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Model # RC905-2

Internet # 202086637

Store SKU # 548821

5 Gal. Ultra-Siliconizer Roof Sealer

This item has been discontinued.
The Home Depot no longer carries this specific product.




Model # RC905-2

Internet # 202086637

Store SKU # 548821

This product is a single component 100% acrylic silicone sealer for roofs and walls with outstanding adhesive properties that will provide a thick, high performance, water and weather resistant seal on most surfaces, usually without need of a primer coating. Due to a transition process, Lanco Ultra-Siliconizer normally dries in half the time as other similar products, ensuring a quick and effective installation. It will significantly lower the interior temperature of the structure by reflecting 78% of the suns’ rays and reducing heat received by 90%. This revolutionary technology allows the finish to remain whiter than similar products on the market, maintaining an average solar reflectance of 84% three (3) years after application (as independently tested ASTM C 1549). This ensures a long-term advantage over similar products on the market. Product will not crack, peel or blister even under severe weather conditions when applied per manufacturer’s specifications.

  • Waterproof for immediate repelling of water
  • For waterproofing and protecting a wide assortment of commercial and residential roofs approved roofing systems and/or substrates that are structurally sound and in good condition
  • Applies light blue, dries ultra white
  • Product must be applied at 50 sq. ft. per Gal. in at least 2 coats 24 hours apart for a minimum film thickness of 32 mils dry (About the thickness of 12 sheets of paper)
  • 2-4 hours drying time
  • Cure time is controlled by thickness of the applied coating, relative humidity and temperature
  • Allow 24 hours dry time between coats
  • 100% acrylic/silicone technology

Info & Guides

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Product Depth (in.) 
Product Height (in.) 
Product Width (in.) 
Coating Base 
Coating Consistency 
Color Family 
Commercial / Residential 
Commercial / Residential 
Container type 
Dry Time 
Fire Rating 
Class A (over non-combustible substrate) 
Roofing Product Type 
Roof Coating 
Surface Recommended 
Protects and waterproofs a wide variety of approved roofing systems and/or substrates, including conventional bituminous built-up roofs, asphalt, aged metal, EPDM (Rubber), polyurethane foam, concrete, and asphalt shingle roofs. 
Warranty / Certifications
ENERGY STAR Certified 
Manufacturer Warranty 
Lanco warrants only that this product is free of defects, since many factors which affects the results obtained from this product (such as weather, workmanship, equipment used and prior conditions of substrate) are beyond our control. We will replace at no charge any product proven to be defective within 10 years of purchase, provided it has been applied per manufacturer’s specifications. 


