by a contractor ).
view image ( copy & paste if necessary ):
http://www.colerodgerphotographics.c...7_05/roof1.jpg

The roofer advises replacement ( He hasn't specified with what material yet ).

We intended to install insulation between the joists from below ( allowing for ventilation ). The idea was to use a white poly-faced insulation so that we could forgo drywalling the ceiling or installing a drop ceiling. However, given that the roof will be replaced, would anyone suggest it be better to install foam board on top of the deck instead? We would prefer to keep the appearance of the exposed joists while still achieving a an R-31 or better insulation.

Joists image: http://www.colerodgerphotographics.c...10_27_05/1.jpg

At this time, before we begin the project, I would be delighted to hear of any suggestions. As well, we are open to being pointed in the direction of any contractors as well. Thanks in advance. Joe

AaronB · 12-01-2005, 10:04 PM

Thats a nice space.

Spray polyurethane foam roofing will give you the best R value per inch AND a quality roofing system if properly installed. 5" of 3 pound foam will give you just over the R-value you requested.

Is the roof leaking? A 4 ply built up with 90 lb granulated cap is about a 20 year system, and even more if maintained.

To achieve the requested r value with polyisocyanurate insulation, you would need 6" and then a roofing system over the top of it.

You will probably need to seek out a qualified SPF roofer. SPF roofing can be a great system if properly installed, and is easy to foul up if the spray mechanics are not on top of things, so ask for references and CHECK UP ON THEM.

If you were in my area I could install it for around $18-20,000.00 and kill all the birds with one stone and keep your open joists and insulate the heck out of the building and look at this article:

http://http://polythane.com/library/tamu.htm

I hope this helps

coleimage · 12-02-2005, 09:08 AM

Thank you Aaron; a compelling article. I will look for a SPF contractor in the area. Although the price is twice that of BUR replacement, it might very well be justified.
The difficulty, outside of financing this alternative, is finding a qualified roofer.

I'll continue to research this option as well as look forward to more suggestions.

AaronB · 12-02-2005, 02:24 PM

The cost may be twice that of a plain old BUR, but please remember that you are getting all the R value you want, and installing a 100% renewable roof. This means that down the road, your foam roof, if maintained properly, will be able to be re-coated and the warranties extended. Not to mention saving you the ceiling work and still preserving the open joists. When you factor in all the objectives achieved, you have the perfect solution.

Like the articla said...the SPF roofing will pay for itself in short order via controlled climate savings.

coleimage · 12-02-2005, 08:53 PM

There is conflicting information regarding the application of an SPF system over existing BUR. Given that currently, there is negligible leaking, would it be advisable to seal suspect areas, perhaps allow the roof to dry out a season and then apply a SPF system over the existing roof. ( the current roof looks quite good, in fact )

Outside of eliminating tear-off costs, this might be less disruptive ( falling debris/dust in the interior ).

I've read through a fair number of forums where roofing contractors insist on a complete tear-off to achieve satisfactory results for any roof system. However, I encounter an equal number of manufacturers suggesting otherwise.

Thanks, Aaron for you insight. ( I am trying to locate an SPF installer near Durham, NC now.)

joe

AaronB · 12-04-2005, 07:25 AM

Well, Iwould suggest moisture content scans to determine if you have moisture trapped in the roof assembly. If you do, you should remove it. This includes any wet or rotted insulation or decking.

Good roofing practice dictates always repairing a roof before you re-roof, so minor repairs will be routine for the contractor.

One of the nicest things ablout the SPF system is you CAN put it over your current roof, and probably never have to roof it again.

coleimage · 01-09-2006, 11:26 AM

Hell Aaron,

I spoke with a an installer in NC ( ACI ) who applied "Polythane Systems Inc" coatings ( Polythane.com ).
Apparently only 1.5" is customarily applied and to apply 5 or 6 inches would be very expensive ( outrageous was the word ). Can you tell me what system you've applied?
Thank you
Joe

AaronB · 01-09-2006, 01:20 PM

Polythane (now Bay sytems) is the way I am leaning.

I am in the plural component business, but have only dabbled in SPF. I just do not have a need for it on a large scale as of yet.

I do have current pricing though, and have figured a number of about $6.03 a foot with three gallons per square of elastomeric acrylic UV inhibiting coating if you do not have to tear off. This is at 5" R 30-35. North Carolina may not need that much. That pricing is for my company in my area. (Chicagoland)

What if you compare quotes with a tear off and the installation of 4.5 inches of polyisocyanurate board insulation, and a sheet membrane roof applied to that (polyiso board has the same r value per inch)

This would put you WAY over the price I quoted around here. Maybe look around for another company?

You may want to calculate the energy savings and factor that into the equation, also. There have been many many reports of thes systems cutting energy bills in half, meaning the roof starts to pay for itself as soon as you turn that HVAC system on.

justdon · 01-13-2006, 01:32 PM

Whats to prevent you from pitching the roof with lumber and putting 30-40 yr. shingles or standing seam metal on it??? Here in the frozen North of ice snow and changing temps a flat roof is frowned on heavily, yet on commercial (read taxpayers expense )buildings, flat still used alot, and EVERY one of them have problems. Pitch it and forget it!!!

AaronB · 01-13-2006, 03:32 PM

IF you know how to install low slope, there is no need to pitch it. Besides, I bet the project would cost a lot more overall, all factors included.

What do freezing temps and ice and snow have to do with flat roofing failures if the installation was correct? The biggest rpoblem I find in flat roofing is the steep slopers trying to do it.

justdon · 01-18-2006, 11:29 AM

You might(probably) are correct AAron,
I got a bid on a flat roof replace job back in the 80's. Roofer said replace for $XXX and then every two years you MUST swab her down again or I would be back to replacing. The swab every two years was quite high I thought on a per year basis. I backed my truck up to the building, threw up a pile of lumber and commenced to figuring out how to picth is given a 4-12 pitch or thereabouts. Framing lumber and plywood back then was about same price as replacement by roofer. I papered and shingled that and havent been back since. So all those every other year maintance was avoided. I consider it paid for 10 times over, today!!! Just MY story and I am stickin to her!!! Your mileage may vary!!
Now if I had good roofers like YOU around then, maybe not!!
Expansion and contration of the old type asphalt paper and swap jobs here and they didnt last long!!! Have a good one, but would at least look at the option.

AaronB · 01-18-2006, 12:17 PM

Sure, an informed buyer should look at all available options.

I think that roofer was trying to snowball you into bi annual service.