Fitting an All Tiled Fireplace with Push-to Hearth
The following is a guide based on my experience of fitting our Fireplaces. It is just one man's ideas and should be in no way taken as law. If this guide seems long winded it is because making mistakes when installing a Fireplace can have disastrous or even fatal results.
If you have any doubts about local building regulations or the installation of your Fireplace, competent builders, chimney sweeps or chimney lining specialists can generally be taken as a good source of information and advice.
The flue is the technical term for the usually vertical shaft that draws the smoke and fumes from the Fireplace to the terminal. The terminal is the exit point for the smoke, usually a chimney pot.
Before you buy a new Fireplace and definitely before installing the Fireplace it is strongly advised that you check the flue for soundness. It must not leak. Leakage may be potentially life threatening. If smoke is getting anywhere other than the chimney associated with it then have it checked by an expert.
The usual method for testing a flue is the smoke test. Although there is nothing to stop you doing this yourself, I would always advise that an experienced person carry this out. Fireplace fitters, builders and especially chimney sweeps may be the best way forward. If you find a local chimney sweep in your yellow pages he will clean your chimney, which is always a good thing to do when fitting a new fire, and should also be able to do a smoke test to check the flue for soundness .
Smoke tests are basically very simple. A smoke pellet is burned in the fire opening. Smoke should emerge from the correct terminal only (usually one chimney pot). This is a good indication that your flue is sound. However, many houses have had their flues messed around with at some stage and there is no substitute for seeing the bristles of a chimney-sweeps brush poking out of the top of a chimney pot!
While the smoke pellets (which are deliberately strong smelling) are burning, you should check all of the rooms that the flue passes through, including the loft space. There should be no leakage into any of the rooms above or below where the fire is to be fitted.
As a rough guide, houses built before World War 1 (1914) are quite likely to have leaky flues and must always be thoroughly checked. Also in my experience, wood or coal fires will damage the flue much more than a gas fire. Many houses built after World War 2 tended to have gas fires fitted and so the flue will probably still be sound. However, since house builders were a mixed bag of variously qualified people, all flues should be checked prior to the installation of any Fireplace
If there is any leakage, sweeps can be very helpful. Good builders should also know how to repair the damage and there are specialist flue fitting firms who do nothing else but fix leaky flues.
If you find yourself confronted by a solid brick wall where you think the Fireplace used to be, remove the vent or knock a hole in the wall to enable a smoke check to be done on the flue
If the smoke stubbornly refuses to rise up the flue it may be because it is capped off at the top. Capped flues must be uncapped to do a flue smoke flow test. However, it may just be that the flue is filled with moist, cold air. This air will be heavier than that in the room and prevent the smoke from rising. Warming the flue with a blowtorch or burning some sheets of newspaper inside it will often do the trick of getting the smoke moving up the chimney, enabling it to be checked.
The constructional hearth is the patch of fireproof material (either a concrete, stone or tiled surface) in every wooden floored house that should appear flush with the floorboards in front of where the fire is to be fitted. If this has been removed for some reason and you are fitting a Fireplace to burn solid fuel (coal or logs) it must be adequately replaced before starting to fit the Fireplace.
The constructional hearth is there to stop the joists of the floor extending beneath the Fireplace. If they did, then they would dry like tinder and any small ember finding its way down to them from the Fireplace would cause a much larger fire than you ever intended. A constructional hearth will usually consist of fireproof material at least 6" deep, around 48" wide and extending out approximately 18" .
Houses with chimney breasts.
A good start when fitting any Fireplace is to check whether the chimney breast is plumb and if the floor in front of it is level using a spirit level. In many older houses this may not be the case. Fitting a Fireplace level and plumb on a chimney breast that is not looks dreadful. It is easy to pick up a difference in level of 1/4 a bubble on a spirit level, so I would suggest that you fit the Fireplace exactly as crookedly as the existing chimney breast.
