3. Prep Work
Especially when foam is being applied over an existing roof, the prep work is extremely important. Roofing contractors have been known to show up, spray foam on the roof, coat it, and leave it. Such an installation may provide relief from leaks for a short period of time, but the building owner will experience problems over time.
In order to do a good job, the roofer must prepare the surface, repair damaged sheathing, replace sheet metal and flashings when necessary, deal with drainage problems, and apply protective coatings and foam correctly.
4. Surface Prep
To establish a solid bond, all loose material must be removed from the existing roof. The loose gravel must be removed by sweeping and hauling it away. There may be built-up areas with asphalt and gravel. If that material is coming loose, we use a tool to scrape it off.
We clean the membrane by sweeping up any accumulated silt, then blow the residual dust off with a gas-powered blower. We power-wash the roof if it doesn’t leak.
Even though sprayed foam is highly adhering, it is still a good idea to prime the existing surface. We spray a special primer on the surface of the roof using an airless sprayer.
5. Sheathing Repairs
We will replace or strip the framing and sheathing if necessary if we find rot on a roof.
If the building code does not require a Class A fire rating, we prime the sheathing and then apply foam.
We normally nail a fiber-impregnated gypsum board over the patched area before priming and applying foam to achieve a Class A rating.
6. Metal Work
We may reuse the existing sheet-metal vents, but we always install new foam stops along the roof edge.
7. Edge Metal
The edge of a roof is normally one of the weakest points. For reinforcement on the roof edges, we use a metal foam stop that’s hemmed and kicked out at the lower edge.
8. Vents and Fans
If we strip the roof, we may need to replace the existing roof jacks. If we are simply doing a sweep and the jacks are still in good shape, we leave them in place and cover them with foam.
All unsatisfactory vents are replaced.
Existing roof-mounted vent fans can present a challenge because the foam could elevate the surface of the roof sufficiently for water to run into them. We install a custom-made vented cap over the top of each fan and build a curb around it. The old fan will remain in place and may be serviced or replaced in the future.
Don’t allow a roofer install foam in the roof fan without considering the likelihood of a leak or the potential for a need to replace the fan someday.
9. Drains and scuppers
Most of the structures we work on have scuppers or metal dropout drains that connect through the overhang to a downspout below. When we replace the edge metal, we also replace the scupper linings. Also, we cut out and replace the dropout drains. It is possible that they are rusting through, so we need a new, clean surface for the foam to adhere to.
10. Counterflashing
Under certain circumstances, foam can self-flash when lapped up against adjoining vertical walls. Most of the time, though, a counterflash is needed at the roof-to-wall junction to ensure water located behind the wall cladding is redirected onto the roof.
11. Skylights
Skylights are a known source of leaks. Frequently, we raise the curbs so the skylight is protected above the foam. Never allow a roofer to foam on the skylight flange. The skylight should be easily removable from the roof so that it sits above any water or rain splash. During the reroofing process, we remove the skylights, build up the curb (if necessary), foam up to tops, and then install the skylights over foam weatherstripping. The roof foam does not require curb flashing or cant strips since it is self-adhesive and self-canting.
12. Equipment Curbs
Heating and air conditioning systems are often installed on flat or low-slope roofs. Using sleepers applied directly to the roof is asking for trouble and should be avoided at all costs.
Equipment should be put on boxed curbs with sheet metal caps. The equipment is separate from the roofing system so it can be replaced without damaging the roof, and the roof can then be maintained without moving or removing the equipment.
13. Spraying Foam
When the preparation work is completed and the weather is right, the foam can be sprayed. The deck must remain dry, and the air should be warm. There should not be much wind. Moisture could disrupt the chemical reaction that forms the foam, resulting in a degraded product.
Wind can increase the amount of overspray and affect the texture of the foam. The surface must be warm (above 50 °F).
Our technicians are willing to stop operations when the conditions are not favorable.
We mask skylights, shingles, sidewalls, etc., to prevent overspraying. When we mask the edge metal, we can apply foam up and onto the edge. We spray the details first, like the edges and the roof jacks, and then we spray the field. We can walk on the foam in a few minutes since it cures quickly.
14. Grinding and detailing
The foam is then brought flush to the edge metal with a grinder, so it slopes smoothly into drains and scuppers. We grind down the foam where it looks too high or is awkward. Detailing involves the use of polyurethane caulking at critical points where the foam meets another material.
15. Coating and Granules
An elastomeric coating is then applied to the foam to protect it from UV degradation. If the foam didn’t have this coating, it would eventually wear out.
To achieve the specified 24-mil to 28-mil coating, two coats are necessary and it takes about 3.0 to 4.0 gallons per square. Due to grinding, we precoat any areas that have been ground.
16. Base Coat
This type of coating is applied like a heavy paint; we brush in the details with a brush or roller, and spray the field with an airless sprayer. The base coat is tinted, so we can tell if we miss some spots with the top coat. The tint also shows through when the top coat wears out, so it functions as a recoat indicator.
17. Top Coat and Granules
After the base coat has cured (usually overnight), we spray on a top coat; before the top coat dries we embed a layer of mineral granules.
Besides creating a more uniform appearance, granules offer several functional advantages.
they speed up evaporation of rooftop water
they resist abrasive wear
they stop birds from pecking at the foam
A superior-quality granule provides additional resistance to UV rays. A typical SPF roof lasts about 12 to 15 years without recoating.
A recoating process involves power-washing the roof, applying primer, and applying a top coat. The cost of re-coating a 2,500 square foot roof will be $3 to $5 per square foot per inch.
Call Norris Spray Foam if you are looking for Industrial Roof Replacement in or near Desoto and want to explore spray foam for your roofing project.
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DeSoto is a city in Dallas County, Texas, in the United States. As of the 2010 census it had a population of 49,047. DeSoto is a suburb of Dallas and is part of the Best Southwest area, which includes DeSoto, Cedar Hill, Duncanville, and Lancaster.
Things to do in DeSoto.
