Every circumstance you may encounter cannot be addressed here but in general terms the following would apply to installation of a marble or limestone fireplace including fireplace packages (hearth, back panel & surround). As with most projects the finished result depends almost entirely on the preparation. Mistakes made at this early stage when installing a marble fireplace can be costly to rectify or even at best impossible to hide.
Imagine your fireplace installed, you rest in front to admire your efforts and then you realise the fire sits slightly to one side, or say, the hearth is not centred or maybe not quite level. It’s only maybe a centimetre or so (although I have seen much worse) – you then ask yourself … will anybody notice. You just have and you will know something is not quite right possibly every single time you enter that room. My experience tells me that this seems acceptable to some, “bang it in – jobs a good un”. If you would like to do a job to be proud of, you may like to read on and get some information which will perhaps avoid some of the costly pitfalls.
O.K. … This assumes that you have carefully chosen your intended fire, decided on the look that appeals to your taste from a wide selection of fireplaces. Also, that all the components are entirely suitable for their intended use. This is particularly important with regard to solid fuel fires.
Well done! … A major stumbling block overcome.
Let’s get started then. This will require the decision maker in the family – You know who this is!
Where in the room is the fireplace to be situated?
At this stage I should flag up a major note of caution!!! Regulations in force regarding solid fuel fires and all gas fires exist for your safety. These are enforceable with severe consequences against any individual who is not wholly competent regarding installation. A registered Hetas installer in the case of a solid fuel appliance or Gas Safe engineer should be consulted to ensure all regulations are met (for example: balanced flue/fan flue gas fires, proximity to opening windows, walls, distance to a fence etc.,).
If a chimney breast exists (internal or external) you will probably be restricted with regard to where the fireplace can be sited. For instance, if a fire is to be inset into the chimney breast then this will be dictated by the builder’s fire opening. When against a flat outside wall without a flue and a balanced flue gas fire or fan flue gas fire is to be fitted, bear in mind both of these have an external flue projection. Take a walk outside the room and check that a soil pipe or other fittings are not going to prevent installing such a fire in the desired area, particularly if alongside a driveway. Again you should have this information confirmed when consulting a registered installer. The accessibility of a gas connection should one not already exist can also be established in the case of a gas fire.
Hey! Question: “What if my property has a pre-cast flue” I hear some saying! …
Well, you are likely to be restricted considerably more than having a chimney breast. The dimensions of the flue opening would dictate the size of the fire this type of flue would accommodate. These vary greatly, some are narrower and also some deeper than others. A modern property may well have the purpose built large fire opening which will take most inset gas fires. On the other hand, some older properties will have been built intending only to use this type of flue with an outset gas fire. The centre of the fire opening has also to be the centre of the fireplace if using the available inset width and depth. Should you not require the gas flue as an electric fire is to be used, then ignore the flue and position your fireplace where desired.
I have deviated slightly from the installation of the fireplace preparation, but you can no doubt appreciate that the type of intended fire and/or if the flue needs to be in use will determine the positioning of the fireplace. O.K. that’s enough about flues and fires, Phew!
Now , find your pencil and tape measure it’s time the centre line is drawn. Every measurement is taken from the centre line. If you have decided on the centre of the room, then a vertical line using a builder’s level can be drawn from the floor to somewhere above the height of the finished fireplace. If against a chimney breast then find the exact centre and do likewise. Next establish the width of the fire (If to be inset). The majority of fires fit into a standard ‘cut-out’ in the back panel of the fireplace being 40-42cm, wide 56-57cm high. Two vertical lines 21cm each side of the centre line can now be drawn. The horizontal line will depend on how high the hearth stands which needs to be added to the 57cm high cut-out. A standard hearth is approx 6-7cm but allow for a mortar bed (more on this to follow) so you would make the line at approx 8cm plus 57cm = 65cm from the floor. You will now have the outline of where the fire will sit through the back panel. Ideally the opening will mirror these dimensions and project to the back of the flue at this size or as close as possible. If the opening is smaller, then some alterations have to be made otherwise the fire will not fit. If the opening is too large then the back panel will not be supported sufficiently and there would be a risk of the marble cracking from the heat.
The next step is to mark out the hearth, the foundation stone of the fireplace and care must be taken to get this step right. Mark the wall from the centre line (for a standard size hearth 1370cmm/54”) 685mm each side of the centre line. If there should be any floor coverings such as thermo-plastic tiles on a solid floor it is advisable to remove these in the area the hearth will sit down onto. Otherwise when you lay the mortar for the hearth the tiles will possibly lift . It is better to allow the mortar to adhere directly onto a solid concrete floor. All lumps and bumps left from the removal of a previous installation need to be taken off as a bump could prevent you from levelling the hearth both ‘side to side’ and ‘back to front’.
Hey, wait! Another question: “I’m told my property has a floating floor, what now?”
O.K. without getting too technical in regard to building techniques, a floating floor is found in modern properties as a means of insulation. The floor is suspended and then a layer of polystyrene sheet approx 5-7cm thick is laid onto the sub-floor. Sheets of chipboard then form the surface of the floor. I would suggest that this is not a good surface in which to install a heavy fireplace onto. The area where the hearth is to sit should be marked out and the chipboard and insulation removed down to the sub-floor. This is easily done, but bear in mind that gas or central heating pipes can be in this area so don’t cut deeper than the thickness of the chipboard. Once the chipboard is removed the insulation can easily be cut with a hand held blade and removed safely. Next you will need to mix a sharp sand and cement mix [almost dry, 5 parts sand to 1 cement] and level off to the existing floor height. This will give you a solid surface as with a solid floor which will eliminate problems arising in future.
Earlier I mentioned that an allowance should be made for a mortar bed under the hearth. This will depend on the floor covering preferred once the fireplace is installed. If carpet and underlay then allowing for this thickness under the hearth will result in being able to see the full height of the hearth once the carpet is fitted.
This article is provided as a guide only and all dimensions given should be checked against the relevant component sizes being installed.