rwolfe

For sure.

RooferX

Hello, our experience and knowledge beyond asphalt roofing is limited, but we are leaning towards pvc for an upcoming project. PVC seems easy to work with and has many benefits. Thanks for the info on Durolast which we were considering. Anyone have any experience with Johns Manville, IB,,Gaf, or Carlisle? Manville is easily available to us at a nearby ABC Supply at about 70 cents a square foot. We are also considering the more expensive Fibertite or Sarnafil pvc roofing.

Also if attempting to go over asphalt roofing, what slip sheet material do you recommend to separate it from the incompatible pvc? synthetic underlayment? Poly sheeting, red rosin paper, or? I like the synthetic but since it would only be acting as a separation barrier over the asphalt and not placed directly over bare plywood, I was leaning towards red rosin paper for keeping costs down.

Thanks for the help guys!

Mike

Tatnic

YOu should check to see how the existing roof is structurally rated before deciding what to do. If its currently overloaded you'll have to remove the asphalt to gain some capacity.

RooferX

Thanks for the response. Yes we have considered the load and was a factor in deciding on PVC which is fairly light (.3 pounds per sq foot). Not to complicate things, but this is for an old warehouse with a very low pitched roof towards one long side and a long gutter. Eventually, he will be doing a tear off when he gets the plans and money. He has a couple of leaks and the roof is very weathered. I was considering a temporary solution by buying used giant billboard pvc wraps that have advertising on 1 side, reflective white on the reverse side. They are 20 x 60 feet (we would use 4 manageable ones even though they have as large as 48 x 96 feet!) at only 8-10 cents a sq foot, can be heat welded or glued like pvc roofing, are uv resistant, and made to last a minimum of five years in harsh weather, but are only 20 mil thick.They weigh 1lb per sq yard, are flame retardant, and mildew resistant. They are much thicker and 7x stronger than traditional tough poly tarps but ony half to a third thickness of pvc roofing products. Later he would have the tear off using that giant tarp in effect as the 45 - 60ml pvc roofing was put in place. I was just trying to save any further damage and give him a low cost good temporary roof until the tear off can be done.But, I don't want it to deteriorate too quickly because of the asphalt against it. I was going to cut and seal the bad spots then lay down red rosin before putting down the pvc billboard tarp. When the tear off comes I was trying to help him in deciding which would be the best for the cost. JM is cheap and convenient as I sated before, but don't know if their pvc roofing has any issues or not and if the added cost is worth the top brands like Fibertite or not.

At that time, new plywood and insulation panels would probably be put down.In cold climates would you bother with top roof panel insulation or just do a fire rated slip sheet and insulate from inside the rafters with R30+ and a 2' air gap for air circulation and condensation issues. Or both? Thanks again for any advice.

rwolfe

The cool thing about PVC is that it is resistent to most chemicals. Especially fibertite. You could consider using a fleece backed pvc and mopping it directly over the existing BUR if it is smooth enough. If not, you can mop a cover board down and adhere a non fleece pvc in place. If your looking to mechanically attach the system, using a cover board is a no brainer.

Regarding jm being cheaper than fibertite. If cheap is what your looking for, GAF has U.L's for Fleece backed tpo mopped with hot asphalt too.
Also, if the warehouse has a metal deck and if cheap was how I needed to go, and most of the time it is, my bid would be a 1/2" high density wood fiberboard insulation mechanically attached and mechanically attach 12 foot sheets of 45 mil TPO down . Easy Peazy. Don't over think this. If the customer needs r-value, add it. No big deal. Just make sure to add the wood blocking at the leading edges. You can squeeze a 15 year NDL out of this system too.

The cool thing about tpo is 10-15 year warranties don't require clad metal at the edges. You can slap down a galvanized edge metal, prime with tpo primer then peel-n-stick 5.5" flashing strip down. Super fast.

Ahhhhh, I love warehouses. Especially metal decked warehouses.

One other thing. If you can overlay the existing, and use the tpo system as noted above, do the owner a favor and possibly set yourself up for a change order. Have an engineer go out and perform a moisture survey so your not going over any wet insulation (if there is any) If there isn't any than no need for it. Moisture survey should run you about 3.50 to 4.50 per square depending on how big the roof is. Also, if your using tpo, put a cheap coverboard on the walls and curbs to divorce the asphalt from the tpo. Nice thing here is you may not have to remove the existing wall flashing if you do this. Also, if using mansville (and some of the others will allow this if the job is big enough and you tell them they need to allow it) you can bag the flashings without a cover board. Flashing height can't be more than 24" though. I don't like doing this as it looks like crap, but if cheap is what your trying to achieve, this technique shouldn't be ignored.

rwolfe

One other thing. Don't hesitate to contact the Manufacturer to discuss these questions. They'll probably tell you the same thing, but atleast you got it from the horses mouth. Whatever you do, red rosin paper or any other slip sheet is not required. Also, I don't think those sheets you stated above are in any of the Major Manufacturer's U.L. listings. Besides, you don't need it if using fleece back anyway.

Tatnic

If you have a low slope roof or flat roof, which many of the old warehouses have, you may have to use tapered polyiso insulation in order to obtain a 2% (1:50) slope. That's considered the minimum slope of flat roofs for ponding reasons. But that's also pretty expensive, so if there's already a 2% or greater slope, then insulating from inside may be better and it does not have to be done simultaneously.

RooferX

Some clarification:

1) we are not going just after the cheapest way, but rather the most cost effective way for the best roof and protection.

