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Thread: Flat Roof (carport) replacement

  1. #1
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    Default Flat Roof (carport) replacement

    Hello folks,

    Long time no post. Looking for some advice / information from those who may have experience. My carport roof is now leaking and it's getting to be a mess (put it off last year and paying the price now). There's no water making it's way into the house as it's flowing "away" from the building. The carport is attached to the side of my 2 story with a "wrap arround" the front (approx 3 feet wide). When we purchased the house, the home inspector did warn me it needed to be repaired / replaced shortly as the roofing material on there was beginning to wrinkle in a bad way. I've been reading arround into various DIY options, i'm not scared in the least tackling this job. I don't want to go the route of the shingle rolls the last homeowner used, laying down felt paper then unrolling that puppy only to perforate it with nails and then tar the seems is what has it in bind already. I'll of course be ripping all existing material off and chucking that to a dumpster, then replacing any plywood sheets which may be weak / damaged over the years or from the water.

    Has anyone arround these parts replaced their flat roof before? What is your preferred method / roofing material? What should i be asking for if i contact a roofing supplier? This going to be an insane job to complete? Not paying huge attention @ the time, I've seen good old Holmes roofing crews rolling out and torching down what appears to be a cousin to the shingle roll. Heating the tar underneath so it adhere directly to the plywood does look like a preferred method to me, with a fire extinguisher on hand or course =) But honestly i don't know really where to begin aside from advice to visit Danforth Roofing Supply. After work this evening i'll post up some pics if it helps out.

  2. #2
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    Ryan

    Default Re: Flat Roof (carport) replacement

    We've just gone through this, as the flat roof on our building started to leak badly. A well reputed roofing crew attempted repairs 4 times, and all 4 attempts failed. We've had leaks all winter now, as they need spring temperatures to do the full replacement. I spoke with our lead carpenter about it, he has been a builder for more years than I've been alive, and he said that that is always the way with flat roofs: once they start leaking, that's it, the only real option is the full replacement.

    And holy expensive too! I heard the price for the job (which will be done soon, thankfully) and it was almost the same as my take home pay!

    For those two reasons a lot of people choose to convert flat roofs to pitched roofs. Just mount trusses on top of the current roof, sheet with plywood, and voila: you now have a normal roof that you can shingle or steel roof yourself easily and cheaply.

  3. #3
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    Default Re: Flat Roof (carport) replacement

    FLAT ROOFING IS NOT TORCHED DIRECTLY TO THE PLYWOOD! That is a 100% guaranteed way to burn your house down, because either the plywood will catch on fire, or the flames will wick through any cracks/openings and catch the inside of the structure on fire. Please don't try that method!

    There are a couple types of roofing: Modbit (basically a 3 foot wide roll of ashpalt similar what you already have), TPO/PVC (plastic), EPDM (rubber)

    I would not recommend doing this yourself. The only true DIY method is the felt/nails/tar from the previous owner. It is failing because it is a crappy method and only hack roofers use it. You might be able to get away with cold applied modbit (spread on an adhesive, lay down your strips of modbit base sheet, spread another layer of adhesive, lay down your cap sheet), but it is not as easy as you think and I can guarantee you will have wrinkles and boot prints everywhere. I don't know how much roof you have, but an average sized garage would take a good experience roofing crew most of the day to tear off and replace. Unless you get unending days of sun, I don't think you can tear off and waterproof in time.

    If I were to get a residential flat roof replaced, I would go with the cold applied modbit method mentioned above. Second to that would be the cold applied EPDM.

  4. #4
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    Steve

    Default Re: Flat Roof (carport) replacement

    I am sorry if I appear to have just fallen off the turnip truck, but I find it hard to believe that you build flat roofs given your annual rainfall and volumes of that white stuff.

    WW
    http://forum.canadianwoodworking.com/image.php?type=sigpic&userid=12450&dateline=127309  6828 Wood Wreck - Structural framing specialist.

  5. #5
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    Bill

    Default Re: Flat Roof (carport) replacement

    They are nowhere as common as pitched roofs for house construction but they do exist. I don't really know for sure but I get the impression a quality flat-roof installation will last a long time - maybe has something to do with the gravel keeping the sun off the materials that degrade.

    billh

  6. #6
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    Default Re: Flat Roof (carport) replacement

    TY for the advice Shaz, appreciate the break down on the types. Converting the rood over to pitch is not an option unfortunatly Callee. On the left at the top of the stairs is a door which walks right out on top of the carport. The carport extends beyond the front of the house about an extra 3 feet. This 3 foot "lip" wraps all arround the front.

