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Are you thinking about using roofing cement for your next repair project? We’re here to help! Learn more about roofing cement and its uses and decide if it’s a project you’re ready to take on.
When to Use Roofing Cement (or Not)
FIX THIS – Roofing cement can be used on your asphalt shingle roofing to patch small holes and cracks, reattach shingles, reseal around chimneys and flashing, and fix rust spots in metal gutters.
NOT THIS MATERIAL – Roofing cement is not compatible with some materials, including PVC and EPDM (ethylene propylene diene monomer), which can be damaged by the chemicals in roofing cement. EPDM is a synthetic rubber roofing and requires a silicone-based product labeled safe for EPMD. And silicone or urethane is usually recommended for metal roofs.
NOT THIS MUCH – Large holes or widespread damage are not good candidates for DIY patching. Think of times you’ve repaired drywall – a small nail hole is an easy fix with spackle. A larger opening may be repairable with a piece of drywall, plus tape and spackle for seams. But for extensive damage, you’ll call a contractor for replacement.
NOT THIS TIME – The outdoor temperature should be at least 50 degrees Fahrenheit. In colder weather, store roof cement in a 70-80-degree indoor room for 24 hours before application. But working in the cold will be more difficult for you too – just call a pro.
WHEN YOU HAVE AN INSURANCE CLAIM – If your roof was damaged by hail or wind, you might be tempted to avoid the hassle of filing a claim by fixing it yourself. However, that will make it harder to file with insurance later if the damage is more extensive than you thought.
NOT THIS ROOF – If your roof is old and the shingles are brittle, you may do more damage by climbing and working on it.
WHEN IT HAS TO LAST – Cement patches are not a permanent fix. If you don’t want repeat repairs, or you are considering selling the house, call a professional for long-lasting repairs or roof replacement.
What is Roofing Cement, and What Kind Should I Use?
Roofing Cement is a mixture of materials that is based on emulsified asphalt (bitumen), plus mineral spirits, fibers, and additives.
Although it may seem similar to tar, there are differences. Roofing cement forms a waterproof barrier; tar is only water-resistant. Cement is thicker than oily tar and doesn’t run in black streaks down your roof.
Cement is not the same as sealant either. Back to the drywall comparison, cement is comparable to thick spackle, while sealant is thinner and comparable to paint.
Some roofing cement is only for dry weather. If you must repair a wet roof or live in a rainy or humid climate, use cement approved for wet conditions, called dry/wet patch or all-weather patch.
Although the terms asphalt, flashing, and plastic cement are usually used interchangeably, plastic cement may be used to refer to the dry roof or low-slope repair only. When making a purchase, be sure to read all the details on the label to make sure you are purchasing the correct product for your project. *
Read your roofing warranty also, to be sure that you are not using materials or making repairs that might void your warranty.
What is Roofing Cement, and What Kind Should I Use?
Layers of roofing cement should only be 1/8 inch deep. If a hole is deeper than that, allow layers to dry between coats. Around flashing, vents, or chimneys, cement can be applied up to ½ inch deep. Too thick of a layer can interfere with water flow and cause more damage.
- Find the leak if the area of damage is unknown. You may have to go into the attic or onto the roof.
- Gather supplies: sturdy ladder, roofing cement, roofing trowel, roofing paper/mesh, roofing hammer, roofing nails or screws, and safety equipment – hardhat, safety harness, and a mask that blocks vapors if needed.
- Clean the surface. The area must be free of dust and debris, or the patch won’t adhere.
- When patching a blistered area, open the blister and allow the area to dry before starting.
- Make sure any loose roofing nails or screws are replaced or secured in the damaged area.
- For small repairs, place the cement in the hole with the roofing trowel.
- For a wider hole, start with a layer of roofing cement. Add a patch of roofing paper or mesh. Then add a layer of cement on top.
- For loose shingles, put the cement underneath the shingle. If you have to re-nail the shingle or surrounding shingles, put some cement around the head of the nail to seal it.
- Allow the cement to dry and cure.
Note: Do NOT thin out roofing cement. It is not supposed to be thin like sealant or tar.
How Long Does It Take Roofing Cement to Dry?
Drying time varies depending on materials and weather conditions, but the average drying time is 12 hours. For a complete cure, allow 24 hours.
Removing Roofing Cement
Pull away loose cement. Use a wire brush to remove loose debris. Us a chisel or razor edge to pry or scrape away stuck cement. You may need to lift shingles to get roofing cement underneath. On flat metal surfaces such as flashing, you can sand away cement residue.
When removing old cement, remember new materials do not contain asbestos, but some older products did. Consumers who had those products may have used them later than when they were banned from sale. If there is any doubt, contact a professional for removal.
To remove the cement from your hands, use WD-40, followed by soap and water.
