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Row House Flat Roof

We just finished these row houses. I’m writing about them because unlike the hundreds we have already done these are more like bathtubs than roofs.

Usually, flat roofed houses have at least one side that is open with parapet walls (parapets are walls that are higher than the roof) on either two or three sides. The slightly pitched roofs usually slope toward the area where the parapet is missing, in place of the parapet there is a gutter to carry all of the rainwater away. These houses have had additions built on where that open area once was.

IMG_0429
Flat roof with ponding water

 

This vinyl sided area you see was built where the roof used to drain into a gutter. A drain was installed on the left side to handle the rain and melting snow. The drain failed during a huge snowstorm and water came into the house on all three levels.

The roof also has a pretty deep depression, when I was done shoveling off the snow I found about three inches of standing water right in the center of the roof; this roof has to fill up with at least 4″ of water before the first drop ever starts to flow into the drain; not cool. Standing water will kill a flat roof in no time. Would you want to get into a tub with 3″ of last nights water in it? Besides being a mosquito day spa, standing water on the roof starts to smell as leaves and debris start to accumulate and it begins to turn into a pond, a pond without a peeing cherub.

Solving the ponding problem:

Tapered insulation is a dense foam 4’x4′ board that has a slope heading in one direction. We use these 4′ square boards in different combinations to add slope to a retrograde roof.

Tapered insulation
Tapered insulation

You can see how the insulation slopes from 1/2″ on the right to 3″ on the left; by the time the insulation is installed across the roof it will be 6″ high; sloping all the way down to 1/2″.

Tapered insulation
Tapered insulation

The insulation is installed and the first course of the White TPO membrane is being installed.

TPO scupper drain
TPO scupper drain

Since this roof has wall all around it I fabricated a scupper drain, the square plate you see is attached to a stainless steel tube, the tube runs through the brick wall to the outside. This is just like the drain in your tub.

Flat roof with ponding water
Flat roof with ponding water

This is the same scupper drain from the back. Its made from TPO coated galvanized steel so we can weld our roofing directly to it. The square tube is made from stainless steel and I solder it to the TPO coated metal. This will pass through the brick parapet wall and carry the water away.

Flat roof before
Flat roof before

Before:

When I took this picture it hadn’t rained for two weeks but the roof still had an inch of water on it.

TPO flat roof with tapered insulation
TPO flat roof with tapered insulation

You can see how the roof pitches directly to the drain, no more pond, no more leaks.

Scupper drain and conductor head
Scupper drain and conductor head

This is where the scupper drain comes through the brick wall, I installed a white aluminum cover plate over the drain tube. Then I installed a conductor head to direct the water down the downspout to the ground.

Here is the other project that we finished the same week:

Before:

Flat roof
Flat roof

This one also failed miserably during a snow storm. Instead of installing a proper flat roof they chose to use a mixture of shingles, flat roof membranes and tar. It worked about as well as you could expect.

During:

New insulation
New insulation

Old roof removed and new insulation installed.

new White TPO flat roof
new White TPO flat roof

New white TPO membrane and new scupper drain installed and ready to face another winter.

TPO scupper drain
TPO scupper drain

My new drain with a plate and conductor head.

Old roof drain
Old roof drain

This was the old drain, the contractor just knocked the bricks out, laid in some bits of metal and tar and called it a day. I was actually surprised it lasted as long as it did.

There are ways to properly address any roof, no matter what the previous owner or roofer did we can always fix it.

If you are having trouble with your roof call me any time.

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