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EPDM rubber roof installation and repair details (C) Daniel Friedman Eric galowEPDM Rubber Roof Coating for Repair, Life Extension, Color Change
EPDM roof coatings

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EPDM rubber roof coating information:

Special coatings for EPDM roofs using silicone, latex, or acrylic paints or sealants are provided by a number of manufacturers. These EPDM coating products may be described as intended to extend the EPDM roof life, seal EPDM roof leaks, or change the EPDM roof color to improve building cooling costs.

This article series describes the properties of EPDM roofing, EPDM roof installation, inspection & repair. An EPDM roof installation study & roof repair history spanning fourteen years, from original rubber roof installation (and the mistakes & shortcuts that led to leaks and trouble) to an extensive tear-off and re-roof repair that was made along the entire problem roof's lower edge



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Use of Coatings for EPDM Roof Repair or Life Extension

EPDM rubber roof installation and repair details (C) Daniel Friedman Eric galow

[Click to enlarge any image] Shown here, a worker is applying adhesive cement prior to gluing down an EPDM roof patch. But what about simply spraying, pouring, or painting on a roof coating to extend the life of an EPDM roof? Is it necessary? Are EPDM roof coatings recommended by the EPDM roofing industry?

A number of companies provide several types of coatings that are used for sealing or repairing flat and low slope roofs originally covered by an EPDM membrane.

Separately at EPDM, RUBBER, PVC ROOFING we define EPDM, describe its properties, and discuss its typical life and warranty periods.

Reader Question:

Can you tell me where in surrey or white rock , bc one can get liquid roofing to redo over a epdm roof and what products are ok .
Is Gaco elastomeric ok ? anything else ?
Thanks
R.B. - by private email 2016/05/11 - Surrey B.C.

Reply:

According to the EPDM Roofing Association, no special coating or surface treatment is required. Howerver quite a few roof coatings are sold for application on EPDM roofs including silicone (Gaco's product about which you asked), acrylic, and even latex.

Some of these coatings have a primary purpose of changing the roof color to a light one to reduce buiding cooling costs. Others might promise repair of a leaky EPDM roof or an extension of the roof life. For example, Gaco says [paraphrasing] "two coats and you're good for 50 years". Indeed silicone is a time-tested sealant that in my experience is durable.

OPINION: Any coating is going to be much thinner than the original EPDM, and subject to the same stresses as the original roof. Coatings may be pretty effective on worn surfaces of some roofing materials, but less-so on bridging cracks, gaps, tears, and still less so applied over EPDM that has water below. And don't confuse a coating intended to change the roof color as a coating expected to fix roof leaks.

I have not had good luck with simple add-on coatings on roofs; ultimately the forces that caused a crack or tear in the original roof seem to work on the coating too. I have had good luck with cleaning the area of roof damage then gluing down (contact cement) an EPDM patch over the damage, then sealing the edges of the patch with EPDM seam sealer or even black silicone.

https://gaco.com/product-details/gacoroof-100-silicone-roof-coating/ has a number of resources. You'll read that the company produces membranes and coatings used in challenging environments including spray coatings on foam insulation, underground liners, and cistern liners. You'll also read that properly installed the coatings are not a trivial application; there are adhesion testing, a requirement for surface cleaning and priming (not always required), temperature concerns, moisture concerns, pinholes in coatings, and other snafus to avoid.

Let's take just one roof wear-stress factor: the tensile strength of the roof coating - its resistance to tearing under various effects:

http://www.epdmroofs.org/attachments/2004_03_epdmrevisited_rci_trial.pdf is a study worth reading from which I excerpt:

The tensile strength for ballasted membranes ranged from 10.8 - 14.9 MPa (1560 2160 psi) (Figure 1) and from 9.4 - 13.5 MPa (1350 - 1950 psi) for exposed membranes (see Figure 2). The ASTM D 4637 minimum requirement for new sheet is 9.0 MPa (1305 psi) and 8.3 MPa (1205 psi) for heat aged samples. MRCA ME-20 requires new membranes to meet a minimum of 6.0 MPa (850 psi), and 5.5 MPa (800 psi) for aged membranes.

Now over at GacoFlex-S20 product specs
https://41z32e1503dj3gyqe3151089-wpengine.netdna-ssl.com/wp-content/uploads/PDS-GacoFlex-S20.pdf

We read Tensile Strength @ 73˚F D412 450 psi 150 min for this product.

OPINION: I am not an expert on EPDM / roof coating tensile strength testing but it looks to me as if 450 psi is a lot less than 1350 psi - the lowest tensile strength for exposed EPDM.

That data seems to support patching rather than spraying for the longest duration EPDM roof life; particularly for smaller residential roofs where the leak issues in EPDM are at flashings or seams, repair may be a better course of action than spray coatings. Coatings, on the other hand, may be a reasonable approach to extending the life of a worn roofing membrane that is suspected of pinhole or crack or oxidation or weathering problems.

A bit of research on EPDM roof coatings found information I cite below and also the observation that most of the research on "performance of EPDM roof coatings" seems focused on the advantages of adjusting roof color or reflectance to create a high-albedo roof in urban climates.

I'd give Gaco technical support a call to ask about the applicability of their coating system to your particular roof. Also be sure to review the roof coating warranty details and the installation procedures and specifications since failure to follow the manufacturer's instructions may not give very nice results.

To look at more EPDM coatings contact one of the EPDM coating specialty suppliers such as epdmcoatings.com (in the U.S.).

References on EPDM Repair & Coatings

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