How to Use Fire Cement on Flue Pipe and Other High-Temperature Equipment

Fire cement is a heat-resistant adhesive which can withstand really high temperatures. This is one of the best choices for sealing joints in stoves, fireplaces, and flue systems. In fact, fire cement is commonly used on flue pipes and other high-temperature equipment. This article explains how to use fire cement on a flue pipe.

What do you need to know about fire cement?

Fire cement is a combination of inorganic filters and thermosetting resins. This is actually the best ready-to-use, durable, resistant, reliable, asbestos-free, and long-lasting product with air setting properties that you can use to fix leaks and cracks. It’s available in various dimensions and colours (people often choose black or grey fire cement). It can be used to seal joints in wood stoves as well as central heating systems.

The putty may be particularly useful around the area whereby the flue rises from the furnace. What’s more, the fire cement offers exceptional adhesion to stone, firebricks, blockwork, and clayware. So, if you notice that the cement seal on your flue pipe is broken or crumbled, you can fix it with a fire cement. New fire cement is also necessary when your stove loses some of its colours and becomes an unsightly light grey.

If you’re questioning why fire cement cracks, it is usually because the stove “rocks” a bit when you open and close the stove door and over time, it causes the fire cement seal to crack. The other reason may be the heat cycles that the appliance goes through.

Why is it worth using fire cement?

Using fire cement on flue pipe (and other high-temperature equipment) is reasonable for several important reasons. Fire cement seals joints and gaps, and it prevents the escape of carbon monoxide (and other combustion products) into living spaces. It prevents leaks in the flue system. It’s worth emphasising that having a Carbon Monoxide alarm and testing it regularly is a must. Thanks to fire cement, you don’t have to worry about the reduction of the efficiency of your heating appliance. Also, there is no risk of escape of hot gases.

What’s more, fire cement ensures a long-lasting and durable seal, as it is designed to withstand high temperatures. Fire cement can even be called a protective barrier, which reduces the risk of corrosion of metal components in the flue system. The lifespan of the flue is extended due to fire cement. It’s worth mentioning that safety regulations often require the proper sealing of flue systems for safety reasons. So, using fire cement helps meet those safety standards.

What else do you need to seal joints and gaps except fire cement?

If you want to seal gaps and joints on a flue pipe, you ought to equip yourself not only with a fire cement suitable for your application, but also with a few more materials. So, buy fire cement and then think about other necessary things.

You will need protective gear – safety glasses and gloves have to protect you during the application. Make sure you have a clean cloth or sponge which you will need for cleaning surfaces before application. You may also need a brush or a trowel to spread the cement. When you get your needed materials, you can proceed to the actual process of sealing.

How to use fire cement on a flue pipe? A few easy steps

Start with preparing the surface on which you want to apply the fire cement. The surface has to be clean, with no dirt, grease, dust, and with no pieces of previous fire putty. Clean the surface using a sponge or clean cloth and then let it completely dry. Vacuum around the seal. When it comes to removing the pieces of previous fire putty – use a small screwdriver, but do it carefully in order not to affect the integrity of the stovepipe. Take the fire cement and read the instructions on the package. Following the manufacturer’s instructions is a must, as different fire cements may have different application guidelines.

Mix cement if necessary

The next step involves mixing cement with water before application. However, this is not always necessary, as some fire cements come in a ready-to-use pre-mixed form. So, if you choose the first option, add the required amount of water to a clean container, following the manufacturer’s instructions. Then, add the powdered fire cement to the water. Stir continuously with a clean tool until you achieve a smooth consistency.

Proceed to the application stage

Now you can proceed to the application part. Firstly, make sure that the fireplace cover, collar, and the flue pipe are secured before you apply the new fire cement. Use masking tape around the bottom and top of the seal – it will be easier to apply a clean, straight edge of the fire cement. The excessive fire cement can be really difficult to remove when it’s already dry, that’s why you should try not to let any unnecessary putty dry out on the flue pipe.

Use a brush to evenly apply fire cement to the surface which needs sealing – to a flue pipe. Be sure to cover the flue pipe carefully and properly. The entire area requiring sealing has to be covered. Pay attention to the thickness of the layer. Too thin layer won’t provide a good seal. Too thick layer will be excessive.

Make sure there are no gaps or leaks

When the flue pipe is still wet, you can shape and smooth it for a better-looking finish. Then, let it dry and cure. You can subject the flue pipe to gradual heat. Don’t forget to make sure there are no gaps or leaks left. If there are any, apply additional fire cement. When dried, fire cement becomes a non-flexible solid sealant. The last thing to do is to start a fire in a wood or metal stove (or fireplace). Thanks to that, the fire cement can cure properly. That can also prevent any smoke leaking out.


Using the fire cement on a flue pipe is easy, and it’s not a very long process. Just prepare the area you want to apply the fire cement on, make sure that it’s clean, mix cement if necessary, apply it on the flue pipe, make sure there are no leaks or gaps, and let it dry for 1 hour. After that, you can turn on your appliance.