Short answer, yes, usually. Longer answer, it depends on how you install it, where you install it, and how long you expect it to behave itself before problems start showing up. Roll roofing is simple looking, almost too simple, which makes people assume it sticks on its own and that’s that. Reality has more wrinkles.

Roll roofing is asphalt based. Asphalt likes heat, pressure, and time. It does not love open seams, cold mornings, or water sitting around with nothing stopping it.

What roll roofing is actually designed to do

Roll roofing is meant for low slope roofs, sheds, garages, porches, and temporary structures. It is not built to perform like architectural shingles. The material is thinner, lighter, and comes in long rolls instead of individual pieces. Because of that design, it relies more heavily on proper fastening and sealing to stay waterproof.

Sealcoating is essentially the application of a protective layer over asphalt surfaces. This layer acts as a barrier against elements such as water, oils, and UV damage, all of which can significantly deteriorate asphalt over time. The sealant used in this process is a blend of asphalt cement, water, mineral fillers, and other additives to enhance durability and appearance.

https://www.greatsealcoating.com/how-cold-weather-affects-sealcoating

Most roll roofing products are rated for slopes as low as 1 12, but that rating assumes correct installation. Miss a seal or rush a lap joint, and water finds its way in faster than people expect.

How roll roofing holds water back in the first place

Water resistance in roll roofing comes from overlapping seams, asphalt saturation, and adhesion at the laps. Nails alone are not enough. Nails hold the sheet in place, but they do not seal the edges. Water moves sideways and upward through capillary action, especially on low slope roofs.

This is where sealant enters the picture. Without it, seams depend entirely on gravity behaving politely. Gravity does not always cooperate.

When sealant is absolutely required

There are situations where skipping sealant is asking for trouble. Low slope roofs below 2 12 pitch almost always need lap cement or roofing sealant at seams. Wind driven rain can push water under overlaps that look fine from a distance.

Cold climates also increase the need for sealant. Asphalt stiffens in lower temperatures and does not self seal as well. Sealant compensates for that lack of natural bonding.

Roof edges, penetrations, vents, and transitions always need sealant. Anywhere the material stops being flat and continuous is a weak point. Leaving those areas unsealed is one of the most common reasons roll roofing fails early.

When manufacturers say sealant is optional

Some roll roofing products are marketed as self adhering or mineral surfaced with adhesive strips. These can sometimes be installed without additional sealant if conditions are ideal. Ideal means warm temperatures, correct overlap spacing, clean substrate, and proper pressure during installation.

Even then, many professional installers still add sealant at seams. It is cheap insurance. A tube of roofing cement costs far less than tearing off a leaking roof later.

Types of sealant commonly used with roll roofing

Asphalt based roofing cement is the most common choice. It bonds well with the material and stays flexible as temperatures change. Some installers use modified bitumen sealants for added elasticity.

Silicone and acrylic sealants are generally not recommended for primary seams. They may stick initially but often fail to bond long term with asphalt surfaces. Compatibility matters more than brand loyalty here.

How much sealant is typically used

A standard roll roofing installation may use one to two gallons of roofing cement for seams and details on a small structure. Larger roofs use more, especially if multiple seams and edges are involved.

Industry installation guidelines often recommend a continuous bead along laps, not dots or occasional smears. Skimping on coverage defeats the purpose.

What happens if you skip sealant entirely

Some roofs survive without sealant, for a while. Those are usually steeper slopes with perfect overlaps and limited exposure. But failure tends to be sudden. Once water gets under a seam, it spreads fast.

Leaks from roll roofing often show up as dark stains, soft decking, or blistering material. By the time it is visible inside, damage has usually been happening for months.

Lifespan impact with and without sealant

Roll roofing typically lasts 5 to 10 years under normal conditions. Installations that include proper sealing often reach the upper end of that range. Unsealed installations tend to fail earlier, sometimes within 2 to 4 years depending on exposure.

That difference is not theoretical. Contractors who replace roll roofs often see the same pattern repeated. Open seams, dried edges, no cement used.

Final thoughts

Roll roofing does not forgive shortcuts. Sealant is not an accessory, it is part of the system. While a few products claim otherwise, real world performance shows that sealing seams improves durability, reduces leaks, and extends service life.

If the goal is short term coverage, skipping sealant might feel tempting. If the goal is fewer headaches and fewer repairs, sealant earns its place every time.