Adding a chimney pot is a great way to increase updraught and prevent excess rain, leaves, animals, and debris from entering your chimney. In certain situations, chimney pots can often be installed without a liner. This guide will walk you through the steps for safely installing a chimney pot on an existing masonry chimney without needing a chimney liner. 

Before you start

When working on a roof, safety should always come first. Here are some tips to keep in mind:

  • Wear protective gear, such as goggles, gloves, and a hard hat secured with a chin strap. Safety harnesses are also recommended for steep roofs. 
  • Ensure ladders are secure, and consider using scaffolding for better roof access. Have someone assist you and help pass up materials. 
  • Prepare the roof surface by clearing loose debris and securing tools so nothing slides off the roof while working. Rope everything down for extra safety. 
  • Check the weather forecast. Avoid this in high winds, rain, lightning storms, or other hazardous conditions. 
  • Know your limits! If the chimney height or pitch of the roof makes you uncomfortable, hire a professional. Safety first. 

Materials you’ll need

  • Chimney pot (match style and size to existing chimney)
  • Mortar mix (3 parts sharp sand to 1 part cement, mixed to wet consistency)
  • Concrete board or slate pieces 
  • Trowels for mixing and applying mortar 
  • Lump hammer for breaking slate
  • Cold chisels and hammer drill for removing old mortar
  • Angle grinder with stone cutting blade (for removing old pot if needed)
  • Mess containment sheets
  • Gloves, goggles, hard hat with chin strap
  • Removing the old chimney pot 

If a chimney pot is already in place, you’ll need to carefully remove it first. These can be extremely heavy, so take precautions. Have someone watch the fireplace area as you work in case debris falls down the chimney. 

First, tap around the edges with a lump hammer to loosen the old pot. Apply gentle pressure in different spots to create stress cracks, then break the pot away into small sections, working from the top down. Make sure each section is securely lowered down before breaking away more. 

For tall pots, you can use an angle grinder with a stone-cutting blade to cut the pot into more manageable pieces, working from top to bottom. Wear a mask to avoid inhaling dust. 

Using a hammer drill, bolster chisels, or hand tools, remove any remaining loose mortar or debris from the top of the chimney and sweep the surface clean. The goal is to expose the flat brick or stone surface at the top of the chimney stack. 

Preparing the surface

With the old pot gone and debris cleared, you should have a flat surface at the top of the chimney. This area needs to be prepped to support the new chimney pot. 

You have two main options for creating a secure base:

Slate pieces

This traditional method involves mortaring cut slate pieces onto the surface around the flue opening. Break or cut slates into approximately 15cm squares using a bolster chisel and lump hammer. 

Apply a layer of mortar around 2cm thick on the chimney surface and press in the slate pieces, keeping a gap in the centre around the flue opening. The slate should fully contact the mortar and chimney surface underneath. The central hole should be slightly smaller than the base of the chimney pot, providing a snug fit. Don’t restrict the flue size needed for proper ventilation. 

Concrete board

You can also use a 12mm calcium silicate concrete board for a neater look. Cut a hole in the centre with a jigsaw, then secure it to the chimney surface using construction adhesive (no nails). As with the slate method, maintain a gap for the flue slightly smaller than the pot’s base. 

Whichever approach you use, check that the new pot sits level and stable on the prepared surface before continuing. 

Installing the new pot

Now for the fun part! Mix a batch of mortar to a wet, sticky consistency—dry enough to stay put but wet enough to seal. We’ll use this to set and seal the new chimney pot. 

Set the pot on the prepared surface and do a test fit. The base should sit flat with no wobbling or rocking. Use spare pieces of slate or concrete board as shims to stabilise the pot if needed. 

With the pot centred atop the flue hole, begin applying mortar. Work some mortar between the pot's base and the slate/board surface to adhere and eliminate gaps. Next, mortar is applied around the outside of the pot on a 45-degree slope, working upward in sections. 

As you add mortar, gently press down and slightly twist the pot to help the mortar stick and prevent air pockets. Continue until the surface beneath the pot and the surrounding area up the sides is fully coated with mortar. Smooth and shape this “flaunching” mortar using a trowel for a neat finish. 

Let the mortar fully cure for at least 48 hours before using the chimney. Keep an eye out for cracks in the mortar that could allow water in. 

Safety first!

To review, here are some essential safety tips:

  • Never work on a roof in wet, icy, or windy conditions
  • Use safety harnesses where required
  • Clear debris from the work area and put rope tools in place 
  • Have someone available to assist you
  • Wear protective gear at all times

And remember—if in doubt, call a professional! Proper chimney maintenance is about safety. Complex jobs or chimneys in poor repair may require installing a liner before adding a pot. When in doubt, contact a certified chimney sweep. 

We hope this guide gives you a good overview of the steps involved in safely adding a chimney pot without a liner. Just be cautious and put safety first for all roof work. 

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