Tackling a gravel roof

From UV protection to fire resistance, gravel roofs have a lot of benefits. But the challenge comes when it’s time to restore them.  

When home and building owners think of a roof, they probably think of shingles, tile or some sort of fluid-applied system (even if they don’t know the name for that). What they probably don’t think of is gravel. But gravel can actually be used in a variety of roof systems. Oftentimes you can find it as the final surface layer in built-up roofing (BUR) systems. To learn more about the use of gravel in roofing systems and how one might tackle restoring a roof that features gravel, Karen Edwards sat down with Greg Hlavaty of Western Colloid for an episode of the Understanding Roof Restoration podcast. 

Greg opened the conversation by discussing the role of gravel on a roof in depth. He shared, “Gravel does three things. It adds a little bit of weight to the roof for things like wind resistance. Then it adds UV resistance, because no sun's going to get through that. It doesn't keep the temperature cool if it's a hot day, but it doesn't let the UV in. If you keep a good heavy layer of gravel on there, no UV is going to get through and degrade that asphalt. Next it is fire resistance. If you put enough gravel on a roof you can get a fire rating with paper towels. It is a barrier to the heat.” 

Where gravel becomes a challenge for many contractors is when it comes time to replace it and restore the roof it is a part of. But it’s not an impossible challenge. Greg explained how you would start a gravel restoration job, sharing, “The first thing they'll do though on a gravel roof, is they'll sweep it and vacuum it. We always recommend a vac, sweep, vac. Where they vacuum it, sweep it with either a power broom or a very stiff bruise, then come back and back it again. There's a layer of gravel that is uniformly embedded into that asphalt. That doesn't come off very easy.” 

Once that’s done, it’s time to put something new down. What Greg and Western Colloid have recommended for decades is asphalt emulsion. “An asphalt emulsion is an asphalt that isn't readily flammable. It is relatively inexpensive, so you can use in the higher quantities,” Greg explained. “Asphalt emulsion is a combination of a straight run distilled asphalt, one that's not been oxidized like hot mopping asphalt… It is mechanically ground with a bentonite clay. It becomes a colloid product and once the water evaporates, it's a combination of bentonite clay and asphalt.” Restoring a gravel roof with asphalt emulsion not only waterproofs it, but it does so at a low cost that makes it accessible to many clients.  

Check out the entire podcast to learn more about restoring gravel roofs.