    Pic:
    home.jpg

    As you can see in the pic there's an "entry" there @ the front which also is tied into the flat roof....and yes...has a flat roof too, WOOHOO! and yes...it is leaking also. House was build in the 50's, most of the neighbours carports all arround me are pitched with regular shingles. Honestly not much from a DIY concept scares me on replacing this roof. If it takes awhile to "properly" complete it's not a big deal, SWMBO knows i keep 2 weeks vacation on hand per year for reno time. I'll keep digging arround, ty for the info so far folks!

  7. #7
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    Default Re: Flat Roof (carport) replacement

    Another fellow and i applied a rubber membrane EPDM to a medium-size flat porch roof last fall. This product is similar to a thick pool liner, and is available or can be ordered in large sizes to form a seamless roofing surface, or one with few seams depending on dimensions. It is adhered by a special contact adhesive (like contact cement) to the roof deck and seams can be made. This is a cold process, not torched. The deck must be in excellent condition and absolutely clean to get good adhesion and nothing sharp that could puncture the membrane. This product came from SPAR-Marathon in Toronto.. check their website under industrial products/applications.
    This is considered a product for pro installation. Like some other jobs, the installer has to know exactly what they are doing to make a proper, neat and waterproof job that drains and is properly flashed.
    Although if properly installed, this roof could last a very long time, I certainly don't like flat roofs and especially those that can allow standing, pooled water. I would much prefer to see your roof pitched away from your house. This could be easily achieved by making tapered 2x4s and re-sheeting the roof, some of which may be required anyway depending on what you find if/when the old roof material is removed.
    My inclination would be to look for a roofing co that does lots of industrial flat roofs. You could certainly do it yourself with some help but it will be expensive enough that you won't want to screw it up, and you will have no warranty.

  8. #8
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    Default Re: Flat Roof (carport) replacement

    Very nice house Crichton. If you are set on the DIY then the cold applied Modbit or EPDM would be for you. Stay away from any coatings, sprays, or foam. I'm sure you will hear how 'wonderful' they are.

    On the asthetics side of things, Modbit looks like a big long shingle and comes in mostly dark colours (red, green, grey, black, brown...). EPDM is black and looks like a bicycle tire tube (aka not very appealing, but works well). PVC comes in black or white, TPO in any colour.

    Careful of wrinkles or stretched areas, as they will wear faster than the rest of the roof and cause a leak. Make sure your edges are well sealed, and that you have good flashing at your walls (flashing are usually thinner to be easier to work with).

  9. #9
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    Default Re: Flat Roof (carport) replacement

    TY For the info Rick, appreciated! Just trying to wrap my head arround the rubber membrane EPDM and the process for it. Your description for application is great but i'm wondering about the "ballast". Is there another layer which goes over top of the membrane once it's been adhered to the roof or does it come "ballasted"? Hehe seems shaz has answered this before i posted. Was the procedure you did a multi layer applciation? Reading through the catalogue the sizes appear to be fantastic, seriously the whole carport could be seamless.

    General question, i likely am going to have to resheath the roof in a few spots, that's a guarantee. That being said, the pitch of the roof sloping away from the house would not be overly difficult to achieve in light of the mess i'm getting into up there already. Out of curiosity, is there a specific "pitch" / degree / angle used which changes the roofing material used i.e. you go from flat roofing material to shingles? Odd question i know, but curious on it (better to just ask i suppose). If i take this route it's going to be a real big challenge to pull off. I'll post some pics when i get home, As mentioned above, there's a door which walks out onto the carport roof (invaluable when getting larger items upstairs with the help of friends). The base of the door frame sits about an 3/4 of an inch above the roof surface, whatever pitch or slope would be incorporated would (to me maybe i'm out in left field) mean i need to work downward and can't add on top of the existing joists or loose the door functionality / run the risk of water in the house.

  10. #10

    Default Re: Flat Roof (carport) replacement

    Quote Originally Posted by Cricht0n View Post
    TY For the info Rick, appreciated! Just trying to wrap my head arround the rubber membrane EPDM and the process for it. Your description for application is great but i'm wondering about the "ballast". Is there another layer which goes over top of the membrane once it's been adhered to the roof or does it come "ballasted"? Hehe seems shaz has answered this before i posted. Was the procedure you did a multi layer applciation? Reading through the catalogue the sizes appear to be fantastic, seriously the whole carport could be seamless.

