Tar and most oil based products are not directly compatible with water based products.
In roof coating an emulsifier is used to treat the surface of tar in order to prepare it so a water based product can be applied over it without having issues. If the tar has naturally dried out on its own – which can take years, then my experience indicates water based coating can be applied without using an emulsifier.
I don’t know the following for a fact since I wasn’t there when the work was done, but I’d bet large sums of money emulsifier was not used in the following situations. If it was used then it wasn’t used properly.
This photo shows that extra tar was used along the drip edge. The more tar used, the more oil there is. The additional oils from the thicker tar caused the coating to fail along the edges before failing elsewhere.
Thicker tar again. Notice the spot the the upper right. Its doing better. When oil from the tar is going to cause a failure in the coating it almost always happens sooner in the areas with thicker tar.
More tar along the edges. Failed here first and then started failing elsewhere. This roof needed repair work a few years prior to this photo being taken.
I doubt any emulsifier was used on this roof at all prior to putting on the tan cool coating. My guess is additional patch work was done around the skylights at a later date.
Alligator cracking also called mud cracking. More emulsifier would have helped in the thick area by my business card. This spot was probably still going to dry out and crack anyways, as areas with lots of tar keep drying out for years. As they dry out they shrink and crack. The give away here is the rest of the roof. Its also drying out. No emulsifier or not enough emulsifier.
Alligator crack. This spot was going to crack and not much to be done with it other than to recoat. The area around it is also cracking out and it shouldn’t be.
More alligator cracking.
The entire roof looked like this. The coating was having adhesion issues.
If you notice alligator cracking or dripping tar on your roof feel free to give us a call for a free inspection! If your roof needs to be repaired or recoated we’re happy to give you a free quote!