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Modified bitumen, smooth built-up, granulated cap sheet

Coat modified bitumen and built-up roofs in the right order

A mod bit, smooth built-up or cap sheet roof that is attached, largely intact and dry can be restored in place. Here is the Sherwin-Williams Uniflex system by part number: repairs, details, then the MB base coat under an acrylic finish, or Silicone44 with no base coat where water stands. Before you budget, our drone moisture scan gives you the map, video from the flight and a written assessment.

Request a quote Request a moisture scan
A contractor seen from behind spraying white coating across a dark modified bitumen roof

Is this roof a candidate

A weathered roof qualifies; a loose or soaked one does not

Asphaltic roofs age in familiar ways: granules shed, smooth surfaces dry out and alligator, blisters rise, laps split and flashings tear at curbs and parapets. Found in places, each is a repair line ahead of the coating. What rules a roof out is wider: a field come loose from what it sits on, splits running through the field rather than at the laps, a cap sheet worn down to the mat, or wet insulation over a large share of the roof. Applied over a sound, dry roof, a restoration system adds 10 to 15 years of service life.

  • Attached: the field still fixed to what it sits on, not lifting or loose
  • Largely intact: blisters, splits and open laps that can be repaired one by one
  • Dry insulation: where no gravel or ballast covers the roof, a thermal scan maps what looks wet
  • Wet areas cored to confirm, then cut out and replaced before anything is coated
  • A sound deck: anything structural is the building engineer's call
  • Drainage that works, or low spots that can be built up at drains, in valleys and along parapets

How the scan works

The build-up

What goes on, from the existing roof up

Read it from the bottom. The existing roof stays, less any wet areas cut out and replaced. Repairs and low spots come first, then an asphalt emulsion resurfacing, only where the surface is extremely dried out or heavily alligatored. The details are three-coursed in fabric, and the MB base coat goes across the whole field as the first coat, with no primer under it. The aluminum route swaps the base and finish coats for an aluminum coating; its data sheets list smooth built-up, mod bit and granulated cap sheet. Silicone44 takes neither the MB base coat nor the asphalt primer.

White system, on a roof that drains

  • Finish coat KST041300 Or commercial grade KST041500
  • MB base coat KST041510 The first coat across the field; no primer
  • Fabric KST20385B Three-coursed at seams, laps and flashings
  • Emulsion KST040312 Only where extremely dried out
  • Slope Builder KST0SLPBD Low spots built up
  • Roof cement KST058600 Repairs and core patches
  • Existing mod bit, BUR or cap sheet Attached and largely intact
  • Insulation and deck Dry: wet areas replaced first

Aluminum route: aluminum KST020475 in place of the base and finish coats, no base coat and no primer named

Silicone44 where water stands: Bleed Blocker Primer on newer asphalt (we do not stock it), then the silicone, with no MB base coat

Order of application, read from the existing roof up. Illustrative diagram — proportions are not to scale.

Order of work

From the repairs to the finish coat

The white system on a roof that drains, in the order it goes on. The data sheet names the preparation, the rate and the cure for each product, a written specification wins over this list, and an adhesion test patch settles whether it holds on this roof.

  1. Clean, cut out what is wet, repair

    Wash the field and clear ponded silt and loose granules. Wet areas the cores confirm are cut out and replaced to matching thickness. Blisters, splits and open laps are repaired, and core cuts patched, with wet-dry roof cement KST058600, which takes a repair on an asphaltic roof wet or dry.

  2. Build up the low spots

    Slope Builder KST0SLPBD, a powder mixed with water on site, fills low areas at drains, in valleys and along parapets, and forms crickets behind rooftop equipment, before anything is coated. Where the water stands because the deck deflects, that is a question for the building's engineer.

  3. Resurface a dried-out roof, only if it needs it

    Where smooth built-up or mod bit is extremely dried out or heavily alligatored, fibered asphalt emulsion KST040312 resurfaces it, with fabric, so the coating has something whole to go on. It is a resurfacer, not a finish, and it cures before the next coat. A roof that is only weathered skips this.

  4. Three-course the seams, laps and flashings

    Every lap, seam, curb, pitch pan and flashing gets coating, polyester fabric KST20385B and coating again, before the field is coated. KST20385A, the narrower roll, suits the smaller details.

  5. MB base coat: the first coat, no primer

    Elastomeric MB base coat KST041510 white, or KST041512 gray, goes across the whole prepared field; a gray base under a white finish lets the crew see coverage. It is a base coat only and takes an elastomeric finish. Skipping it is how asphalt stains through a white finish.

  6. Finish coat

    Premium acrylic KST041300, or commercial-grade KST041500, over the base coat. On a granulated cap sheet the granules take more coating per square than a smooth surface, so count it as its own line on the order. Where water stands, the finish changes, as set out below.

Estimate the material

By part number

The materials, in order

Cement, Slope Builder, emulsion, fabric, MB base coat and acrylic finish, then silicone for where water stands and fibered aluminum for the budget route. Genuine and sealed, in stock, shipped in 1–3 business days.

