Want to save some money and do it yourself ? No problem. First thing you need to do is get that roof clean. In the process of cleaning the roof you will discover any areas which will need extra attention. Keep an eye out for any cracking, peeling, or openings in the roof surface. Also look out for any puddling or ponding problems .Building up of ponding areas may be needed. I use a pressure washer, but you can do it with a hose and a good stiff broom and lots of elbow grease as well. Pressure washers can be rented from your local rental center. Always use TSP or a plant safe cleaner when going over aluminum roof coatings to remove as much of the oils as possible. I do offer pressure washing service as well. For a minimal fee I will pressure wash your roof for you.
Next you will want to perform any needed repairs, and general sealing of all high stress areas. .( all vent stacks, skylights, chmneys, projections, corners, etc...)
Any openings in the roof surface larger than an eighth of an inch should be three coarse sealed. Three coarsing is the process of applying patching material a reinforcement and another layer of patching materials. I only use elastomerics with elastomeric roof coating, but some use plastic roof cement( PRC ). PRC is made of petroleum products and needs to be allowed to cure prior to coating with elastomerics. PRC is much less expensive, and when exposed breaks down quickly. Some patching materials have a reinforcement added. I prefer to use an elastomeric patch compound with a polyester reinforcement.
Next you will apply the roof coating. Most will be rolling it on with a roller, but there are some sprayers that can spray roof coating to be rented. I usually apply a 12-40 inch wide polyester reinforcement in minor ponding areas and valleys which lead to scuppers/canellis (drains) that puddle/pond. ( extreme ponding may need building up of roof surface with other materials).
I believe the best way to apply any coating to a rough surface is to roll the material into the surface back and forth with multiple passes of the roller. This forces the material into all the needed areas. However the best way to get a uniform surface thickness and a smooth finish is to spray the coating. I have a sprayer which can spray elastomerics so I spray back roll, and then go over one more time with the sprayer to smooth out the finish and make the coating wear evenly. Rolling creates hills and valleys in the coating this is why some roofs show the underlayment coming through in the low spots of the roller knap. Spraying creates a uniform thickness. So the best in my opinion is a combination of both methods.
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