WATERPROOFING COATINGS
for
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, a swimming pool coating, etc. SOMAY represents manufacturers of these types of coatings, all of which are solvent-borne coatings, including the following:

1. SOMAY/Carboline "Carbomastic" 90, a Cycloaliphatic Amine Epoxy Mastic, is a high solids, high-build "Aluminum" pigmented coating that cures to a tough, flexible, abrasion resistant film that can withstand mild immersion service such as one encounters with ponding water on a roof surface.  It is a two-component system, Parts A and B being supplied as a Kit with a mix ratio of 1:1.  Apply over a properly prepared, clean, non-porous, smooth, firm, dry surface, at the theoretical rate of 289 sq. ft./gal. per coat, to develop a dry film thickness of 5 mils for each coat.  Recoat in approx. 12 hours.  Apply three (3) coats to develop a 15 mils dry film thickness, thus theoretically using one gal. for every 96 sq. ft. of surface area.  The "Cash & Carry" wholesale price is $739.90/10-gal. Kit, for a material cost of approx. $0.78/sq. ft. for three coats.
    
2. SOMAY/Carboline "Carboguard" 891, a Cycloaliphatic Amine Epoxy Coating, is a high solids, high build coating suitable for constant immersion under water.  It is a two-component system, Parts A and B, supplied as a two-gallon kit, with a mix ratio of 1:1.  Apply to a properly prepared, smooth, non-porous, clean, dry, firm surface at the theoretical rate of 241 sq. ft. per gallon to develop a 5 mil dry film thickness per coat; three coats totaling 15 mils dry film thickness are required for waterproofing purposes, so theoretically one (1) gal. will be used for every 80 sq. ft. of surface area.  Dry time between coats is approx. six hours.  The "Cash & Carry" wholesale price is $729.90/10-gal. kit for a material cost of $0.90 per sq. ft. for three coats.  Ideal for use on roofs from which water is collected in cisterns for drinking purposes.  Has ANSI-NSF Std. 61 approval for use as a potable water tank lining.  Color:  White.
    
3. 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.  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.  At the Factory-Direct, Wholesale, "Cash & Carry" price of $41.99/gal. (in 5's) = 60¢/coat, or $1.20 for 2 coats.  Substitute "Polaroof RAC" as the first or prime coat over old asphalt surfaces to prevent tar color "bleed through" and discoloration of the "White" color of the finish coating. Product No. 814 has "Energy Star" and UL Class A Fire Rating Certification and ENERGY STAR^® Certification.  It's smart roof maintenance practice to clean the roof a couple of times each year.
    
4.  SOMAY/Andek "POLAROOF" N.W., (Color: White – other colors available by special order) A single component, ethylene elastomeric, solvent-borne coating engineered as a waterproofing coating for application to concrete decks, metal roofs, etc., including flat roofs with ponding water following a rainstorm.  Can bridge hairline cracks and tolerate minor movement – has 550% elongation.  Apply two (2) coats, each at a spreading rate of 80 sq.ft./gal. to develop 12 mils dry film thickness per coat, totaling 24 mils DFT for both coats. At a Factory-Direct, Wholesale, "Cash & Carry" Price of $56.99/gal. (in 5's) = $1.42/sq.ft. for 2 coats.  Clean-up: Xylene. Develops rain resistant skin quickly.  Full cure: 24 hours.  Substitute "Polaroof RAC" as the first or prime coat over old asphalt surface.
    
5. 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.  Apply two (2) coats, each at a spreading rate of no more than 100 sq.ft./gal. per coat, to develop 12 mils DFT per coat, totaling 24 mils DFT for 2 coats.  At the Factory-Direct Wholesale "Cash & Carry" Price of $68.99/gal. (in 5's) = $1.38/sq.ft. for 2 coats.  Ideal as a barrier coat or prime coat over old asphalt surfaces to prevent tar color "bleed through" and discoloration of the the "White" color of any finish coating.
    
6.  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.  Adheres to all common roofing materials.  Apply two (2) coats, each at 60 sq.ft./gal. to develop 15 mils DFT per coat, 30 mils DFT for both coats.  At SOMAY's Factory-Direct, Wholesale, Cash & Carry Price of $52.99/gal. (in a 3.5 gal. container) = $1.76 per sq.ft. for 2 coats totaling 30 mils DFT.  Clean Up: Mineral Spirits.  Dry Time: 60 Hours.
    

Coverage Rates (Theoretical vs. Actual)  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 and 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 to the substrate, (B) infirm asphalt surface movement causing the new coating to crack and flake off, (C) moisture entrapment under the old asphalt, (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 (A or B above)  or an ethylene-based coating (D above) 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.

September 1, 2008

                                 COMPARATIVE COSTS PER SQ. FT.
                     SOMAY FLAT ROOF WATERPROOFING SYSTEMS

September 1, 2008