Cleaning the fireplace chimney

Q: I use my efficient wood-burning fireplace a lot. The chimney has never been cleaned and the exterior is weathered. Is it really important to have it cleaned and what tasks can I do myself?

A: There is some maintenance that you can do yourself, but you must first have a chimney sweep professionally clean the chimney. Cleaning also includes a full inspection. Every year thousands of houses burn to the ground from chimney fires.

The outdoor bad spots on the chimney should be checked, but are not as serious as problems in the chimney. The most common problems are creosote deposits from too little combustion air or the burning of too much unseasoned firewood. Creosote is extremely flammable when it gets hot in the chimney.

Many houses have small chimney fires from creosote formation and the homeowners are unaware of this. If you’ve ever noticed a sudden surge in chimney draft, it is a sign of a chimney fire. The heat of the creosote burning creates the strong draft.

If there is a creosote fire in the chimney, even a small one, it can damage the mortar and break some tiles. If cracked tiles fall over the chimney and block the air, it will cause excessive smoke withdrawal. You will definitely notice this when it happens.

A more serious problem is the slow deterioration of the mortar between the chimney tiles from repeated minor fires. This can lead to the fact that the fire itself, or just the intense heat, can penetrate the chimney and set the wall on fire. Wall frames can burn for a while before you notice it. If you are asleep and don’t have smoke alarms, it can be disastrous.

Another sign that creosote has built up and there have been some chimney fires is puffy black pieces falling into the chimney. Creosote is a hard material when it’s cold, but when it burns it puffs up and feels like pieces of black polystyrene foam. It crumbles very easily when touched.

If the chimney sweep runs up and down the chimney with brushes, the bloated creosote will definitely be let go in the event of a fire. After cleaning, the entire length of the chimney is checked with a small video camera. Every mortar joint and tile can be carefully checked this way.

Before renting a chimney sweep, ask if they’ll do a camera inspection that you can watch. Be skeptical if the chimney sweep immediately alerts you that you need a new chimney lining without a camera inspection. Installing a new chimney liner, especially some of the newer techniques, can cost thousands of dollars.

Once the chimney has been professionally cleaned and no internal problems have been identified, external and cosmetic problems can easily be repaired by yourself. Professional chimney repair products are available in smaller quantities for do-it-yourself. When working on a roof or high up a ladder, always wear a harness attached to the structure and have a helper support the ladder.

You may think that bricks and mortar are very hard, but they let water through. For years, moisture outside can penetrate the mortar and damage it, as you have noticed in some places. This is most common in regions with many freeze / thaw cycles in winter.

Use a chisel and hammer to tap the suspected bad mortar stains. It’ll come off easily when it’s bad. Fill the pits with a special plastic-based mortar repair compound that matches the color of most mortars. Then spray or brush the entire fireplace housing with liquid water.

If the mortar is damaged, the chimney top is likely to have problems too. This is the top that the chimney will pass through. As with the mortar, cut off the bad crown stains and fill them with compound. Finally, coat the entire crown with a thin layer of compound. Special compounds are available for use in winter, which harden under freezing temperatures.

Up there, check the condition of the metal flashing between the chimney and the roof. If it’s not badly rusted, which needs replacing, coat the grout with a flashing compound and paint the flashing one.

Q: I added a room to my house. It’s efficient with thick attic insulation and a little more is left over. Is it important to have the same degree of insulation in the attic over the existing rooms?

A: It is not critical to have the same insulation throughout the attic. However, more insulation is always better. Even if you can’t cover the entire attic above the existing rooms, cover as much as you can with the extra.

For the second layer, it is best to use an uncoated fleece insulation. If the leftover fleece insulation has a vapor barrier, cut slits in it with a knife. Otherwise moisture can be trapped between the old and the new insulation layer.

• Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit

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