 Can-Do Guide®: Installing & Repairing Cold Applied Built-up Roofs
What is Cold Applied Built-up Roofing?
A cold applied built-up roof is a roof membrane assembly made up of several layers of roll roofing, bonded together with Cold-Ap® Cement. Cold applied built-up roofs offer excellent durability, are easy to maintain, and relatively lightweight. The cold application process also eliminates the hazards of using hot asphalt. Safer, simpler and more efficient, cold applied applications do not require specialized equipment, and produce a stronger, more reliable roof.
Uses for built-up roofing:
 | new construction
| | reroofing over existing built-up roofing
| | homes with parapet walls around the roof perimeter
| | industrial and commercial buildings |
Installing a Cold Applied Built-up Roof
- Cut and flatten any blisters, buckles, and raised edges. Check flashings, edging, drains, valleys and vents, and repair as needed. (See Henry® guide, “Repairing roof leaks.”) Roof surface must be dry, clean, and free from oil, grease, rust, scale, loose paint, dirt, and gravel.
Older roofs may need to be removed entirely if: - The roof deck is deteriorated and does not provide a sound subsurface. The structure has been reroofed several times, causing excessive weight load. There’s moisture in the old roof which won’t dry without removal. Local building codes require it.
IMPORTANT: The weather should be at least 65°F, dry and clear with no threat of rain for 48 hours.
Henry 203 Cold-Ap Cement is applied uniformly with a roofing brush or roller, between layers of roll roofing at the rate of 1.5 gallons per 100 square feet. Stir Henry 203 cement to uniform consistency before using. Do not thin. Roll roofing may be placed up to 1 hour after cement is applied. Drying time is about 48 hours in warm, dry weather. If a corner or edge of the roofing can be lifted, the cement needs more time to dry. - Nail the first layer of roll roofing to the roof deck, using large head galvanized roofing nails. Nails should be long enough to penetrate 3/4" into the roof deck. Where the deck is less than 3/4" thick, the nail should be long enough to penetrate fully and extend at least 1/8" through the roof deck. Use three rows of nails per strip of base sheet: (a) 1" from lower edge of sheet, spaced 9" apart, (b) 12" from lower edge, spaced 18", and (c) 24" from lower edge, spaced 18". Do not use 203 Cold-Ap Cement for the first layer unless the deck is concrete or another non-nailable surface.
- For the second and third layers, apply Henry 203 evenly and uniformly between each of these next two layers of roofing. Be sure to get full coverage.
- While the cement is tacky, press the roll roofing into the cement by brooming, then roll with a weighted roller several hours later. Adhesion is improved by brushing the underside of the sheets at the laps with a thin film of cement. Also brush cement on the underside of sheets where they go over metal edges, vents and wall flashings. Avoid over-application, and remove excess cement from exposed surfaces. Henry 203 adheres permanently when the solvent evaporates.
- After 203 Cold-Ap Cement has thoroughly set, apply Henry 107 Asphalt Emulsion Roof Coating over the new surface. (See Henry guide, “Protecting your roof with asphalt coatings.”)
- Let emulsion cure for 7 to 10 days, then complete the job with a Henry reflective coating. (See Henry guide, “Protecting your roof with reflective coatings.”)
IMPORTANT: Contact the roll roofing membrane manufacturer for their recommended product application instructions.
Repairing Loose Seams or “Fishmouths” - Re-seal loose seams by brushing Henry 108 Lap Cement between the plies of overlapping sheets and apply pressure to form a new bond.
- Nails that have broken through from the selvage edge beneath should be replaced with larger nails and top coated with 208® Wet Patch® Roof Cement or 209 Elastomastic®.
Recommended tools:
 
|
