A roof leak can cause chaos in a home. Homeowners need a new roof but can't wait, so they look for a quick solution. This is where roof cement comes in.
Unfortunately, there's a lot of misunderstanding around roof cement. Homeowners can wrongfully use it to patch an asphalt roof back together assuming it can "fix" their roof. But that's not what it's for.
In this article, we dive into roofing cement (not literally, of course... that would be bad). Find out:
- What roof cement is
- Roof cement vs. roof sealant
- When to use roof cement and when to avoid it
- How to use roof cement properly
What is roof cement?
Roof cement comes in several different types, and not all of them do the same thing. Some ads tend to associate the term “cement” with anything sticky that stops a leak.
Roof cement is an emulsion made of asphalt, fibers, mineral spirits, and other additives. Hardware stores sell it to homeowners who want to slow the torrential downpour in their living rooms. Asphalt roof cement is the staple.
Simply put, it’s a material used to temporarily seal leaks, reattach loose shingles, or repair small roof issues. Think of it as a thick, sticky, multi-purpose tool that gives homeowners a short-term solution to an immediate problem.
Roof cement vs. roof sealant
People sometimes confuse roof cement with roof sealant.
Roof sealant is used to create a waterproof seal between shingles or roofing material and roof features like vents, chimneys, etc. It's used in roofing as a tool, not as a quick fix.
Roof cement is a patch item to help fix leaks, reapply shingles, and other roof repairs.
When should you use roof cement?
Reach for it when you need to stop water now and buy time for a real repair: sealing around a pipe boot, patching a small puncture, bonding a lifted shingle, or temporarily sealing flashing before a storm. Also handy for gutters and small seams. Rule of thumb — small, contained, temporary.
When to avoid roof cement
Not every leak can be fixed with a liberal scoop of roof cement. In fact, using too much can cause additional damage to the roof.
Homeowners sometimes use it without fully understanding it. They over apply it near walls, skylights, chimneys, and under shingles, which can restrict the water flow on the roof. As roofers know, this can ultimately lead to more leaks. But homeowners don't know that.
Appropriate uses for roof cement
Yes, roof cement is a patch, but there are cases when it is absolutely appropriate.
Use it to:
- Repair small holes
- Quickly fix for loose shingles
- Seal gaps around chimneys and corners
- Professionally apply a temporary fix before permanent repairs
Roof cement is useful for temporary repairs, but it should not replace getting a new roof.
Types of roof cement (and when to use each)
Wet vs. dry roof cement: which one and when
Standard roof cement needs a clean, dry surface to bond. If it's raining or the roof won't dry before the next storm, that's what wet-patch (wet/dry) cement is for. It's formulated to grab damp and even wet surfaces. Use wet-patch for emergencies, standard cement for planned repairs on a dry day.
How to apply roof cement
First thing's first when getting on a roof: think about safety. Whether you're patching a homeowner's roof for bad weather or doing a full replacement, put on your harness and other safety equipment.
If you're new to roofing, be sure to read the instructions on the roofing cement. You'll also want to make sure that you have all of the tools that you’ll need before you get started.
With safety gear and tools, you're ready to go!
Assess and clear the area
Make sure that the area is free of debris and that you’ve removed any materials that could complicate the application. This is as much for proper adhesion as it is for safety.
We know you want to help homeowners no matter what, but if the roof isn't safe to get on, don't do it. We know water is scary in a house, but in extreme weather, you should not be climbing onto a roof.
Find damaged shingles
Look for damaged shingles, and any obvious signs that areas of the roof are damaged. It can be a good idea to get homeowners to point our any leaks before you climb up so you know where to look. Once you’ve identified the problem, you can start gluing shingles back into place.
Use your trowel and putty knife for cracks or holes
Identify the borders of the hole or crack that’s letting water in first. Gently use your trowel or putty knife to pack the roof cement into the area. Don't push too hard or be too aggressive, or you can cause further damage.
Consider patches to help with larger areas
For large areas of damage, use rolled roofing, fiberglass, or polyester as an extra patch. Coat the back of the material with roof cement, and then apply another coat over the top for maximum protection. Again — this is a quick fix! Don't do this when completing a new roof replacement.
Replace the shingles
After the area has been repaired, it’s time to replace the shingles. If you can't replace them right away, tarping the area is a good temporary option.
If you do have to reattach shingles, start at the bottom. Use roofing nails to attach each shingle from bottom to top. Then, use a small amount of roof cement to secure the final shingle.
Insider tips and warnings for using roof cement
Roof cement is available for homeowners, but they shouldn't mistake themselves as a roofer. If you are using roof cement to patch, consider calling a professional instead.
Before climbing that ladder and tackling your roof repairs, there are some things to remember:
- When working in colder weather, leave your roof cement inside overnight.
- Avoid using roof cement while smoking or around open flames.
- Check the weather before planning your roofing project.
- Make sure that the roof cement you purchased is the right formula for your needs.
Educating homeowners on quick fixes
If you're doing a patch job with roofing cement on a house, make sure to walk homeowners through the points explored here. Talk about how:
- Roof cement is a patch job.
- There are limitations and dangers of over-using this fix.
- It's still important to do a permanent fix for roof leaks.
If you do offer patch jobs and roof repairs, make sure you have a process in place to track those customers and nurture them. Email, text messages, follow-up phone calls, and other marketing efforts can help convert those one-time customers into a full-on roof replacement.
Roof Cement FAQs
What is roof cement?
A thick, asphalt-based sealant used to patch leaks, seal flashing, and bond roofing materials. It's a short-term repair — good for stopping a leak fast, not for replacing proper flashing or a failing roof.
Can you use roof cement on shingles?
Yes, for spot repairs like sealing a lifted tab, bonding a loose shingle, or patching a small hole. Use a small amount under the shingle and press it flat. It's a fix, not a substitute for replacing damaged shingles.
What's the difference between wet and dry roof cement?
Wet/wet-patch cement is made for damp or wet surfaces during a leak emergency. Standard (dry) cement needs a clean, dry surface to bond. Use wet-patch when you can't wait for the roof to dry; standard for planned repairs.
When should you avoid roof cement?
Avoid it as a permanent fix for flashing, valleys, or widespread damage. Over-applied cement traps moisture, cracks over time, and makes a proper repair harder later.
How long does roof cement last?
A good patch typically holds for a few years, not decades. Treat it as a stopgap and plan the real repair — temperature swings and UV break it down.