AboutRon Haynes Expertise I can answer questions related to all types of steep slope and low-slope commercial and residential roofing, including asphalt shingles, metal roofing, built-up roofing (tar and gravel), modified bitumen roofing, single ply roof systems, tile, and slate. Questions may relate to design, installation, problem resolution or repair of the roof system.
Experience I have over twenty years experience as a roof consultant dealing with various types of roof systems on commercial, industrial, residential and Government facilities. Experience includes new roof and reroof design, roof repair specification, roof construction, maintenance, failure investigations, performance analysis, inspections, moisture intrusion surveys and studies, and storm damage assessments. I am a registered professional engineer and a Registered Roof Consultant with the Roof Consultants Institute.
Organizations Roof Consultants Institute
Education/Credentials Bachelors Degree in Civil Engineering
Registered Professional Engineer
Registered Roof Consultant, Roof Consultants Institute Certified Infrared Thermographer
Awards and Honors Award Winner, Large Roof Replacement Design Document Competition at the 1999 Roof Consultants Institute International Convention. Dept of Navy Meritorious Civilian Service Award. Armed Forces Civilian Service Medal.
Question Recently I obtained five bids to reroof a flat roof of 2600 sq feet area. The existing roof is tar & gravel and was installed in 1987. The building is in San Diego. It had a small leak last year but after I sealed around the flashing around the nearby vent pipes, the leak seemed to be disappeared.
Contractor #1 inspected the roof and said that my roof is still in good shape and has about 2-3 years life. He proposed to re-seal all vent pipes and exposed nail heads and add gravels on exposed areas. The cost is $1570.
Contractor #2 proposed to re-roof with Dibiten torch down roofing for $10300.
Contractor #3 proposed to reroof with Apex modified bitumen roofing for $8850
Contractor #4 proposed to reroof with hot embeded Polara system for $10750 with 15 yrs warrenty.
Contractor #5 proposed to reroof with tar/gravel for $15,500.
Can you tell me which of the above is a better choice?
Can you tell me which roofing system is more durable than tar/gravel roof? Your reply to these questions will be appreciated. Thank you.
Albert
Answer Albert,
You were wise to get several bids. But you may also need to ask a few more questions of the contractors to understand exactly what they intend to provide. The Dibiten, Apex, and Polara all incorporate a modified bitumen roof membrane covering, but do they include underlying plies? And, if so, are the underlying plies felt paper or modified bitumen plies? How thick is the modified bitumen sheet that will be used? Is the modified bitumen fiberglass reinforced, polyester reinforced, or a combination of the two? Polyester makes for a tougher roof membrane. I like either the polyester or the combination reinforcement. Fiberglass alone is easier to puncture or tear.
I'll go ahead and tell you that Dibiten and Appex are both polyester reinforced and torch applied. But, it is always fun to hear what the contractors say. Actually both are now manufactured and sold by Johns-Manville. If I were picking between Appex and Dibiten, I'd pick the Appex membrane cap sheet. I'm not firsthand familiar with Polara.
It sounds as though you did the earlier repairs to seal the flashing at vent pipes, and this was successful. If this is the case, you could likely save yourself $1570 by resealing once more yourself and put the $1570 toward the new roof, whenever you choose to have it installed. As a repair where the existing roof is exposed without gravel, you could apply an aluminized or elastomeric roof coating available at your local big box home improvement store. You do not have to use gravel. And, of course, if you choose to reroof now, don't bother to do the repairs.
My suggestion would be to make sure you get the details on the roof systems proposed to include how many plies and what type of plies are involved, how the bottom ply will be attached, frequency/spacing of that attachment, and details on any warranty mentioned (i.e., materials only, workmanship coverage, duration, pro-rating, etc.).
You will find that the modified bitumen systems go down with less mess and smell than a tar/gravel system, and for that reason I'd recommend one of the modified bitumen systems.
My recommendation would be to make sure the deck is covered with a cap nailed smooth surface modified bitumen base sheet or heavyweight fiberglass base sheet (such as GAF #75 base sheet) before any ply is torched in place. In any case, I would recommend a base sheet and a minimum 150 mil, or 4.0 mm, thick granule surface modified bitumen cap sheet. If the contractor is installing a ply between the base sheet and cap sheet you could drop this thickness to 120 mils. However, most residential applications incorporate only a base sheet and a cap sheet.
There are also systems where the modified bitumen base sheet is self-adhering. Like a cap nailed base sheet, this helps protect the deck from igniting when the cap sheet is torch applied. In the case of the self-adhered sheet, its adhesion becomes very tenacious when it is heated during torch application of the cap sheet, making for a well "stuck" roof. With a self-adhering sheet, the deck does have to be clean and priming of the deck may be recommended by the manufacturer.
Of note is that I do not believe any of the modified bitumen manufacturer's provide anything more than a limited material warranty for residential applications. So, make sure you know exactly what warranty is being proposed, the limitations on coverage (materials or materials and workmanship), exclusions, etc. If the contractor will not provide at least a 2-year workmanship warranty on his work, I'd look to someone else. I would expect the modified bitumen system to last around 15 years provided it drains well, any debris collection is removed, and barring any unusual weather events
I'm not familiar with pricing on the west coast, but it does appear the $9000-$10,000 cost proposals may be reasonable, depending again on number and type of plies proposed for the roof.
One final note on the modified bitumen roofing choice is that this system can be relatively easily "renewed" as it approaches the end of its service life by applying a quality elastomeric waterproof coating.
