Fireplace Mega Deals information articles regarding the general preparation and the fitting of the hearth are two articles covering these important steps, intended to be read in conjunction with the following. Therefore this information assumes that you have reached the stage once the fireplace hearth has been fitted.
Now the foundation is in place you can build the body of a marble or granite fireplace having a wooden surround (as in a fireplace package). So, what’s next? Well, if it is to be an inset fire there will be a small drop directly behind the hearth that will need filling and levelling to the same level of the hearth. Some of the mortar mix that is left over from bedding the hearth will do this. Roughly level out the mortar with a trowel and then have a length of smooth straight wood (similar to a spirit level) available. Be careful don’t use anything that could leave scratches on the surface of marble. Place the straight edge against the hearth and into the opening and then in small forwards and backward movements, slowly move from one side to the other across the mortar area. This will then leave a level continuation of the hearth providing a floor for the fire to sit on
Fine, you are now ready to fit the back panel section.
Measure the width of the panel and mark the centre on the top edge. This will line up with the fireplace centre line on the wall. With a trowel cover the back of the panel with ‘blobs’ of tile adhesive (not the whole of the surface). It should resemble the look of snow balls that have been thrown and stuck to it, with gaps in between each one of approx 75mm. Depth of the blobs will be approx 10-15mm at the deepest point. Now stand the back panel on the hearth and gently push the back panel against the wall so that the centre lines up with the centre line. You should feel the adhesive spread slightly and begin to grip. The panel should now be sat further off the wall than its final resting position, measuring approx 30-35mm from the wall.
Here’s the secret to achieving a perfectly flush fit with the back panel against the surround. This is achieved by using the surround itself when lifted onto the hearth to push back the panel into position. When all the back edges of the surround touch the wall and will not move any further back, this is exactly where the back panel needs to finally sit. It’s better if two persons are available to do this to check all back edges are back against the wall at the same time. Take the surround off the hearth now and fill the gap around the whole perimeter of the panel with tile adhesive and smooth off. The same needs to be done around the cut-out in the back panel. Wipe off any excess that is on the surface and ”hey presto” it’s time for a brew!
Question: Hey! Go on then , … “ What if I want an inset fire and only have a flat wall or a shallow pre-cast flue”?
O.K. … The majority of wooden surrounds will have a 25mm rebate which allows for the 20mm thickness of the back panel to be accommodated within the surround. In addition a removable rebate section (known as an adjustable rebate) that can be unscrewed to allow for a rebate of 75mm if required. The 25mm rebate would be used for a fireplace installation against a chimney breast where the depth required for an inset fire would be sufficient, or against a flat wall for an outset/ freestanding fire. In the case of an inset fire with a depth of let’s say 170mm and intended for fitting into a pre-cast flue (with a restricted depth e.g. 100mm) the larger 75mm rebate would be required. Thus, allowing for a deeper fire to be used by bringing the back panel to the front of the surround rebate. The fire depth then is partly sat within the fireplace not just the flue.
Question: “On Yeah!” .. “I did that and now the back panel is so far away from the wall it can’t be supported”
Well spotted. So you can now see that the method of installing the body of the fireplace will depend on the intended fire/flue depth. Everyone knows you can’t hide a 10ft pole in a 6ft hole. So, the back panel will need a frame for it to be fitted against.
When a frame is required for the back panel you will need some lengths of approx 50mm x 50-80mm rough sawn timber for this. The marble or granite back panel is normally 20mm thick and you need to fill the 75mm rebate. Caution; The plastered wall you are fitting against will almost certainly not be perfectly flat across the whole fireplace area. In my experience the best walls come somewhere close, others have a bow, dip or worse. These fluctuations have to be taken into account if the surround is to fit as tightly as possible to the wall when the job is completed. To compensate you therefore need to leave space for a flexible bed of tile adhesive.
To simplify this then, there is the thickness of the back panel 20mm plus a timber frame let’s say 50mm giving a total of 70mm. This provides for a 5mm tolerance gap within the 75mm rebate. On a problem uneven wall, a plaster skim is possibly required to improve the surface as no fireplace material bends to fit the wall.
The frame dimensions are the same as that of the back panel and containing as many support pieces to support the panel and importantly the fire cut-out. This will be dependent on the width of timber used (if 50mm wide, more struts than if 80mm wide). The frame is measured against the centre line then fixed to the wall with 75mm screws. The tile adhesive is then applied to the whole of the timber rather than to the back panel. If a gas fire is to be fitted, it is necessary to clad the timber along all three surfaces of the cut-out with a non combustible fire board. Caution; Remember to allow for the thickness of this board when constructing the frame so that the fire opening size is maintained .
All measurements given are as a general guide and should be checked for relevancy.