    As mentioned above, there's a door which walks out onto the carport roof (invaluable when getting larger items upstairs with the help of friends). The base of the door frame sits about an 3/4 of an inch above the roof surface, whatever pitch or slope would be incorporated would (to me maybe i'm out in left field) mean i need to work downward and can't add on top of the existing joists or loose the door functionality / run the risk of water in the house.
    Could you not cut 3-4" off the bottom of your door and raise the threshold up also?? FWIW.

  11. #11
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    Default Re: Flat Roof (carport) replacement

    Did some digging / reading into the modbit cold applied Shaz, seems like a good system which (from what i've read) gives a shingle like texture as you described above which is the direction i'm aiming for in the end. Seems to be a large debate out there on mobit vs EPDM and their uses. If the EPDM comes out sorta like an inner tube in texture/finish i'll likely shy away from that, but yes i can defintly see the large advantage in that system being that it comes in giant single sheets like a pool liner, with no seams it removes a large portion of the worry.

    And you are right Wally, the apparent is often right in front of me and never seen
    Last edited by Cricht0n; 03-22-2011 at 01:00 PM.

  12. #12
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    Default Re: Flat Roof (carport) replacement

    I believe the point where you go from flat roofing to shingles is 3/12. Even at that point, I would put ice and water shield over the entire area.

  13. #13
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    Default Re: Flat Roof (carport) replacement

    Quote Originally Posted by Woodwreck View Post
    I am sorry if I appear to have just fallen off the turnip truck, but I find it hard to believe that you build flat roofs given your annual rainfall and volumes of that white stuff.

    WW
    Lots of flat roofing going on up here. 95% of commercial are flat roofs. Everyone tries to avoid flat roofs in residential, it's more expensive to build right off the bat, but in some instances there is no getting around it. The best example is if you're doing an addition and there are windows that line in the plane of a pitched rood. There's no way of avoiding a low slope or flat roof in these instances. I would be willing to bet we get better life out of a flat roof up here than you get in cali. It's the sun that kills the roof.

    I agree with the gentleman above who said flat roofing isn't a good choice for DIY. I won't do any roofing of any kind, except for the very smallest projects and I have all the equipment to do it. The rate that roofers charge + the break they get on material + the warrantee provided means that when I want the shingles replaced on my house or shop I call a roofer. If the roof leaks when they're done I call 1-800-get down here and fix my roof and I don't waste a couple of days futzing around with ladders and harnesses.

    Flat roofs I wouldn't dream of doing myself with the exception of the very smallest jobs that no roofer would even respond to. When I do flat roofs I use torch down and I don't recommend doing it without experience. The membrane isn't what's difficult about flat roofing. The details... the flashings, plumbing penetrations, parapet, scuppers ..., this is where it's going to leak and what kills you if you don't know how to deal with them. If that was my roof I'd price a torch down roof. Hot mopped is good on a small roof when there are lots of mech & elec penetrations and EDPM is expensive and that roof isn't a good candidate for ballast because it doesn't have a parapet. Ballast gets cheaper with larger roofs. You pay a premium for a small load of washed stone trucked to the burbs. Even if a torch down roof didn't last as long as an EDPM roof I would bet it would cost you a lot less per year of service to go with torchdown and it would look good on that canopy you have on the front elevation.

  14. #14
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    Default Re: Flat Roof (carport) replacement

    Dave, I do like the hot mopped base and torch down cap method, but I find a lot of roofers won't do it on small jobs... too much liability.

  15. #15
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    Default Re: Flat Roof (carport) replacement

    Quote Originally Posted by shazapple View Post
    Dave, I do like the hot mopped base and torch down cap method, but I find a lot of roofers won't do it on small jobs... too much liability.
    I'm not surprised. I would think it's a business decision. 10 years ago I used to rework Hollow metal doors and frames in commercial and institutional buildings as part of my carpentry service which involves on site welding. My insurer dropped my coverage for that work in 2003. I could have gotten coverage elsewhere but I just dropped that service from the work I do. I would imagine that smaller roofers would be in the same boat.

  16. #16
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    Default Re: Flat Roof (carport) replacement

    TYVM for all the asssitance folks! Off to Danforth Roofing Supply in a couple of weeks once the weather gets a tad warmer, appreciate the details and info it certainly made things alot clearer and hey....i won't end up burning the house down now

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