Opening up a Fireplace

If you're lucky enough to find the home you are renovating has a blocked-up fireplace, ready and waiting to be brought back into use, then you'll be pleased to know that the job of opening it up to make way for a new fire or stove can usually be tackled by an able DIYer. Bricked-over fireplaces are found in many older houses, after the advent of central heating in the late 1950s and early 1960s meant the use of gas and electricity became a convenient alternative to solid fuel. Many people blocked up their fireplaces to make way for modern fires.

In recent years, the fireplace has re-emerged as a design statement, and many renovators have unblocked the openings and once again made the fireplace the focal point of the room sometimes bringing the chimney back into full use; sometimes just installing a decorative fire.

In most cases it will be obvious whether or not there was once a fireplace in your house: in most pre-1939 houses there will be a chimney breast with alcoves to the side; houses from the 1950s often had the flue built externally, so that will also be visible.

Assessing the job

If you're unblocking the fireplace simply for aesthetic reasons, then the absence of a chimney is no problem; otherwise a working flue will be needed. If you believe the chimney may have been removed, look in the loft for either a flue, or else signs of it having been removed: there will usually be chopped-off bricks and a sooty strip. In either case, you will need the flue and chimney to be reinstated if you intend to install a fully functioning fire.

It is also important that you get an expert to find out whether the fireplace was blocked because of a fault as opposed to modernisation.

DIY do or don't?

Smoking Fires: Smoke leaking from the fireplace into the room is caused by insufficient draw from the chimney or down draught. Generally, a warm or taller chimney, a larger cross-sectional area of the flue and a smaller fireplace opening increase draw. A modern rule of thumb is that the open area above the burning surface of the fire should be no more than six times the cross-sectional area of the flue, although some old fireplaces appear to work perfectly well with ratios up to 12, and well-built inglenooks greater still.

Whether you can attempt to open it yourself, or if you need the help of a builder, will depend on how the blockage was made. If the wall has been completely rebuilt, you need to call in a builder. Likewise, if there is no lintel in place, or if the one there is cracked, you could risk the wall collapsing if you knock through yourself.

Also, check to see if the hearth is still in place by lifting the floor covering. This is usually a concrete slab about 125mm deep that extends beneath the fire and out into the room. If missing, this will need to be rebuilt. Before installing a new appliance, you must get a chimney sweep to clean and inspect the flue (see www.chimneyworks.co.uk).

Do I need consent? Generally, any alterations to fires and fireplaces are classed as building work, and you should contact your local authority before starting any work. If you live in a listed building, you will probably need listed buildings consent. Call the conservation officer in your local planning department for advice. This doesn't apply to Conservation Areas.

Building regulations: Approved Document J now states that bringing a flue back into use or changing the use of a flue requires the person doing the work to carry out certain tests to ensure the suitability of the chimney. This certification should only ever be carried out by a professional.

DIY Guide

Opening up an old fireplace is a relatively simple task with only the most basic of tools required: a lump hammer, a cold chisel or a 2¼ bolster, and a couple of builders buckets are the only tools that are needed.

Firstly, protecting the floor immediately in front of the fireplace, and covering furniture etc. is always recommended, as soot is especially awkward to remove from furnishings.

Start by carefully chopping off the plaster from the assumed middle of the fireplace, working outwards. This way the outline of the opening will become apparent without the removal of unnecessary plaster.

The opening will probably be spanned by a lintel. Starting one course down from the underside of the lintel, carefully remove a full course of masonry the width of the opening. This is the hardest part but once removed all the other masonry should come out easily. At this stage, a small opening with a fireback where the fire used to burn should be revealed, and if in good condition can be left undisturbed for future use; but if this masonry is defective, a dog, hob-grate or a larger fireplace is being fitted, it will need to be removed and the original builders opening exposed. This structural opening can be quite large in pre-Georgian houses, but gradually reduced in size to no more than three foot square in modest Victorian homes, and smaller still more recently. It is into this space that all fireplaces are fitted.

Remove further plaster exposing the outline of the structural opening together with its arch or lintel. All the masonry within will require removal, and once cleaned out will leave a square opening capable receiving the fireplace or stove of your choice.

A few basic checks need to be carried out at this stage. A defective lintel or arch will need rectifying. The chimney needs to be sound and clear of obstructions which can range from birds nests and general debris to recently fitted pipework and cables, and, most importantly, any flue or chimney capping removed. Sweeping the chimney completes the task.