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Architecture/rubber membrane covering flat porch roof

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Expert: - 11/17/2008


Question

Porch roof installed a
Mr. Taylor:

In 1999, I built a new home in Chester, South Carolina.  The house has a 10'deep x 24'long porch on the front.  This roof of this porch is very low-slope (approximately 1/8" per foot)and is covered by a black rubber membrane that resembles a tire tube.  The porch roof is capped by a decorative balustrade that runs the entire perimeter of that roof.

When painting trim and completing other maintenance I noticed that the rubber membrane is NOT attached around the outer perimeter of the roof.  In some places 1" of the OSB decking is exposed.  The decking is wet around the entire perimeter of the roof and is beginning to delaminate.

There is no evidence that the membrane was ever attached to the decking.  Will you respond to the following questions?

1)How should the membrane have been attached? . . . mechanically with some type of flashing around the edges? . . . glued with some type of flashing? . . . other?

2)How should the point at which the roof drains into the gutters been put together? . . .should there have been a drip edge?

3)Do the manufactures of the rubber membranes provide specific, detailed installation instructions that could have been (should have been) followed by my contractor?

4)In your opinion, is my contractor liable for this faulty installation?

During heavy downpours water drains through the porch roof structure.  It drips/pours through the slotted soffit and out of the tops of the column capitals.  Based on the extensive rust appearing on 2 "exterior" ceiling fans and a metal light fixture, I believe water is standing in the space between the porch roof decking and the vinyl ceiling below it.  

I am in the middle of a difficult "conversation" with my building contractor.  He contends the roof was installed properly but has not been maintained.  No instructions for "routine maintenance" were ever provided to me.  Had I known this roofing would last less than 10 years I would have increased the pitch of the porch roof and installed standing seam metal.

A composite photo including photographs of the rubber membrane, of water draining through the porch in a recent storm and the rusted fans and light fixture is attached.

Thanks in advance for your thoughts.

Mike

Answer
Mike - thanks for your question.

Based on the information you've provided it would appear that the installation was improper; it sounds as though the edges were not properly detailed and constructed.

Typically, single-ply membranes are "fully-adhered" and attached at the edge with a metal coping strip that counterflashes the membrane and covers the edge of the decking.  A separate drip edge isn't needed.

Details for installing this product are widely available; Carlisle and Goodrich are two well-known manufacturers and you can find details on their websites, as well as in numerous construction-related publications.  You will also find specific instructions at www.jlconline.com.

I can't make any determination about the cause of the problem in this forum.  You'll need someone to look at it in person.  A home inspector might be able to help.  Does your contractor belong to a remodelor's association?  They might have a complaints board.

You also might contact your local Building Industry Association (find them at www.nahb.org) and see if they have an arbitration group.
    Questioner's Rating
    Rating(1-10)Knowledgeability = 10Clarity of Response = 10Politeness = 10
    CommentThanks for your response and the other sources that I might pursue in verifying the proper installation method. I will definitely follow through on this one.


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Richard Taylor, AIA

Expertise

Ask me about all aspects of house, remodeling. , and room addition design and construction. Ask me about historic homes, renovation, and restoration. Ask me about materials and techniques, and about how you can get the best value for your design and construction dollar. Ask me how you can make your home a very special place. I can't, however, answer specific structural engineering questions in this forum - that's something you'll need on-site observation for.

Experience

I own a full-service residential architectural firm, and have been designing custom homes, remodelings, and room additions across the country since 1983. Check us out at Richard Taylor Architects and RTA Plans. I have written and been published extensively on the subject of residential architecture.

Organizations
American Institute of Architects, City of Dublin Architectural Review Board, Vice Chair of City of Dublin Planning and Zoning Commission, American Planning Association, Board Member Historic Dublin Business Association, Past Editor of SPLASH (a software forum), Past Editor of Open Directory Project, Assistant Scoutmaster, Boy Scouts of America

Publications
Business First of Columbus, Suburban New Publications, About.com, Cleveland Plain Dealer, Columbus Dispatch Residential Architect Custom Home Architect Remodeling Architect

Education/Credentials
Bachelor of Environmental Design (Architecture) Miami University 1983
For more about home design, check out my blog at Sense Of Place and join the conversation on our Facebook Page.

Awards and Honors
2010 Dublin Chamber of Commerce Business Person of the Year

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