GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Should I replace rolled roofing on flat roof carport with metal or rubber roofing?

robinrjohn | Posted in General Questions on

My widowed mom was the victim of a sham roofer after some hail damage. A carport my dad built in 1962 had been fine all these years with rolled roofing. Major leaks after shoddy repairs have caused her to have to have some folks give estimates. One man says he will replace it with metal roofing and one says commercial rubber roofing. The first man’s cost is $900 and the 2nd is double that. Is there a general consensus about either of these? Should we assume the man who says “metal” roofing intends to put it over the existing “problem” or that he will take off all the old job that was botched and start fresh. We know absolutely nothing about this. My dad kept it dry for 46 years, but now we are in trouble. Damage is occurring to her little storage area already. Entire carport is leaking. Help!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Michael Maines | | #1

    Robin, is it a low-slope ("flat") roof? If so, your dad probably installed a traditional roof built from layers of tar paper and tar, with a topping of gravel. EPDM ("rubber") is the modern equivalent. I don't think I'd trust a $900 metal roof to hold keep water out, unless there is some slope (about 15°, or a 2:12 pitch). I definitely would not trust either roof without a written scope from the contractor.

  2. wjrobinson | | #2

    Mopped on silver glass filled goo, years ago on low slope leaky roll roof, no leaky now. Lowest cost. Rubber roof is good choice too at high end. Budget rules.

  3. davidmeiland | | #3

    $900 for a metal roof is quite low unless it's small, but a simple shed shaped carport might be that cheap and easy to install. Mike, your pitch figures are conflicting, 2:12 is about 10 degrees and I would want 3:12 or about 14 degrees for most metal roofs. Robin, can you post a pic of the carport?

  4. robinrjohn | | #4

    Thanks so much for your information. I'm afraid I don't have a picture on hand and my mom is several hours from me. I honestly don't know if there's any slope, but the roof appears flat. Small carport, with room for one car underneath and storage room attached; whole thing around 13 X 25 ft. (rough guess), but no room to spare with a car underneath. Another question: Is it to be expected that a metal roof will be installed over the roof as it now exists?I believe that's what the 1st roofer intends. The 2nd roofer( who wants to put the rubber roof on it) says someone put nails in the rolled roofing which shouldn't be there. Is it ever ok to install a new roof over an existing one? My mom really can't afford the 1800. that the 2nd roofer wants for the rubber one. My dad always kept rolled roofing on it, with edges hanging over a bit on all sides. Wasn't fancy, but it never leaked....since 1962! I've got a 3rd man coming to look at it in a few days.

  5. robinrjohn | | #5

    Oh! ....and AJ Builder, thanks. Budget definitely rules here. Tell me more about mopped on silver glass filled goo.

  6. wjrobinson | | #6

    One brand at Home Depot. Gardner premium aluma fiber reinforced roof coating.

    Home depot $80/4.75gallons.

  7. davidmeiland | | #7

    Appears flat? No metal roof.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |