FLAT ROOFS with PONDING WATER
 

SOMAY is frequently asked for a coating that can be applied on a "flat" roof that has "ponding" water (puddles of water after a rainstorm).  A high-performance coating can be used either to solve a current leaking situation or to help preserve a non-leaking roof so that it will not deteriorate and begin to leak. The only appropriate waterproofing coatings for ponding areas on roofs are coatings especially formulated for constant immersion in water, such as a water tank interior coating. SOMAY represents manufacturers of these types of coatings, all of which are solvent-borne coatings.

• • Elastomeric Waterproof Coating
• • Urethane Waterproof Coating To Prevent Bleed Through From Old Asphalt
• • Waterproof Coating That Can Be Applied On Wet Surfaces
• • Coverage Rates
• • Tar & Gravel Surfaces
• • Cautions
• • Comparative Costs Per Square Foot
• • Flat Roof Waterproofing Case Histories
   

SOMAY RUBBER WATERPROOF COATING

SOMAY Rubber Waterproof Coating for Flat Roofs, Product No. 814-01, "Reflective White", a single-component, rubber-copolymer, elastomeric waterproofing sealant and coating for flat roof surfaces.  Has "Energy Star" and UL Class A Fire Rating Certification.  Apply two (2) coats, each at a spreading rate of no more than 70 sq.ft./gal. per coat to develop 10 mils DFT per coat, totaling 20 mils DFT for 2 coats.  Substitute "Polaroof RAC" as the first or prime coat over old asphalt surfaces to prevent tar color "bleed through" It's smart roof maintenance practice to bleach and clean the roof a couple of times each year so dirt does not build up in low spots!

URETHANE COATING TO PREVENT BLEED THROUGH

SOMAY/Andek "Polaroof RAC", (Color: "Aluminum") A single component, moisture-cured urethane, solvent-borne, elastomeric waterproofing sealant and coating for flat roof surfaces constructed of any normally used roofing material.  Approved by Underwriters Laboratories® (UL) and Factory Mutual Research Corporation® (FM).  "Polaroof RAC" is very tough and elastic with high tensile strength and good puncture resistance.  The product contains fire retardant additives and corrosion-inhibiting aluminum flakes for protection against rust and acid rain.  It is ideal as a barrier coat or prime coat over old asphalt surfaces to prevent tar color "bleed through" and discoloration of the "White" color of any finish coating.   Apply two (2) coats, each at a spreading rate of no more than 88 sq.ft./gal. per coat, to develop 15 mils DFT per coat, totaling 30 mils DFT for 2 coats.    After roof application, be sure to keep the roof clean so dirt does not build up in low spots!

WATERPROOF COATING FOR WET SURFACES

SOMAY/Andek "RUBBERKOTE" 1047 (Color: Light Gray), a single component, acrylic polymeric, solvent-borne coating especially engineered as a waterproofing coating for flat roof surfaces which have ponding water following a rainstorm where the use of other coatings will not perform satisfactorily.  Can be applied to damp and wet roof surfaces where curing will occur even underwater, regardless of the thickness applied.  "Rubberkote" 1047 adheres to all common roofing materials, whether horizontal or vertical.  It is ideal for either instant repairs or as a permanent roof coating.  Apply two (2) coats, each at 60 sq.ft./gal. to develop 15 mils DFT per coat, 30 mils DFT for both coats.  Clean Up: Mineral Spirits.  Dry Time: 60 Hours.

COVERAGE RATES

All paint and coating coverage rates are theoretical rates for "smooth, non-porous surfaces" (such as glass).  Rough and/or porous surfaces will reduce spreading rates and require the use of considerably more material.  Furthermore, allowance must be made for less than 100% transfer efficiency. Experienced paint and coating applicators usually calculate a wastage rate of at least 10% for brush or roller applications, and from 20% to 30% wastage rate for spray applications.  This requires the purchase of 10% to 30% or more material than the theoretical amount in order to be sure to apply the proper amount of material to develop the proper minimum dry coating thickness specified (from 15 to 30 mils DFT) uniformly across the entire roof surface for waterproofing purposes. 

TAR & GRAVEL SURFACES

On any tar and gravel surface we recommend that ALL the gravel be removed in order that one has a clean, non-porous, smooth, firm and dry surface on which to apply a coating.  If the gravel is not removed, then one will use many times more material to build a coating film, and risk the possibility that the coating could have voids and not form a satisfactory waterproofing membrane over the entire surface area.  Therefore, SOMAY cannot recommend the application of a paint or coating over any Tar & Gravel surface when the purpose of the coating is to build a waterproofing membrane on top of the roof surface.

CAUTIONS

(1) Proper surface preparation is particularly important when a coating must withstand total immersion under water. 

(2) Old coal tar or asphalt-based roofing materials and/or coatings, including any coating that incorporated a "leafing aluminum" pigment, can be the source of failure due to (a) poor adhesion of the aluminum pigment to the substrate, (b) infirm asphalt surface movement causing the new coating to crack and flake off, (c) moisture entrapment under the old asphalt, or (d) Tar color "bleed through" a lighter color coating applied on top, especially affecting any "white" top coat.

(3) Do NOT apply an epoxy-based or an ethylene-based coating directly over any paint (e.g. over an acrylic "latex" or vinyl/acrylic "latex" paint) that will be affected by a powerful solvent such as mek or xylene, etc. without first applying a protective barrier coating such as SOMAY/Andek "Polaroof R.A.C.", a single component, moisture-cured urethane, as the first or prime coat. 

COMPARATIVE COSTS PER SQUARE FOOT

September 25, 2011

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