Ground floor Fireplaces are almost always fitted central to the chimney breast. Bedroom Fireplaces may be fitted off centre as several different flues may rise up inside the same chimney breast. Ensuring that every Fireplace could be fitted centrally was not always a priority for house builders
Mark the centre of the chimney breast on the wall. Position the Fireplace against the wall and move it to a central position. Draw roughly round the Fireplace on the wall and then move it out of the way.
Use a lump hammer and bolster chisel to remove all the plaster inside the line that you have drawn. Then make the hole that is to take the fireback and the throat forming lintel. This hole should be approximately 20" wide x 28 " high x 10" deep. If the hole is already bigger than this or gets bigger as you bash away with your lump hammer and chisel don't worry.
Try to leave about 2.5" of fireproof material at the bottom (brick etc.) to allow the fireback to sit level and about 2" higher than the floor level.
Sit the clay fireback loosely into the hole that you have just made. Put the Fireplace up to the wall again in exactly the position it needs to be fixed at.
Mark the position of the two fixing lugs on the Fireplace and the spots on the wall where you will need to drill the two holes to fix them.
Temporarily fix the Fireplace to the wall or get someone to hold it securely for you. It should be seated flush against the bare brickwork of your chimney breast.
Pull the fireback forward until it sits snugly against the two lengths of fire rope that we attach to the back of the Fireplace opening tiles, squashing the fire rope between the Fireplace and the fireback. The fire rope is attached by a small amount of fire cement all along its length.
The fire rope is there to provide a compression joint between the fireback and the opening tiles of the Fireplace.
The small gap it makes is your expansion gap which allows for movement as the fireback gets hot.
Wedge the fireback securely in place.
Remove the Fireplace from the wall and lean it out of the way. Drill two holes in the brickwork where you marked the position of the lugs and insert a rawl-plug in each hole.
Things should now look roughly like this
Without disturbing the position of the fireback (this is crucial) lay bits of brick and mortar to meet the side of the fireback. A good dollop of mortar to the floor of the fireback will also level the internal space and help secure it in place.
The throat forming lintel sits on the fireback and makes the throat of the Fireplace. The lintel is shown here UPSIDE DOWN to show the shape.
The lintel has two purposes. One is to support the brickwork above it. The other is that the shape avoids turbulent airflow up the chimney. Turbulent rather than smooth airflow can cause fumes to come back into the room.
The flue pull is mainly determined by the volume of the flue. The restriction caused by the throat gives a balance between heat loss up the chimney and air flow to remove smoke and fumes.
Fit the throat forming lintel to the top of the fireback so that it sits flush with the front face of it and has the sloping edge facing the sloping top of your fireback. Fill the space behind the fireback with non-combustible material (a good way of getting rid of the bits of brick and plaster that you have produced so far.)
You should backfill to slightly above the level of the fireback and slope the infill up to meet the back wall of the fire opening. This is so that any loose soot etc. falling down the chimney will fall into the fire opening and not collect above it. Any collected soot can burn and cause chimney fires.
Cap off this slope neatly with a mix of weak mortar (about seven parts sand to one part cement) and fit the throat forming lintel onto the top of the fireback as shown. Then brick up any gaps in the brickwork above the lintel.
Put the Fireplace to the wall one last time and fix it with two screws through the two lugs. The fireback should be 2" off the floor and fitting neatly against the back of the Fireplace opening tiles. The fire rope should be squashed between the fireback and the back of the opening tiles. The small gap left (approximately 0.25") is your expansion gap which allows for movement as the fireback gets hot. This gap should not be grouted or filled with mortar or the opening tiles may crack.
You should now use a sponge to dampen the wall around the outside edges of the Fireplace and plaster in the gap between the Fireplace and the brickwork. At this point the small gap between the front of the throat forming lintel and the Fireplace can also be filled in with a handful of mortar.
The push to hearth can now be fitted by laying a thin (about a quarter of an inch) bed of fairly sloppy mortar on the floor in front of the Fireplace and gently sliding the hearth up to the face of the Fireplace.
Finally, grout in the gap between the Fireplace and the hearth with the same coloured grout as used on the Fireplace (usually white) a bit of which can be supplied on request. Neatly fill in the gap between the hearth and the floor with mortar.