Fire pits in the garden are enjoying increasing popularity. To ensure that it works safely, heat-resistant stones, such as those listed below, should be used when laying them out.
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differences in heat resistance
There are some heat resistant rocks that are suitable for a backyard fire pit . But be careful, because here a distinction is made as to whether it is direct or “surrounding” heat that affects the stone material. The term “direct” is used to describe that where the fire burns and the highest temperatures occur. The “indirect” area is around the fire and constitutes the boundary of fire pits to keep it from spreading uncontrollably. Lower temperatures prevail in the indirect area, which is why a different stone material is suitable here than for direct firing.
Danger of non-heat-resistant types of stone
If non-heat-resistant types of stone are used, there is a risk that they will crack, melt or burst due to the high temperatures and due to their porosity due to moisture absorption. The fire’s control border becomes obsolete, allowing it to spread and pose a real risk to life and property. If the stone material bursts, it can become a projectile projectile and cause fatal head injuries. Therefore:
- only use stone material that can withstand heat
- absolutely avoid gravel, pebbles, limestone and aerated concrete blocks
Fireproof earthenware
Where the fire is ignited (direct heat), only three types of stone are suitable due to their enormous heat resistance of at least 1000 degrees Celsius:
Clinker
Clinker or hard burnt bricks, as they are also known, are among the types of stone with the highest heat resistance. They tolerate temperatures of up to 1,300 degrees Celsius. They also have a high density, which means that only minimal moisture is absorbed. They are available in different colors so that they can also have a decorative effect on a fire pit.
firebrick
Fireclay brick is manufactured specifically for use in incinerators such as fireplaces. This type of stone is made of refractory ceramic material with clay and aluminum oxide. This composition ensures heat resistance of up to 1,250 degrees Celsius. This makes the fireclay brick ideal for the interior of fireplaces, which can be bordered with more decorative types of stone.
bricks/bricks
The bricks/bricks fired from clay are very fireproof due to this fire. Temperatures of 1,000 degrees do not bother them. If you want it to be even more heat-resistant, you can add simple fireclay mortar. An important advantage of bricks and bricks is that they do not retain heat. The chance that they will ignite again after the fire has been extinguished is therefore very low. In addition, the transfer is simple. The smooth surfaces are great for conjuring up a durable fireplace that is easy to clean. However, they only have a low strength and therefore break quickly. Careful handling during storage and processing is therefore advisable.
Heat resistant outdoor stones
If a fireplace is set up correctly, temperatures in the immediate vicinity of the fire will usually not exceed 800/850 degrees. In order to select the right stones, it is therefore important to ensure that they are sufficiently heat-resistant. A total of eleven types of bricks have this in addition to the refractory bricks already mentioned.
Heat-resistant stones from B to G
Basalt/Basaltlava
Basalt rock, and basalt lava in particular, is an effusion rock and a product formed from the molten rock (magma) of a volcano. It is logical that this demonstrates high heat resistance. With a heat tolerance of up to 1,000 degrees Celsius, basalt lava gravel in particular is ideal for framing a fireplace. With dark black, gray and grey-blue tones, they also provide a decorative accent. Pure basalt stone has a slightly lower density due to the pressing, but is still suitable as a heat-resistant border.
Gneis / Gneisto
Gneiss, also known as gneisto, is a type of rock best known to miners. There it is called “sparks” because of the glittering effects. These are rocks that become metaphoric rock as a result of pressure and/or temperature increases and reach the surface of the earth as a result of erosion or erosion. This type of stone has similar structures to granite, but proves to be immensely more resistant to cold and heat. They are available in grey, white and black. Depending on the viewing angle and the incidence of light, they sparkle and thus ensure a stylish view of fireplaces.
Granite
Granite, which is mainly used as flooring and kitchen worktops, is particularly hard due to its high density. Granite rock is predominantly quarried from the earth and contains mainly quartz and feldspars. The heat-resistant rock is not outstandingly fireproof, but it does not cause any problems up to 600 degrees Celsius. It can therefore only be used to a limited extent as a border outdoors and should in any case be far enough away from the direct influence of heat so that the 600 degrees are not exceeded.
greywacke
As a natural stone, greywacke is mainly used for paving stones. This is characterized by an enormous density and the gray to green-grey colouring. Due to the mainly contained quartz and feldspar parts, there is a heat resistance of up to 700 degrees Celsius.
Heat-resistant stones from M to Q
marble
As a carbonate rock, marble is also a heat-resistant type of stone, which can, however, be used to surround the fireplace in the garden. Marble withstands temperatures of up to 600 degrees without any problems or damage. Garden owners expect further advantages with the use of marble in fireplaces:
- Optical setting of noble, exclusive accent
- Easy to clean up after a fire
- Very durable/durable
- weather resistant
- Cold-Insensitive
porphyry
A volcanic rock is porphyry. Like basalt/basalt lava, it therefore also has a high insensitivity to heat. If it contains a high proportion of quartz, the porphyry stones are fireproof up to 1,000 degrees Celsius. It convinces with its high robustness, which makes the stone very durable. Only the appearance is to be regarded as simple and therefore without any significant decorative value.
Quarzit
In contrast to the simple porphyry, quartzite presents itself as a natural stone in “living” colors ranging from red to rainbow colors. If you like it less conspicuous, you can opt for the gray version. There is a visual resemblance to marble. Quartzite is the hardest rock that currently exists.
As the rock name suggests, the rocks consist mainly of quartz. In addition, other rocks are included that are heat-resistant like quartz. The stones tolerate temperatures of up to 600 degrees Celsius well. It should only be ensured that they do not come into direct “contact” with the fire.
Heat resistant stones from S to T
sandstone
Sandstone is one of the cheapest types of stone to put around a fireplace. However, it should consist of at least 50 percent sand grains and quartz. Only then can it be regarded as a heat-resistant type of stone that can easily withstand temperatures of up to 700 degrees.
soapstone
Soapstone is best known for its use in sculpting. In the garden, the stone made of talc can also be used for the fireplace. Since the minerals cristobalite and enstatite are converted at temperatures above 800 degrees Celsius, temperatures above the 600 degree mark should not be exceeded in order to preserve the soapstone properties. Soapstone is particularly popular because it fills fireplaces with colour. It is available in:
- White
- Rosa
- Rot
- green
- Blue, blue-green
- Schwarz
Trachyt
A very widespread stone used for hot locations is trachyte. It is also known as an oven stone because it was used for this centuries ago. As a plutonite, there is a similarity to granite, but the trachyte has a significantly higher heat resistance of up to almost 1,000 degrees Celsius. It is just as insensitive to cold, so it is ideal for permanently installed fireplaces if you spend the winter in the garden.
Tuff
Like trachyte, tuff is a stone found in old ovens. However, it must not be exposed to direct fire, so that it can only be used as a border at temperatures of around 700 degrees.c
