Chimney pots are made from clay, and are then fired in a kiln to make them resistant to the heat from the smoke and fumes that will travel through them when in use.
Replacing a chimney pot requires a tall ladder, and a head for heights - if you are in any doubt at all, the you would be wise to pay a roofing contractor to carry out the work for you.
Fitting Your Chimney Pot - Selecting the correct chimney for your roof
If there is an existing chimney pot you will need to measure the external dimensions at the top and the bottom of the chimney (as many styles of chimney pots taper inwards from the bottom up), and the height of the chimney pot, so that you can purchase a direct replacement, which will not only look right but will also be easier to fit as you will be replacing like-for-like.
If you are fitting a new chimney pot you need to take into account the ratio of the opening at the top of the fireplace to that of the top opening of the chimney pot, which needs to have a ratio in the range of 1:8 to 1:10 (the top of the chimney pot needs to be smaller than the opening at the top of the fireplace).
Also, you need to ensure that the internal dimensions of the base of the chimney pot that you are looking to purchase should always be equal to or greater than the external dimensions of the flue.
Replacing a broken chimney pot
If you are replacing an existing, damaged or broken chimney pot you will need to completely remove what is left of the existing pot, and any mortar holding it in place.
You will need to be very careful, as chimney pots can be surprisingly heavy - many older pots were manufactured from very substantial clay and subsequently can be disarmingly heavy. This is further increased if a clay flue is installed.
It will be a tricky job to remove the chimney and the mortar holding it in place (assuming that it is still fixed in position) and you will then need to carefully and safely get the broken pieces down to ground level.
Fitting a new chimney pot
- Firstly, carefully lift the chimney pot up to the roof - the safest way to achieve this is by using a length of rope to haul it up.
- Attempting to carry the chimney pot up the ladder is unwise and should not be attempted.
- Once the new chimney pot is up on the roof it should be placed over the flue opening in the chimney stack, which will allow you to judge if the base will correctly fit.
- If the base of the pot does not match the size of the opening, pieces of slate can be used to narrow the opening, which will provide a secure base for the chimney pot.
- Using a 3 inch (75mm) layer of mortar (made from four - rather than three - parts of soft sand to one part of cement to reduce the risk of mortar failure) around the flue opening, bind the base of the chimney pot into the mortar, pressing firmly into place once you are happy with the position of the pot.
- Dampening the area around the base of the pot, any slate used over the flue opening, and the stack stops the mortar from drying out too quickly and gives you longer to make adjustment to the positioning of the chimney pot.
- Once the chimney pot has been correctly positioned you need to taper the mortar away from the base of the pot using a trowel, at an angle of approximately 45 degrees, to allow rain to run off - this is known as 'flaunching' the base.
- You should then leave the pot, and not use the fire, for 24 hours to allow the mortar to set, and then it should be inspected to confirm that there are no cracks in the mortar or fissures that could allow water or bird ingress.
Maintenance of chimney pots
Chimney pots require very little maintenance other than an inspection every 5 years or so to check it for cracks and to ensure that the mortar is also in good condition and that the chimney is still held securely in place.
Our chimney pots are manufacturered by W T Knowles, whose expertise and knowledge is credited back to 1906.
Where can I purchase chimney supply near me?
About Roofing Supplies stock a wide range of clay & metal chimney pots, cowls, chimney caps & chimney flues to prevent drafts and encourage airflow. To discuss pricing and the availability of chimney supplies, please call us on 01737 763008 or email us here.
You can view and order chimney supplies in any of our branches listed below or we can deliver nationwide: