Victorian Fireplace Reproductions
Cast iron fireplaces from the 18th Century, 19th Century and 20th Century
How to fit a cast iron fireplace insert with a marble or slate mantel
Marble and slate mantels tend to come in several separate pieces ( legs, frieze and shelf ).
The outside return is the depth of the mantel leg on the inside.
The inside
return is the depth of the mantel leg at the fireplace opening.
If you stand a mantel flat against a wall the gap on the inside where the insert
fits between the mantel and the wall is a measure of the rebate usually about
1-3" for cast inserts.
Marble or Slate mantels are fitted against the brickwork, not on top of the plaster and fixed with bonding plaster.
You should first check that the interior opening of the mantel is slightly less (when assembled) than the exterior size of the insert. Otherwise you will have a gap to hide when the fireplace is fitted as the mantel is almost always fitted in front of the cast iron insert.
The plaster must be removed to beyond the extremities of the shelf and ouside returns of the mantel
Standing the fireplace insert together with the legs of the mantel will enable you to measure the size of the opening that you need to make in the wall or chimney breast to accomodate the cast insert.
You should now be able to measure the size of the opening that you need to make in the wall in order to accomodate the fire insert. If the mantel has a large rebate you will need to remove less material to accomodate the insert.
Not forgetting to allow for the thickness of any hearth that is being fitted, mark the size of the necessary opening on the wall and make the hole using a lump hammer and bolster chisel
If you stand a mantel flat against a wall the gap on the inside where the insert
fits between the mantel and the wall is a measure of the rebate usually about
1-3" for cast inserts.
If the fireplace is to be fitted on top of the hearth, the thickness of the hearth must be allowed for in assessing how big to make the hole to accomodate the fireback as it will usually raise the fireplace by 2-3 inches.
For many original cast inserts it will be necessary to fit a lintel to support the central section of chimney breast. In many Victorian houses in England, the brick arch that was usually fitted around the 38" high level, is still intact and will often do.
It can be noted that many Victorian and Edwardian houses in the UK have a standard builders opening built into the chimney breast during the original construction that is usually around 38" square by 14" deep (or the depth of the chimney breast)
If there is a piece of skirting board fitted try to remove it intact or cut it around the centre of where the fire opening will be and remove it in two pieces.
Once you have made the space in the chimney breast (or on a flat wall if the chimney is on the outside wall of the house) it is a good idea to put down the hearth into its central position and do a dry run, assembling the mantel and insert in position on the hearth. You should check that there is a clear path for the fumes and smoke from the firebox to escape up the main flue.
If the plaster has been removed or has fallen off the wall at the points where the outside of the mantel touches it, this should be replaced. The space immediately behind the hearth can be now filled up to the same level as the hearth with mortar or broken brick etc with a mortar layer over it.
Cast Iron inserts should be fitted to the brickwork so it is best to remove the plaster to at least the extremities of it (usually about 38" square)
If everything now looks correct remove the fireplace and fix the hearth in place by bedding it on a thin layer of sloppy mortar about 1/4 "- 1/2 " thick should be adequate. The gaps around the edge of the hearth will need to also be pointed using the same mortar.
If the cast iron insert is the type that have tile sets incorporated in them, the tiles must be fitted before the fireplace is put in and cannot be easily changed afterwards. Both original and repro cast iron inserts will have some form of tile carrier or a bar behind where the tiles fit.
The easiest technique for fitting the tile sets (usually five 6" tiles on each side) is to start at the bottom and wedge each tile in turn using cardboard or wooden wedges. Bonding plaster should then be plastered all over the back of the tiles and the tile carriers or bar. After about half an hour this should be hard enough for the insert to be fitted
The next step is to put the insert with its cast back attached into position, central on the chimney breast normally, and hold it in place with the mantel, making sure that the mantel is flat against the wall and that the insert is pulled forwards to meet the inside returns of the mantel.
If the fixings for the mantel are mirror plates you should mark the position of the central holes in them on the plaster.
If the cast iron insert has a separate fireback . (clay fireback or ceramic fibre-back ) this should be put into the opening before the insert is put in place and pulled forward to meet it after the mantel has been fitted and before the job is back filled
DIAG
Gently remove the wooden mantel leaving the fireplace insert undisturbed. Drill and rawl-plug the marked holes for fixing the wood mantel to the wall.
If the gap between the outer edges of the insert and the brickwork is around 1- 1/2" or less the insert can be sealed in this position by the use of bonding plaster. It is important to dampen the brickwork with water or a water PVA mixture first as very dry brickwork will absorb the moisture too quickly from the interface between the plaster and brickwork and will not adhere.
It the gap is larger than this it must be bridged using non combustible materials. A quick way is to cut bricks and build up to a few inches below the top of the insert at the sides. Then a lintel must again be used across the top. The essential point is that a gas tight seal must be achieved all around the two sides and top of the insert, right down to ground level
The wooden mantel can now be fitted by screwing it to the previously sited rawl plugs.
Any space behind the fireback must now be filled with non combustible material such as broken brick. The space should be filled level with the top of the fireback at the front edge and should slope up at the back and sides. Any soot which falls down the flue should roll into the fire opening rather than collecting on a shelf where it could ignite causing a chimney fire.
The loose rubble should be capped off using weak mortar ( 7 parts sand to 1 part cement ) and if a rear flap or damper is to be fitted this should be installed before the cement has hardened and checked that it can move freely.
With cast iron fireplaces there is usually no need to worry about
the interface between the fireback and the insert fascia as when heated up
the cast fascia will expand together with the back, be it fired clay or cast
iron. Fire cement can be used to fill any gaps between back and fascia.
If you stand a mantel flat against a wall the gap on the inside where the
insert fits between the mantel and the wall is a measure of the rebate usually
about 1-3" for cast inserts.