I just spent the last week learning about the plastic roofing cements that Bakor Company makes, and I thought I'd share the knowledge. I'll use Bakor's prices (approximately) and part numbers, but every company has a similar line of products:
- Plastic Roof Cement (product # 810-20) This is the least technological roofing cement offered by Bakor. It's basically asphalt with fiber and fillers mixed in with it. It'll give you good durability, although it is messy to work with because of it's asphalt base. This product needs to be applied to a DRY surface. This stuff costs about .50 for a 300 ml caulking tube.
- Durable Roof Patch (product # 810-21) This is Circa 1990 plastic roofing cement technology. This plastic roofing cement can be applied to a wet surface, so it'll work if you have to patch your roof while it's raining. This stuff costs about .00 for a caulking tube, and the difference in price is really for the chemical wizardry needed to get a asphalt based product to stick to a wet surface. Other than it's ability to stick to a wet surface, this roof patch gives no better performance than the older technology in the 810-20 product.
- Polybitume Sealing Compound (product # 570-05) - This is actually a different chemistry. It's still based on asphalt technology, but the plastic that's formed will not only stick to a wet surface, it'll be more water resistant than either of the previous two products once it's cured. So, in this case, the extra money you're paying is buying you greater weathering and water resistance. Because this product is more water resistant, it's also recommended for low slope roofs where water tends to collect in puddles until it evaporates rather than drain away. It's that higher water resistance needed for a low slope roof where you really need this stuff instead of the previous two that are just based on asphalt technology.
- Ultimate Roof Patch (product # 810-47) - I'm not going to pretend I know the chemistry of this stuff. It's got no connection to asphalt anymore because the stuff is yellow or white in colour. It's the most resistant to weathering and water, so the extra you pay for this stuff translates directly into greater durability.
Now, say you wanted to have the toughest roof repair in town... What you would do is:
- clean the surface to be repaired of all loose dirt.
- apply one coat of Ultimate Roof Patch
- apply a layer of Bakor "Yellow Jacket" (product # 990-06) which is similar to fiberglas mesh drywall tape on steroids. It comes in a 6 inch wide by 50 foot long roll for residential customers, and a wider and longer roll for roofing companies. The purpose of the fiberglas mesh is to prevent forces of tension from causing the repair to crack. For the repair to crack, the fiberglas mesh has to stretch, and fiberglas is very strong in tension. Overlap the Yellow Jacket at the corners.
- Apply another coat of Ultimate Roof Patch over the Yellow Jacket
- Apply clean pea gravel to the top coat of Ultimate Roof Patch to keep the UV light from the Sun off so that the repair lasts forever.
And, my experience with flat roofs is that the procedure for repairing a leak in a flat roof with Ultimate Roof Patch is EXACTLY what roofing companies used to do 25 years ago using ordinary asphalt based roofing cement (810-20) instead. Back then the fiberglass mesh tape was green in colour and wider, but I expect I was just using a different company's "mesh" back then. (Amongst roofers, the fiberglas tape used in roof repairs is simply called "mesh".) I don't know if there are any other differences between the fiberglas mesh tape used back then and the "Yellow Jacket" Bakor markets nowadays.
And, of course, if a person wanted to make a "Megatron" roof patch, they could use multiple layers of Ultimate Roof Patch and "mesh" and maybe use steel flashing over the repair instead of pea gravel to keep the light off of it. (Metals are the most opaque substances known to man. You can stop more UV light, and every other type of electromagnetic radiation, with aluminum foil than you can with any other material of equal thickness. But a bed of pea gravel works very well.)