Vermiculite Fire Bricks

Why do I need fire bricks?

They are fitted to the stove for insulation purposes, allowing your stove to burn efficently but also acting as a heat barrier and preventing the flame from reaching the steel stove walls.

When should I replace my fire bricks?

A hairline crack in the brick will not damage your stove.

Replace the brick if;

the hairline crack causes the brick to fall down
you can see the steel body of the stove through the crack
or if you notice crumbling on the edges of the bricks, that exposes the steel

It is advisable not to light your stove if the steel is visible. If your throat plate brick has fallen down, don’t use your stove as it will distort the metal throat plate, that holds the throat plate brick in place.

If you have any of the Stock Cube family of stoves or the Penguin 7 or 78 series, they have vermiculite bricks on the base of the stove. The same advise applies to these bricks. These are all wood only stoves, so smokeless fuels should NOT be burnt in them. We advise that you retain a layer of wood ash, approx. 2 cm deep on top of the base bricks. Wood ash acts as an insulator, it will protect your bricks. Occasionally you may notice that wood ash can “cake” on top of these bricks, this may be to do with moisture in the fuel. If you are removing this for an annual service take care that you do not damage the brick as you do it. Scraping and poking the bricks can damage them.

How can I make my bricks last longer?

We have a few tips on how you can make your bricks last longer:

Do not use over sized logs in your stove. Cramming logs that are too big into your stove can cause damage to your stove, causing you to replace the firebricks more often
Do not overfill your stove
Ensure you only burn seasoned wood, see point below about moisture
Where possible, place the logs into the stove rather than throwing or dropping them. This reduces the shock absorbed by the firebricks, thus making them last longer
If cleaning your stove internally do not use water or water based cleaning agents, vermiculite will weaken if it absorbs moisture. Equally if you have drips coming down your chimney this can happen.
If you have vermiculite bricks on the base of your stove, take care extra with tools and logs

What are they made from?

Vermiculite bricks are cut from a pressed board. They is common misunderstanding that they are fired ceramic brick or a quarried stone. This is not true. Vermiculite is a naturally occurring mineral formed into board and then cut into shapes. Not only does it work hard during its lifetime but when you have finished with it you can put it on your garden and it will degrade in to the soil. It an aluminium-iron-magnesium silicate.

Signs to look for to see if you need new fire bricks?

Cracks are caused by impact or vibration, often simply a log/solid fuel thrown in a little roughly or the door squeezed shut on an oversized log. Crumbling on the edges or corners is a sign that the vermiculite is beginning to degrade and is ready to be replaced. How long it lasts will depend on how much the stove is used, under average seasonal evening usage this will usually be years.

Pinking; if the bricks change to a noticeable pink shade, this is sign that the stove has been over-fired, or burnt at excessive temperatures for a prolonged period of time.

One of my fire bricks is broken/damaged. Should I replace a single fire brick or the whole set?

When your fire bricks need replacing, we recommend buying fire bricks in sets for the following reaons:

It is easy to damage a neighbouring fire brick during the process of replacement. It is easier to have spare fire bricks to hand, rather than having to wait for a re-order to arrive.
They can be stored for future use when required. When ordering a set of fire bricks, only replace the one that has broken, not the whole set. Keep the rest in store for future replacements.
It is usually cheaper to buy fire bricks in sets rather than on their own. The postage and packing can be the same for a single or a set.

Bricks are available on their own, should you wish to only purchase a single replacement brick.

Protect the steel body