TAMOSEAL is a cement-based waterproofing treatment that makes a great chimney crown coat. I have been using this product for 15 years plus, and it has made me a lot of money and has handled lots of my customers’ chimney crown leaks. The product comes in a 50lb bag and requires a bonding agent, AKKRO-7T be mixed with it. The bonding agent comes in a 1-gallon container. 

Other uses for Tamoseal

Now this much product will coat a LOT of square footage. Consider that not only is it good for preserving a chimney crown, but it will also waterproof the following:

  • Concrete block
  • Precast concrete
  • Formed concrete
  • Foundations
  • Below grade surfaces subject to water penetration
  • Brick and stone.

Surface preparation/application

A critical point to know when mixing this chimney crown coat is that it has to be mechanically mixed. I use a paint mixer and a cordless drill. The cordless drill allows you to control the mixing speed. If using an electric drill, you will want a variable-speed drill on a low setting to start with. If your drill is too fast it will make a mess of the mixing procedure. You can get a paint mixer for your drill at Home Depot or just about any hardware store or paint store.

Begin surface preperation by using a wire brush to remove any moss, algae, etc. from the crown; don’t skip this step, as you want a clean surface for the product to bond to. After this is complete wet the crown down and let the water soak into the crown before applying Tamoseal. To prepare the Tamoseal follow the directions on the powders package and mix the product up to the consistency of pancake batter. Your mixing solution that you add tamoseal powder to needs to be 3 parts clean, potable water and 1 part AKKRO-7T bonding agent.  I like to use a small, 1/2 gallon bucket to mix tamoseal, which is also ideal if your are working from a ladder. I use an inexpensive 4″ or 6″ wide paint brush to apply the product. It is possible to use the Tamoseal alone without the bonding agent; the bonding agent improves bonding and mechanical properties. Note: when mixing, put the powder in the bucket, then slowly add mixing water. I like to use a margin trowel to do the initial mixing, followed by mechanical mixing with the drill.

Margin trowel

Another critical point is that in order to properly coat a crown with Tamoseal you must apply two coats. You apply the first coat, let it dry, then apply a second coat. This product does a very nice job as you can see in the photos below:

Cracked chimney cap (crown)
Cracked chimney cap (crown)

Tamoseal applied to crown.
Tamoseal applied to crown

If you have some compelling reason to have to do this repair with rain in the forcast, then apply the first coat and then tarp over the chimney to protect it (don’t tarp over the chimney if it has a furnace or other appliance venting out of it- wait for a dry day instead). Do the same for the second coat (if there is still a threat of rain.)

The final coat should be brushed on with the brush marks all going in the same direction as much as possible. This makes for an even texture and finish.

Do not apply the product if the temperature will be below 40 degrees F (4C) or if it will fall below 40 degrees in 24 hours. If there are going to be hot and/or windy conditions, you will have to lightly spray the finished surface several times throughout the day to prevent rapid curing. Wait 12 to 24 hours before applying the second coat. 

Cleaning up after applying the product

It is almost impossible not to smear some of the product onto the first layer of brick that the chimney crown was poured on. The way that I deal with this is to let the product stiffen up somewhat and then use a chisel, putty knife or some similar edged tool to scrape the product off of the brick. follow this with a damp sponge or towel. Thouroughly rinse out paint brushes, sponges, etc. Don’t forget to rinse off your paint mixer drill attachment as well. DO NOT LET THE PRODUCT DRY ON YOUR ROOF. If you get any on the roof, rinse it off as soon as you can. It is difficult to remove it from composition roofing shingles once it has dried.

What do I do with all of this left-over product?

The Tamoseal powder has a shelf life of 18 months in the original, unopened package. The shelf life decreases drastically if you let it get wet! Do not store it in a humid area if at all possible. Having said that, If you have no other uses for the product you may have a friend or neighbor that could use it. You could donate it to Habitat For Humanity or some other local organization. 

The ideal conditions for application

In my  opinion, anywhere between 40 and 80 degrees, on a day when it is’nt going to rain for at least 8 hours and the temperature is not going to drop below 40 degrees. Here is the technical sheet for Tamoseal if you want more exacting data: Click here

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