2) We have decided on pvc for several reasons but not the brand yet. Yes we are researching each co's recommendations for installation. We want the best value for the money and question any added value vs cost of say LM vs Fibertite and the other brands.

3) we are concerned about the Temporary pvc against the asphalt until he can do a full tear off.

4) We searched different cover boards and do not know if we should go this route with the added costs and if we will be able to reuse them when he does the tear off. Would you do that, rosin paper, nothing, or what for the temporary pvc over the asphalt?

5) while the pitch is low, it's not that low. I think it's about 2 in 40 = 1 in 20. The roof is about 40 wide x 115 long and tilts to one long side.It drops about 2 feet across that 40 wide. The ceilings go from 20 to 18 high roughly.Looks awkward inside, but looks more flat on the roof.

6) It is not insulated inside yet which was gutted and raw. We were thinking to insulate well on the inside and not from the roof side with panels with far lower r value at an added cost. We were suggesting new plywood (or metal?) decking followed by a fire rated slip sheet, then the pvc.

7) Because it is an old flat roof, there are heat trap and moisture problems. We put in 3 turbines for now where there were holes to relieve some of the problem and get some air circulation. If we were to put up a ceiling we are questioning flow even if insulation was backed off 2 inches from the underside of the ply wood.We are looking at possible solutions like Coravent. To further complicate things, 2/3 of the front portion of the building has large wood trusses with 2x8's running lengthwise supporting the roof, while the 1/3 rear has posts and large lengthwise beams 10ft off each wall. 2x8's running the traditional crosswise from wall to each large beam and 2 x 10's notched and dropped over the remaining middle 20 foot span from large beam to large beam . I was thinking maybe hanging the ceiling lower and leveling so it did not slope with the roof and the air space could then be vented. But for now, we are mostly concerned with the pvc roof and the temporary pvc installation.

8)The temporary pvc we are getting off the billboards is NOT fleece backed.

9) We would prefer mechanically attached vs glue/mopped fully adhered for both the temporary and permanent pvc later.

10) I do think a fire rated slip sheet is needed over the plywood before the pvc. Well, so far in my research IB shows this in their videos on their site. But my rosin was just a thought to get cheap protection for the temporary pvc so the asphalt does not deteriorate it. For the permanent install after the tear off we would think a much better fire rated slip sheet over the plywood or a good cover board over insulation panels if we were to insulate on top of the roof.

Thanks again to all for your thoughts and input.

rwolfe

Great response. I didn't see whether or not the existing roof is smooth BUR or Gravel surfaced.

If smooth. You CAN put fibertite over asphalt. Asphalt has no effect on that product. I've never heard of anybody putting a $.77 per foot product down as a temporary solution. Fibertite is a premium product. This doesn't make a lot of sense.

The billboard material idea is interesting and funny. If you go that route, please come back and tell us about the experience. I live and work in Florida, I'd have never thought about that. Course we couldn't do that down here.

I'll tell you this though. As a temporary roof system, I would absolutely put mechanically attached TPO system over a cover board. This is the most cost effective way to install a Temp roof or a permanent roof. Most of the Manufacturer's carry manufactured vents that are pre flashed and can be welded to the tpo. This will help with the moisture problem.

If you are recovering the roof, I'm not sure the fire rated material is required. The existing roof assembly should be fire rated. There is not u.l. which indicates an existing roof over combustible deck, then fire rated material then new roof. Not only that, you said this is a temporary solution, but your planning this job out like it's going to be there a while. No need. TPO over recover board. 2.00-2.25 per s.f. installed. Lovely.

RooferX

Thanks Rwolfe, but I need to clarify more.........

The temporary bilboard pvc is only 8-10cents/ sq ft.

It will be on for at least a year maybe 2 so I am trying to plan as if it would have to last 5 years.

After the tear off, IF we were to use JM pvc, it runs a little over 70 cents a sq ft. at ABC Supply near us.

The recycled billboard pvc's ARE being use in Florida as the best tarps to protect from further rain/wind damage. They are being used around the globe as well. Some users have reported that they handled over 60pmh winds no problem. Think of the abuse many of these billboards in service along the roads of Florida and elsewhere have taken or are taking now.I had to do a bunch of research on a list of possible solutions before coming across these:

http://cgi.ebay.com/20-Mil-20-x-60-V...d=p3911.c0.m14

There's no gravel but the bur has many bubbles, ripples, and alagator cracks.

Couldn't we just mechanically attach the billboard pvc through the old bur and plywood? I guess the cover board would smooth it out for easier installation, but do you think it could it be reused when we do the tear off? But then again he really won't need it later once he does the complete tear off.Thus again I thought maybe just cheap rosin for now. How much does decent cover board cost per sq foot, say the real thin 1/4 inch stuff?

I thought most pvc roofing material were incompatible with asphalt or is the Fibertite you have used felt backed? Once again the final PVC be it JM,IB, Fibertite, or whatever will be put down from new plywood and the bur will be gone when he does the tear off. The existing roof system will be gone and replaced.

It's only the lighter 20 mil billboard temporary pvc, with no felt back, that I question may not last that 1-2 years if it is incompatable with the asphalt. I may have to start calling manufacturers to answer that question, but I thought someone here may know or had experiences laying it directly over old asphalt. We were planning on heat welding prefab flashing pieces from these manufacturers to the billboard pvc to seal it well.

Are you saying you would just go with the tpo (or pvc as in our case) over cover board over the existing old plywood and old bur as a permanant solution?