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Breaking out and excavating a fireplace


A “builder’s opening” or “original fireplace”, is at the foot of almost every chimney flue and is of a pre-determined size (you get what you are given). Do not confuse a small open fire with the builder’s opening, small open fires are often built within the builder’s opening and excavation will reveal the larger recess.

You can sometimes work out the size of your builder’s opening prior to any excavation work but not always (more on this in “breakout”). It might be possible to go larger than the builder’s opening but you are then likely entering the territory of the experienced professional builder.

A house might have more than one builder’s opening. If a house has two pots then it will have two flues and two builder’s openings. If it has four pots it will have four flues and four builder’s openings (e.g. two downstairs and two upstairs). Builder’s openings, especially in bedrooms, are often bricked/boarded up and plastered over.

Fireplaces never share flues: each builder’s opening has its own flue all the way to its own pot.

Pic 1. This small fireplace is NOT the builder’s opening – it is built within the builder’s opening. The stone you can see in this pic is just cladding (although there is stone behind in this case). See pic 2 and 3 for the same fireplace being opened up to the builder’s opening.

Pic 2. In stone properties the builder’s opening is often MUCH larger than the small fireplaces often present.

Pic 3. A very nice end result. The large inglenook is the builder’s opening. Don’t expect something this size in brick properties and even stone buildings can have small builder’s openings.

 Another two examples below:

The scene after removing a gas fire: a small recess that was once a small open fire.

The same fireplace opened up to the builder’s opening. This was in a small suburban brick-built bungalow and is a very large builder’s opening.

This customer was not quite so lucky. The size of a builder’s openings vary from house to house.