Replies

1. 
   Scooter1 | Sep 16, 2002 03:45am | #1

   Flat Roofs are a b i t c h ain't they?

   Old school approach is a hot mop, 3-5 layers of 30 lb felt and hot tar. Messy but fairly simplistic. Average life span is about 10 years.

   EPDM is a great product but it is not applied by torching on. It is a peel and stick product. I think you got "torch on roofing" which, quite frankly, is not as good as hot mop and not nearly as good as EPDM. Average life span of EPDM could be 15-20 years on a flat roof.

   Torch on roofing is a rolled product with lotsa seams which is applied by applying a hot propane torch to the underside and stomping it in place. I wouldn't use it except for outbuildings or sheds. I wouldn't put it on any structure that is remotely important.

   Rather than look for an architect, I would contact a competent commercial roofing company, with a track record and a warranty to back them up. Ask for referrals and call the sources. Ask for their recommendation as to specific product for you and get prices on a square foot or "square" basis. Get some other quotes and compare prices on a square to square basis. Go with the one you feel is the most compentent.

   Regards,

   Boris

   "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927

1. 
   Framer87 | Sep 16, 2002 04:07am | #2

   Dear Mr. Yeltsin,

   Thanks for the advice, can you tell me what EPDM stands for?

   Framer87

2. 
   Piffin | Sep 16, 2002 04:49am | #4

   Boris, I hope I don't step on too many of your toes here but I wanted to modify a few of your statements. I agree wholeheartedly with your final advice tho'.

   Built up roofs are done with layers of 15# felt iembedded in hot asphalt. I did it for about fifteen years and never saw one that used 30# on site or in any of the spec books. The number of plies is an indication of life expectancy. A well done three ply will last fifteen years, except in extreme climates. A five ply (usually only on govt spec jobs) might last 25 years.

   Modified bitumen single ply roofing is applied with a torch, eliminating the need for dangerous and expensive tar kettles on certain jobs. Unfoirtunately, the arrival of modified (nicknamed torch-down rubber - a misnomer) made it relatively easy for underqualified, under equipped persons to compete in the flat roof arena. This is primarily responsible for the bad rep it has gotten - too many amatures applying it. It is possible to apply a thirty year roof (extended by recoating to protect from UV rays every five years) with modified but it's not my material of choice. Main reason is that single ply roofing is weakest at the seams, which are only four inches so the slightest error can cause failure.

   There are two thicknesses of EPDM (ethyl propyl dien monimer - I think) so it is possible to have a fourty year roof with it. I have never seen it as a peel and stick product though, but that doesn't mean it isn't made that way. The look and feel of it is just like a rubber inner tube. It is usually applied with contact cement in residential applications. It can be stitched down with metal at the perimeter and ballasted with large smooth river rock about 1-1/2" diameter. The ballast protects from UV rays and holds in place against wind. It also sees some installations with mechanical means on commercial roofs.

   Framer87,

   If you want a super good roof, find a reputable roofing company to advise and install one of these roofs. The EPDM is by far the best unless there will be a lot of traffic on it.

   but another consideration - if the modified you have is only a few years old, it has not worn out yet, possibly. You mention large air units. I am willing to bet that when the previous roofer did his work, he tryed to work around them without removing them and failed to flash against them adequately. He saved himself some work and brought you up short. If my instinct here is right, you have a fifty/fifty chance that some repairs by a knowledgeable person to fix that job will see you through several more years. Have a few different companies check it out until you feel comfortable following your instincts on it. Ask around for references first and you might even get the right guy the first time.

   Good luck.

   Excellence is its own reward!

1. 
   CloudHidden | Sep 16, 2002 05:27am | #5

   One I've heard of recently is the Dow Corning 3-5000 system......1" polyurethane foam sprayed with an automated gun, coated with a silicone roof coating and covered with 3M roofing granules. Guy I know just got a big contract to redo some school roofs in SC.

2. 
   Framer87 | Sep 16, 2002 05:59am | #6

   Piffin,

   Thanks for your informative response to my posting.  How big a deal is it to disconnect my heating units?  The roofers who have come out to look at my job all recommended tearing off the existing roof and starting from scratch, and if that is done the units have to be moved.  Framer87

1. 
   Piffin | Sep 16, 2002 06:17am | #7

   For big ones like that, you need a crane and an electrician standing by. IMOExcellence is its own reward!

1. 
   Framer87 | Sep 16, 2002 03:47pm | #11

   One of the roofers who looked at my job said to disconnect the units, and his men would jockey them around.  Will this damage the new roof?

2. 
   Piffin | Sep 16, 2002 04:56pm | #15

   He has seen the units and knows how strong his men are. No problem with damaging the roof, they'll use some cushion or dunnage to set it off onto.

   It sounds like he is the roofer you want, if he is the only one willing to work the flashings and air units properly. Roofers looking to save this step might have the frame of mind that other shortcuts are acceptable too.Excellence is its own reward!

3. 
   GregGibson | Sep 16, 2002 09:37pm | #16

   I don't know guys . . . "small commercial building" ? ?

   When I see "flat roof" I immediately start to think about how to put a slope on it. You need to analyse how long you intend to own this building and look at the possibility of standing seam metal with a slope. The cost might be higher than a re-roof, but future problems would be addressed.

   Might be time to think outside the box.

   Greg.