Rated 4.3 out of 5 by 16 reviewers.
Rated 5.0 out of 5.0 by AWESOME Product! Works Great I installed this product in April 2015. Installation was quick and easy. Clean up was also easy and quick. I used a total of 9 five gallon buckets. How well did it work. It has been working flawlessly. It has sealed the roof well. It also prevents heat gain very well. I took Thermo pictures of the roof prior to starting and then after the two coats were applied. The results were very positive. Over a 60 degree surface temperature drop. I attached a report of the surface temperature difference. This is a very good product. I will follow up in two years. July 22, 2015
Rated 5.0 out of 5.0 by Worked extremely well for me INSTALLATION TIPS: 1950's era low-slope roof with no attic (interior ceiling is attached directly to 2x6 joists); with rolled roofing (about 10-year old roof). Took 3-hours and 3-1/2 pails to do 1200 sf first coat; 2-hours and 2-pails for second coat. Temps during application were in the 90's with direct sun, medium humidity. Rained hard 8-hours after second coat was complete - no noticeable issues. Easiest way for us to apply was to simply pour a 4-foot splash of paint, then even it out with a roller. First coat went on a bit tan. Second coat went on bright-white (not really blue as is advertised), was easy to tell what needed a second coat. Cleans up with water DID IT WORK? Like a charm. I don't have any actual before temperature readings, but there is an area of open ceiling where the heat just radiated down - roof temps had to be over 130-degrees. Now, in full midday sun, digital thermometer reads 97-degrees (ambient temperature outside was 93-degrees). So it really cut down the conductive heat. WORKS BEST FOR - low-slope roof houses; especially where there is a lot of conductive heat (meaning, where the heat is transferred by surface into the interior space - most houses have an attic with ventilation, so while this would improve the heat transfer, results would be less dramatic). Cost was around $0.50/sf plus my labor to install. I believe it will add a good 5+ years to life of roof, and pay for itself in reduced AC costs (caution - according to CRRC tests, winter-time benefits reverse, meaning you actually need a bit extra heat because the roof reflects much). May 25, 2015
Rated 1.0 out of 5.0 by Junk, will completely wash off in less than a year, will only fix leaks temporarily it is not 100% silicone, this product will not last. September 28, 2015
Rated 5.0 out of 5.0 by Reduced kitchen ceiling temps by over 30 degrees My metal strips supporting my drop ceiling in kitchen add on to house would be too hot to touch in the afternoon even with lots of insulation. The AC Was working hard. After first thin coat applied on Labor day, the strips were only about 78 degrees when it was well over 95 degrees outside. It rained about 5 hours later and nothing leeched off the roof. Put on 2nd coat 6 days later, is so white it hurts to look at it even with dark sunglasses. No doubt that my next electric bill will be lower as it no longer runs as long to cool the house. This is over a mostly flat roof wtih a gentle slope that mostly dries quickly after a rain. Next question, should I try it on the Architectural Shingles? The light gray color is getting darker after 14 years. Would definitely help cool the attic. September 12, 2011
Rated 5.0 out of 5.0 by Wrong specs, 300 sq. ft. coverage per bucket! The coverage area is not 60 sq.ft., it's actually 60-80 sq. ft. per gallon! You should be able to do about 300 sq. ft. with a 5 gal bucket. Read the PDF guidelines on Lanco's website "Apply the first coat by pouring container of Lanco® Ultra Siliconizer™ onto the roof and spreading at a rate of 2-4 gallons per 120-240 sq. ft.." October 24, 2011
Rated 5.0 out of 5.0 by The ONLY One for Asphalt Shingles (and GREAT at it) This was on a 3:12 Sloped Asphalt Tile Roof (18 years old). Someone already said it, but get the MOLD and lose material off of your Asphalt Tile roof. Use a bleach and water mix 10% or 15% bleach and make sure the bleach solution stays on the moldy areas long enough to KILL IT and get rid of it or it may bleed through and possibly affect adhesion. And get all loose material off. Spend several hours with a fairly stiff broom but DON'T BEND or BREAK ANY shingles/tiles (yes, I bent one and snapped it, and glued it back on with a tube of Black Jack I had on hand. Also, I missed cleaning a corner and had to stop since the roller will THROW loose tile facing (sand) in your face, on your clothes and all over everything else. I started with a tray, but DON'T BOTHER. THIS STUFF IS THICKER THAN ANY PAINT I HAVE EVER SEEN! You can't get it on fast enough and it will DRY on the roller before 5 gallons is used - even on cool mornings (I did all work on mornings right after the roof was dried but before