Where water stands, and the budget route

Two things change the finish: water and budget

Acrylic is the finish for a roof that drains; under prolonged ponding it can lose adhesion and peel. Under Silicone44 there is no MB base coat: repair and wash the roof, put Uniflex's Bleed Blocker Primer down where the asphalt is newer or likely to bleed through (we do not stock it, so ask on the quote form), seal seams and flashings with the black MS hybrid sealant KST058310, then coat. Silicone44 does not fix drainage: Uniflex's silicone specifications still expect 1/4 in per ft of slope and working drains. Whether the deck can carry standing water is the building engineer's call.

  • Where water stands: Silicone44 KST044300 (white) or KST044320 (gray), with no MB base coat and no asphalt primer under it; or solvent-based KST042200 under KST042100
  • A granulated cap sheet takes more coating than a smooth surface, whichever finish goes on
  • Budget route: aluminum KST020475, KST020480 or non-fibered KST020418, listed on smooth built-up, mod bit and granulated cap sheet alike, with no primer named
  • Aluminum goes on a pressure-washed, fully dry roof at 50 °F or warmer, with no rain forecast
  • Black asphalt primer KST020412: only to rejuvenate dried-out smooth built-up and mod bit; not for granulated surfaces
  • The solvent-based pair, the asphalt primer and the aluminum coatings ship as regulated freight

Aluminum and asphalt coatings, compared

Questions

Coating mod bit and built-up, asked plainly

Do I need a primer on modified bitumen?
Not under the acrylic system. The MB base coat KST041510, or gray KST041512, is the first coat on mod bit, smooth built-up and granulated cap sheet, and Sherwin-Williams lists the same product as its Elastomeric MB Primer. Under Silicone44 there is no MB base coat; where the asphalt is newer or likely to bleed through, Uniflex's Bleed Blocker Primer goes first, and we do not stock it, so ask on the quote form. The black asphalt primer KST020412 only rejuvenates dried-out smooth built-up and mod bit ahead of aluminum; it is not a required first step.
Will asphalt stain through a white coating?
It can. That is why the acrylic system on these roofs starts with the MB base coat KST041510, listed for smooth built-up, mod bit and granulated cap sheet, and is then topcoated with an elastomeric finish such as KST041300. A white finish laid straight onto the asphalt is how the staining starts. Under Silicone44, Uniflex's Bleed Blocker Primer goes onto newer asphalt first; we do not stock it, so ask on the quote form.
Can a gravel-surfaced built-up roof be coated?
Not with the build-ups on this page: the base and finish coats list smooth built-up and granulated cap sheet, not gravel-surfaced built-up. Send that roof through the quote form and we will check it against the current Uniflex documents before anything is priced. A gravel surface is a poor fit for a thermal scan too, so that roof is usually surveyed another way: a capacitance or nuclear survey on a grid, then cores.
Can aluminum go on a granulated cap sheet?
Yes. The current data sheets for the 500 Premium (KST020475), 300 Commercial (KST020480) and Superbrite non-fibered (KST020418) aluminum coatings list metal, smooth built-up, granulated asphalt and granulated or smooth modified bitumen. No primer is named for any of them: pressure-wash the roof, let it dry completely, and coat at 50 °F or warmer with no rain forecast. The black asphalt primer KST020412 is a rejuvenator for dried-out smooth built-up and mod bit, not for granulated surfaces.
How much more material does a granulated cap sheet take?
More than a smooth surface, because the granules take more coating per square. We do not print a rate: the data sheet names it for each coat. Count the cap sheet as its own line and each roof level separately; the material estimator turns area and rate into gallons, pails and drums.
Should the roof be scanned before it is coated?
Where there is insulation under the membrane and no heavy gravel on top, yes: coating makers, Sherwin-Williams included, require wet insulation to be found and replaced before a coating goes on. On an evening after a sunny day a drone with a thermal camera flies the roof. You get a map with any areas that look wet outlined and measured in square feet, video from the flight and a written assessment, and cores confirm the flagged areas. On a surface already coated white the scan is the wrong tool, and a white coating makes later thermal work harder.
Can a restored mod bit roof carry a manufacturer's warranty?
Sherwin-Williams offers UNIGUARD system warranties of 10 or 15 years when one of its authorized contractors applies the system. The warranty is the manufacturer's, issued under its own terms; we supply the materials. The manufacturer inspects the finished roof before it issues one, so if a warranty is wanted, say so at quote time and the material list follows that specification. The goods carry our seller's warranty: as described, and free of manufacturing defects when delivered.
Who applies the system?
A roofing contractor; we never do the roofing work ourselves. If you already have one, we supply the materials to them. If you do not, we work with a network of installers, roofing contractors who apply these systems, and can introduce you to one anywhere in the US, who looks at the roof and says whether it is a good candidate for restoration. Roofing and coating contractors who apply these systems can ask to join the network through the quote form; a person answers.

The adhesion test patch

Price the system for this roof

Send the area of each roof level, the surface (mod bit, smooth built-up or cap sheet), the detail lengths and whether water stands. Building owners can start with the moisture scan; nothing has to be decided until the map is in.

We reply within one business day.

Request a quote Request a moisture scan