4. 
   Framer87 | Sep 17, 2002 03:10am | #17

   Greg,

   What is standing seam metal?  Is it possible to mount my heating units on it, there is nowhere else to go with them?  I agree with the slope idea.  What happens to the edges of the roof?  and what about drains?  Thanks for your help-framer87

5. 
   GregGibson | Sep 21, 2002 12:35am | #19

   Sorry, mate, I've been away.

   Standing seam is .... well, think of the "V-crimp tin" or galvanized

   metal barn roofs you've seen. Quality of material, color, everything

   varies from product to product. I'm in Southern Georgia, so snow load

   will NEVER be a concern. I've seen flat roofs sloped with steel frames and with wood, both trusses and rafters.

   Your treatment of the heat and air units is up to you - platforms standing proud of the roof usually work. This need not be a terrible expensive roof system, depending on the size of the building. As I said, consider how long the roof is going to be YOUR problem. If I were going to own the building for very many years, I'd go for it.

   Greg.

   Edited 9/20/2002 5:49:25 PM ET by Greg Gibson

2. 
   G80104 | Sep 16, 2002 06:32am | #9

   Framer87,

                  EPDM  is Ethylene Propylene Diene Monormer Firestone is one of the better makers of this product. As Piffin stated it is put down with glue, Flashing & edge seal is the part that makes or breaks the job. Try Google.com for a search on the subject, I am sure you will find more information then you want!

3. 
   TLRice | Sep 16, 2002 04:00pm | #12

   I use rooftop-mounted HVAC equipment frequently, and assuming that yours are properly installed on a decent curb, should not require removal for re-roofing. The curbs sit directly on the structural decking and are insulated and roofed over, roofing materail/membrane up the side of the curb and overlapped with counter flashing at the top of the curb. The counterflashing, if not severly corroded can be bent up to accomodate new roofing material and the bent back into place.

   Once you get a roofing contractor, go up on the roof and look at the equipment curbs/flashing and ask them how they will deal with them.

   Never seen units removed for re-roofing, but if you have to, depending on what the units are, you will have a gas line to remove (which might have to be removed to re-roof any way, depending on the routing), an electrical supply, a supply and a return duct (these may be attached directly to the curb and not the unit).

3. 
   UncleDunc | Sep 16, 2002 06:24am | #8

   Piffin,

   Well, I'd probably use 4" rock, but that's just because I live near Rocky Flats, where little rocks have been known to jump up out of the ditch on windy days and make golf ball size dents in car doors.

   And then there's the next mesa south of there, where the railroad tracks make a big loop before they start up the mountain. They got tired of the train blowing off the track there, so now there's a string of about a dozen hopper cars full of rock permanently parked along the west side of the main line to block the wind.

1. 
   Piffin | Sep 16, 2002 06:43am | #10

   I know what you mean. Some days, the giant sneezes. I was coming down the hill near Evergreen one day when the Airstream being pulled at seventy MPH aways in front of me got picked right up and set down in the next lane and continued swaying until the driver could get stopped to clean out his drawers.Excellence is its own reward!

1. 
   heck22 | Sep 16, 2002 04:10pm | #13

   Sidebar to piffin,if you don't mind:Have you any experience with elastomeric roofing such as Conklin's 'Rapid Roof'?

   If so, what's your opinion of these types of products for flat roofs?

   jwwhat the heck was I thinking?

2. 
   Piffin | Sep 16, 2002 04:49pm | #14

   No expeience, no opinion.

   Interested in learning more if someone were to start a thread entitled, "Elastomeric roofing"Excellence is its own reward!

2. 
   Scooter1 | Sep 16, 2002 04:14am | #3

   I have no idea. But it is a rubber type product which is applied by peeling off a protective paper layer and and it self sticks. It also self seals too. There are lotsa articles on it, and application techniques in both FineHomebuilding and Journal of Light Construction.

   Regards,

   Boris

   "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927

3. 
   pkuniacke | Sep 17, 2002 06:16am | #18

   Framer87,

   I am an Architect who does 2-3 re-roof projects a year (commercial, public, etc.) and have used most major roofing systems/manufacturers over the last 14 years.  Flat roofs as it has been stated, will leak regardless of roofing system.  You will need to have at least 1/8" per foot of slope to get the water going towards gutters/drains.  It helps to design 1/4" per foot slope minimum because the installation usually falls short of expectations in places.  The best way (expensive) is to put a truly sloped roof over your flat one which will probably inprove the look of your structure.  Many small and large facilities do this with traditional framing or light weight aluminum trusses designed specifically for this purpose (they look like large awning structures). 

   All things being equal I would specify a 3-ply modified SBS or 4-ply built-up roof.  Normally for a building like yours, I would go with a single-ply rubber, but significant bird droppings are known to break down the material.  Built-up roof manufacturers are in order (best to worst) Tremco, Garland, Soprema.

   Whatever you do, know these things:

   -  the roof warranty is barely worth the paper it written on regardless of manufacturer.

   -  The installer is everything.  If you use a large outfit, make sure you get his "A" crew, and not the idiots.

   -  Do not accept "ponding" on a newly installed roof.  There should be enough slope for all water to drain off within 24 hours.  Roofing manufacturers will allow this in their warranty, but this is no good.  Remember the standing water location if you accept such an installation, because that is where you can later direct the repair crew.

   -  All rooftop HVAC equipment should be boomed up a foot or so to facilitate proper flashing (if curbed) or installation (if just sitting on P.T. sleds).  This is assuming you are keeping the RTU's for a few more years.