it was too hot). I did one 5 gal bucket per morning (took me one week - hey.. I'm 60.. OK? I move slower these days). So I grabbed a 2 quart plastic pitcher and dipped it in the 5 gallon bucket and scraped the sides of the pitcher off with a small squeegee then walked over and poured is out in a line 6" wide across the top and rolled it DOWN the slope of the roof until I got to 8 feet from the bottom and turned around and poured the last lines below (near the edge) and rolled it upward making sure coverage was even and a tad thicker on the edges (I want to keep edge tiles down in the wind). It worked GREAT and I got fairly even coverage - thin enough that I need a second coat on my medium brown colored shingles (I wanted 2, and they recommend 2 anyway), but it was thick enough that the excess seeped down between the tiles for a good seal and even coloring. One of my freshly applied buckets got washed off in a FREAK Rain shower 30 minutes after I applied it. So it took 8 to do 1550 sqft instead of 7 buckets as planned (20% chance of rain my A - -!). 1550 Sq Ft - 7 buckets - 35 gallons. That is 44 sq ft/gal - a bit thicker than the 50 sqft/gal they recommend, but I suspected older shingles would take more, and some would seep and be EATEN between the tiles and I planned for it. I suspect that will even help keep the tiles down in high winds and I checked several and it DOES seep under the edges acting as an adhesive to hold them down, too (that is very good). If it rains within 1.5 to 2 hours, you are going to lose 3 of your 5 gallons into your gutters... get another bucket. I plan to do the next coat across the tiles (perpendicular to first coat) as recommended. Just this first coat literally strengthens the tiles and it does remain a bit flexible and does NOT crack when you walk on it. I am going to add 10 to 15 gallons every year after a soap and water wash down (maybe a small bit of bleach - we shall see). You will need one new 12" ROLLER for every 5 gallon bucket. You may be able to stretch it to two, but it does a number on them. This is some VERY THICK STUFF!! Get this: I can walk on my ASPHALT SHINGLE ROOF AT HIGH NOON, FULL SUN, IN MY BARE FEET! Pretty Cool, eh? (literally... ). And this too: A/C BEFORE Lanco from Noon to 4 PM: 1 HOUR ON, 10 Min OFF (yes, I said ONE HOUR ON). A/C AFTER Lanco from Noon to 4 PM:: 20 min ON, 15 min OFF. I have not seen the first electric bill yet, but that has GOT TO BE SOME BIG BUCKS! Life is good. And I KNOW I added 7 to 10 years to the life of my old roof - maybe more. Pity the roofers when this gets out... Oh..., one bad thing. Since the roof is cooler. The Birds land on it - and DECORATE all over it. But, it does wash off with the rain - unless they have eaten those purple berries. So I get a Polka Dotted roof.... a bit of mild bleach will clean it (I hope). Or maybe I need a scare crow now... FINAL THOUGHTS: HIGHLY RECOMMENDED FOR OLDER ASPHALT SHINGLE ROOFS. VERY HIGHLY!! I have also seen it after about two years on a roof of similar type, and it looks like new (they recommended it to me). Why would ANYONE leave an uncovered asphalt shingle roof with this stuff around? I'll bet it pays for itself in 2 years on just what I DON'T SEND TO FP&L each month! I should have done this 5 YEARS go... (was this stuff around 5 years ago?) September 9, 2015
Rated 5.0 out of 5.0 by Older roof completely looks new! I had a leak on my South Florida home where the back flat roof was 10 years old and starting to leak. I had just at 2000 square ft of flat roof. I used 7 X 5 gal buckets. The roof looks great. Reflects the sun and the interior of the house stays cool. Be sure to prep the roof. I used a stiff broom to sweep all the debris off and cleaned with a mixture of bleach and water. Allowed to dry for 2 days and then applied Ultra Siliconizer. I did 2 coats. 1 then the second 24 hours later. It looks like a new roof. Had many roofers give me quotes for a new roof at 12K. Very happy this stuff works as good as it does. I plan on re coating with 1 coat each year. Should last just about forever. All flat roofs in Florida should be coated with this stuff. But of they did the Roofers would be out a job. January 23, 2012
Rated 5.0 out of 5.0 by Awesome Product I own a roofing company in the Virgin Islands and we do strictly waterproofing and minor repairs of roofs. We have been using this product for many years now and it is the only water based Acrylic product that we use. When properly applied, according to manufacturer's specs, it forms a superb waterproof membrane on your roof that does an awesome job of repelling water. Best when used on roofs with good drainage and little to no water ponding. Be sure roof is properly cleaned first in order to get a good bond. September 13, 2013
  • 2015-11-25 T11:56:17.783-06:00
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