I recommend this article to those determined enough to create one of the crowning features of their home: the fireplace. I would like to take this opportunity to remind all readers that I am not a professional fireplace builder, so the materials and techniques I describe come solely from research and not professional experience. Simply put, everyone should use these instructions at their own risk!
Steps Before Construction:
- First, gather as much information and imagery as possible, and decide exactly what and how you want to create. (shape, color, etc.)
- Ensure your chimney is properly sized and perfectly positioned.
- Select a fireplace insert.
- Knowing the dimensions of the insert, we can begin the design work. Let’s create many drawings and take measurements! At the same time, we can start the time-consuming task of selecting the cladding. This is important because it lets us foresee how much work the fireplace cladding will require, and whether we can craft the dreamed-up mantel section. Incidentally, it also helps us determine if we can bring the envisioned design to life using the chosen material.
- Based on the plans, procure the materials (Ytong, adhesive, stones). I used Murexin adhesive and grout, trusting the factory data and others’ experiences, which say they can withstand temperatures up to 800oC. I couldn’t find this information for other adhesives.
For my 9kW insert, a 200mm chimney was pre-installed.
Let’s keep quality in mind!
Construction:
Before beginning construction, mark the fireplace’s location and key lines on the floor and wall.
Then start building by gluing the first Ytong blocks to the floor. With every Ytong block placed, it is essential to check both the level and vertical alignment!
First Steps
The base must be made solid enough, as it will support everything – approximately 400-500 kg. The visibly wide base was also necessary because underfloor heating pipes run beneath the fireplace, as no space was originally left for a stove or fireplace during construction. !!Only do this if you have seen the thickness of the concrete and insulation during construction!!
The recessed section of the ash shelf has also been designed. The wall will be protected from heat by a 5 cm thick Ytong. The size of the wood storage was determined by the size of the fireplace insert. Care must be taken with the lintel here to ensure the structure remains stable. That is why I used 10 cm Ytong here. The depth of the recess was determined by the covering material already purchased.
Experience has shown that for the lower lintel, it is absolutely not advisable to use a masonry element thinner than 10 cm due to the risk of excessive heating.
I applied full plastering around the firebox area, as it’s always best to be cautious. Beneath the firebox – contrary to the picture – three pieces of 0.5 cm thick flat iron were added for extra reinforcement. Be sure to use metal anchors when drilling, since this area will get extremely hot!
The full plastering should also be done on the top side of the wood storage if it’s not going to be tiled!
After this, wait a day for the base to dry thoroughly. Only then can the firebox be placed and built around according to the plans. I used strictly 10 cm Ytong blocks. Make sure not to fully enclose the expansion joint rim at the edge of the insert. On my side, about 3 mm was left free on both the right and left, but the cover is still intact. Of course, some recommend even more (5 mm)!
Next to the firebox, about 10 cm of space was left open for the warm air to flow. Make sure to leave enough surface area for the dome and the mantel!
For stability, I also avoided using mitered pieces as lintels, opting instead to purchase a load-bearing lintel and cut it to the right size. (the advantage is that it’s reinforced)
After that, I built in the remaining parts up to the lintel level. Once the work is finished, allow 1 day for drying!
After this, only the tiling remained. The main structure is ready; the Sisyphean task remains: grouting the stones of the windowsill and the edges.
IMPORTANT! Please read the instructions for the tiling material you purchased before you begin! Most smooth artificial stone surfaces need to be moistened before applying adhesive!
Knowing the actual dimensions of the finished building, we imagine and then sketch the kind of dome we want. Since the interior is tall, I definitely did not want anything that reaches the ceiling. The essential point is that it covers the chimney pipe, and its top remains sufficiently distant from the heat. I have read about certain proportions that are ‘supposed’ to be observed, but I was guided by my own vision.
Another reason was that, according to my plans, the rising warm air should exit through the top of the dome. (side grills could have been used here too, but I chose not to)
With safety still a top priority, the dome’s frame was welded from 2×2 cm steel profiles, then fully clad in aluminum sheet to ensure excellent heat distribution. When the sheet is placed on the inside, a 2 cm air gap is left before the final drywall layer. This is also crucial to prevent the dome’s exterior from overheating, especially around the chimney pipe (front panel).
The fire-resistant drywall covering is installed on the exterior side, along with the perforated grille on top of the frame.
The dome has no back because it needs to be removable for chimney cleaning, which is required every 2-3 years! Instead of a back panel, I attached a 2mm thick aluminum sheet to the wall, positioned 0.5 cm away from the wall’s surface. Mineral wool can also be used here, for example.
After that, I fully primed the dome with Dryvit adhesive, then tinted it with Dryvit noble plaster. Finally, the chimney pipe was installed in place, and we mounted the now heavy dome.
Tip: it’s best to have the flue pipe custom-made from quality material. The pipe in the picture is made of 2mm stainless steel, and it includes a butterfly valve to restrict airflow if the draft becomes too strong.
Also, once the final dimensions are known, it’s time to envision the type of lintel wood we want. Important!! When designing the dome, be sure to leave a proper rim to support the wood! We chose the solution shown in the picture, knowing that hardwood tends to warp. True, but I didn’t want pine.
As a final step, let’s treat the eyebrow beam and the windowsill stones so that the ash can be easily washed off later.
Once everything is ready, let’s conduct a test with a newspaper! If the chimney is working well and the smoke doesn’t flow back, we can even light a fire, since the paint needs to be burned off.
According to my measurements, the dome heated up to about 50°C. The efficiency is excellent; after a sufficient time, the outer stones warm up pleasantly, and the warm air escapes through the top of the dome as expected, without overheating it excessively. After cooling, I checked for thermal expansion. There was only a small crack in the grout at one spot where the tiling stone touched the edge of the fireplace opening. This can be fixed afterwards.
I wish everyone good work and great success!
IMPORTANT: The fireplace size, based on the volume of air, might not necessarily require external air intake, but if a range hood or gas stove is present in the same space, it is crucial to ensure some form of safety vent—especially with plastic window and door frames. I didn’t have any problems because, due to the stove, a ventilation duct had already been installed in the ceiling earlier.
The covering materials come from Pilisvörösvár, sourced from the stone shop located by the railway crossing.
Execution, text, photos: Zsolt Béres
TL;DR – Brief summary
(Open the arrow if you can´t see it!)
Once you know the dimensions of the firebox insert, you can start designing. Based on the air space, my fireplace would not necessarily require outside air, but if there is an extractor fan or gas stove in the room, it is essential to provide some kind of safety vent.
