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Here is an extensive guide on how to fit or replace a chimney pot. Chimney pots are traditionally made of clay or ceramic, however more advanced heating systems have become popular, with most new build houses offering alternative heating options such as central heating systems. Chimney pots are found mostly on Victorian style buildings, though we still see chimneys today on modern homes due them now being seen as a detailed exterior feature. With chimneys adding appeal to a home we have listed below a step-by-step guide on how to fit a chimney pot.
If you are adding a chimney to a home with a centre chimney there are rules which need to be taken into account before installation. One of the most important aspects of installing a chimney is the ratio of the fireplace opening to that of the top opening of the chimney pot. The ratio needs to be in the range of 1:8 to 1:10. The base dimension of the chimney pot should always be equal to or greater than the opening dimension of the flue.
If you are replacing a broken chimney pot you will need to completely remove the top of the chimney. Old styles of chimney pots can be very heavy so care should be taken when removing the chimney pot. It’s important to take safety steps to ensure the old or broken chimney is safely handled to the ground.
Secure the broken chimney pot in place using ropes or heavy duty tape to prevent more damage caused due to falling.
Using a chisel and a hammer, safely break away the old mortar.
Lift the broken chimney pot from the flue and carefully bring the pot to the ground. Some flue liner may remain poking out the top of the chimney stack. If so, cut the tiles away with a circular saw.
When installing a new chimney pot it’s important to check for any openings. Openings can often allow birds to enter the chimney. A step to take to avoid this would be to cover the opening with stainless steel wire mesh. Once the mesh is in place the steps below will take you through the installation process.
Using strong wiring, seal the mesh to the chimney opening. It is important to secure this firmly. Some people will advise using silicone-based caulk to do so but this is unlikely to be able to take the heat.
When secure, carefully lift the chimney pot to the roof.
Once the new chimney pot is on the roof you should place the chimney pot over the opening. From this you will be able to judge if the base will correctly fit.
In some cases the pot may not match. This may be due to the base shape. By using pieces of slate you can narrow the opening, providing a secure base for the chimney pot.
Dampen the top of the chimney stack and any slate used to narrow the base. This helps lock in the moisture of the mortar.
Spread 3 inches of mortar (made from cement and concreting sand – see note below) around the flue opening, binding the base of the chimney into the mortar. You should then press firmly down on the base of the chimney, bringing a secure hold with the mortar.
Note: For this step to be successful it is important for the ratio of mortar mixing to be one part cement to four parts sand. By using this ratio it helps the mortar to retain moisture, lessening the risk of cracking.
Once the flue opening and chimney pot have got a secure hold. The next step is to flaunch the base. First make sure the mortar is at an angle of 45 degrees.
This procedure can be done by using a dry trowel, tapering the mortar to allow the angle of the flaunch base. The 45-degree angle base prevents water from building up around the pot when it rains. Once your chimney pot is set in place you should leave the pot for 24 hours. After this time you should inspect the chimney pot for any crevices or cracks which may have occurred whilst setting.
It is recommended that a chimney pot should be inspected every 10 years. Key things which often occur are plants growing in the base of the mortar, which can affect the structure of the mortar. It’s also important to look out for cracks and crevices as trapped water could cause damage, especially if it freezes (causing expansion).
This guide has been improved then approved by chimney expert Edward Turner who has been in the chimney industry for over 14 years.