flat roof installation how to help - PeachParts Mercedes-Benz Forum

lutzTD · #1 07-13-2009, 10:28 AM

FLA rainfall is making havoc of my covered patio. the former owner put on a near flat roof with about a 1:12 pitch that is tied into the bottom of the roof pitch and terminates on one side in a 90 degree block wall. the rain is getting in between the block wall and the flat roof and ruining the ceiling of my enclosed patio. It looks like it has rolled out 4 foot wide asphalt. It is flashed on the block wall side but it makes a funny transition where the block wall and the roof pitch meet the high side of the flat roof. anyone know a good resourse for figuring out how to flash this correctly and fix my issue? I am thinking I will rip off the current asphalt and replace it with a EPDM one piece membrane. if I take the membrane up the 90 degree block wall and screww on a edge strip and caulk it I think I can take care of the wall, but what abou tthe corner where the pitched roof, the flat roof and the 90 degree block wall intersect? Any help will be appreciated, I am in a fact finding mode right now. Even if a pay someone to do it I want to know how to do it right first so they cant bull**** me.

thanx

mgburg · #2 07-13-2009, 10:33 AM

Quote:

Originally Posted by lutzTD

FLA rainfall is making havoc of my covered patio. the former owner put on a near flat roof with about a 1:12 pitch that is tied into the bottom of the roof pitch and terminates on one side in a 90 degree block wall. the rain is getting in between the block wall and the flat roof and ruining the ceiling of my enclosed patio. It looks like it has rolled out 4 foot wide asphalt. It is flashed on the block wall side but it makes a funny transition where the block wall and the roof pitch meet the high side of the flat roof. anyone know a good resourse for figuring out how to flash this correctly and fix my issue? I am thinking I will rip off the current asphalt and replace it with a EPDM one piece membrane. if I take the membrane up the 90 degree block wall and screww on a edge strip and caulk it I think I can take care of the wall, but what abou tthe corner where the pitched roof, the flat roof and the 90 degree block wall intersect? Any help will be appreciated, I am in a fact finding mode right now. Even if a pay someone to do it I want to know how to do it right first so they cant bull**** me. ... thanx

Can you shoot some pics so we can see the problem areas?

lutzTD · #3 07-13-2009, 10:36 AM

Quote:

Originally Posted by mgburg

Can you shoot some pics so we can see the problem areas?

pics added, thanx

The Clk Man · #4 07-13-2009, 10:51 AM

I live in Fla for 20 years and had that exact same problem. Heres what you do. Have a rubber torchdown roof installed. I tried everything I knew to do and the roof kept leaking, after the rubber roof was installed it never leaked again. Trust me on this one.

kerry · #5 07-13-2009, 11:17 AM

I agree on the torch down roof, but they're not rubber. They're modified bitumen. The existing roof is not flashed correctly or even at all where it intersects the block wall. Installation instructions that I got when I installed a torch down roof required an angled spacer between the roof and wall, a torch down 'flashing' about a foot wide torched to the roof and wall, and then the final roofing torched on top of the underlying material and to the wall. A metal flashing bolted to the block and caulked on top is then pretty standard but I used roofing cement which has to be renewed every few years.
The existing metal flashing way up on the roof where the space is very small seems reasonable to me as long as the roofing makes the turn up onto the metal.

Brian Carlton · #6 07-13-2009, 11:23 AM

The benefits of proper flashing will be apparent on shingle roofs where the water can run out on the the shingle below the flashing.

On rolled roofs, this benefit is not available and the water will run down the channel that is provided by the flashing. While it runs down the channel, it's free to spread out toward the roof and the flashing would need to be quite wide to prevent it from reaching the deck. This is generally why flat roofs inevitably leak over time. The flashing is just not up to the task.

I also agree that a proper torch down roof would solve this problem. The torch down can be bent up 90 degrees onto the block wall and no water penetration is possible in the joint. To assist with this 90 degree bend, you might ask the contractor to rip a 2 x 4 with a 45 degree angle on the face. This would allow the torch down a transition zone and give it some longevity at the radius of the turn. The contractor will negate this idea and tell you that you don't need it. He's correct if you just want to make the 5 year warranty.

The Clk Man · #7 07-13-2009, 11:24 AM

I stand corrected Sir. all I know is that stuff really works. I owned that house 10 years after I had the Bitumen roof put on and no leaks.

kerry · #8 07-13-2009, 01:02 PM

Quote:

Originally Posted by Brian Carlton

To assist with this 90 degree bend, you might ask the contractor to rip a 2 x 4 with a 45 degree angle on the face. This would allow the torch down a transition zone and give it some longevity at the radius of the turn. The contractor will negate this idea and tell you that you don't need it. He's correct if you just want to make the 5 year warranty.

The supplier of my torch down material sold 4' sections of 45 angle material that seemed to be made out of something like old newspapers compressed. It worked well. The installation instructions required the material, then the fiberglass paper underlayment on top of it, then the 12" torch down material in the transition zone, then the final roof. Been holding up well for 19 years so far.

Brian Carlton · #9 07-13-2009, 01:21 PM

Quote:

Originally Posted by kerry

The supplier of my torch down material sold 4' sections of 45 angle material that seemed to be made out of something like old newspapers compressed. It worked well. The installation instructions required the material, then the fiberglass paper underlayment on top of it, then the 12" torch down material in the transition zone, then the final roof. Been holding up well for 19 years so far.

The usual situation.

The manufacturer knows the proper installation technique and the installer typically ignores it. My own roofer advised that the material can make a 90 degree bend.............

t walgamuth · #10 07-13-2009, 07:54 PM

All of the advice here has been good. I would go a bit further and say that I would take the membrane roof up the block wall, after building it out so that it is all one plane, and wrap it up onto the sloping roof and tuck it under the shingles. All the edges would be welded so that its continuous up about a foot or two under the shingles.

Good luck. If that roll roof had been done correctly it would work fine for a good while. If you used a rubber material to go up and lap under the shingles and ran it out a couple of feet on the roll roof and fully adhered it it would last a good while too.

pawoSD · #11 07-13-2009, 08:45 PM

Wow....that roof design would be a disaster here in MI!

lutzTD · #12 07-14-2009, 08:48 AM

Quote:

Originally Posted by pawoSD

Wow....that roof design would be a disaster here in MI!

no snow here, but we are getting a minimum 1"/day for the last month and a half

lutzTD · #13 07-14-2009, 08:53 AM

I think What I am going to try before I rip it all out is to extend the vally on the top out a little bit and put a kick out flash at the bottom of the wall so the water doesnt curl around and under. I have plenty of water for my testing so I will see pretty fast if it works......

t walgamuth · #14 07-14-2009, 12:56 PM

Flash it with flexible membrane and fully adhere it.