FIREPLACE BOARDS

Fireplace board is an intermediate layer designed to help focus the heat in the furnace, which well improves the profitability and efficiency of the fireplace as a whole. To prevent your fireplace from being a significant source of heat loss, it's necessary to insulate both the top and bottom inside the chimney. 

It is important to install an air barrier behind it after installing insulation but before the fireplace is installed.

All fireplace boards should carry an A1 fire classification, ensuring non-combustibility and high fire resistance and have high resistance to continuous heating within the range of 700-1100°C.

WHAT BOARD TO USE IN FIREPLACE?

In a fireplace, extremely high temperatures are reached, often up to 1000 degrees Celsius, and never less than 600 degrees Celsius. Therefore, fireplace boards need to withstand high temperatures of up to 1100°C near the fireplace. They should also be easy to work with, relatively heavy, and allow for screwing in. Most fireplace boards have excellent heat resistance and strong stability.

One of manufacturers is PROMAT®, known for their flagship boards such as PROMAFOUR, PROMATECT®-MST, PROMASIL-1000L, PROMASIL®-1100 SUPER offering protection up to 1100°C, and another company called Vitcas® with its Vermiculite fire-proof insulation board.
Below you can find a table comparing these products.

*The information provided in the table is for informational purposes only, and Insulationgo LTD does not take any responsibility for the data presented. Please note that the information provided in the table is subject to change, and it is advisable to consult the manufacturers or experts for the most accurate and up-to-date details regarding the products. Please note that the prices and specifications mentioned in the table are subject to change.

Fire boards for Wood Burning Stove/Log Burner | Comparison table

WHAT IS THE BEST FIREPLACE BOARD? / WHAT IS THE BEST MATERIAL FOR INSIDE FIREPLACE?

As seen above, all boards are A1 classified, indicating non-combustibility. Weight, affecting fireplace quality, is notably higher for Promat PROMASIL 1100 SUPER, at 16.20kg/m². For a cheaper alternative, consider Promafour, 4kg lighter per m². 

Regarding density, PROMAFOUR leads at 970kg/m³, indicating potential durability. PROMATECT®-MST follows at 750kg/m³. PROMASIL-1000L and PROMASIL®-1100 SUPER share a density of 300kg/m³, while Vermiculite Insulation Board sits at 600kg/m³.

Temperature resistance spans from 1000°C for PROMAFOUR, PROMATECT®-MST, and PROMASIL-1000L to 1050°C for PROMASIL®-1100 SUPER, with Vermiculite Insulation Board reaching 1100°C.

Thermal conductivity is lowest for PROMASIL-1000L at 0.163W/mK (800°C). PROMAFOUR follows at 0.180W/mK, while PROMATECT®-MST is at 0.22W/mK. PROMASIL®-1100 SUPER leads at 0.125W/mK (800°C).

Fireplace weight per square meter: PROMATECT®-MST is lightest at 10.78kg/m², PROMAFOUR at 12.3kg/m², PROMASIL-1000L at 16.00kg/m², and PROMASIL®-1100 SUPER at 16.20kg/m².

Firepalce sizes: PROMAFOUR is 2400mm x 1200mm, PROMATECT®-MST is 1200mm x 2500mm, PROMASIL-1000L and PROMASIL®-1100 SUPER are 2500mm x 1200mm, and Vermiculite Insulation Board is 1000mm x 610mm.

Fireplace prices: PROMAFOUR at £190, PROMATECT®-MST at £440, PROMASIL-1000L at £490, and PROMASIL®-1100 SUPER at £520. Vermiculite Insulation Board is the most affordable at £36.
 

WHAT TYPES OF SCREWS ARE SUITABLE FOR SECURING FIREPLACE BOARDS?

Fireplace boards can be nailed or screwed. The screws used for fireboards should maintain their structural integrity at the temperatures necessary for fire testing. Typically, screws are made of steel, which melts at around 1370°C. Therefore, the screws used for installing fireplace boards should withstand high temperatures, with a melting point not lower than 1200°C. Additionally, these screws should have a tensile strength of approximately 1300kg due to the considerable weight of the fireplace boards.

ALTERNATIVE MATERIALS FOR FIREPLACE BOARDS

If purchasing fire boards doesn’t fit your budget, consider using alternative, more affordable materials such as stone, brick, or cement. These materials are naturally non-combustible and can endure extremely high temperatures. We discussed this further in the article titled 'BEST HEAT RESISTANT BOARD FOR WOOD BURNING STOVE / LOG BURNER'.

CAN YOU PAINT STRAIGHT ONTO FIREBOARD? 

Only a few fireboards are suitable for direct painting. Some fireboards have a smooth, closed structure, making it challenging to paint them directly. However, there are boards that can be painted, such as Promat Promafour and Promat Monolux 800. Their smooth sanded finish allows proper adhesion and retention of paint. The paint used for fireboards should be a heat-resistant paint rated to withstand temperatures generated by the fireplace, creating coatings resistant to high temperatures up to 1000°C. It should exhibit good adhesion to the surface and mechanical durability.

It is not recommended to apply paint when there is a consistently high temperature around the fireplace. Painting should be done at room temperature, around 22°C. A very good and advisable idea is to do this in summer when you can open windows and ventilate the room thoroughly. After the paint has dried, it should undergo a curing process. This means gradually heating the fireplace to a relatively low temperature for the first 5-6 hours and then gradually increasing the temperature each time the fireplace is lit.

IS CEMENT BOARD OK FOR FIREPLACE?

When considering whether cement board can be used for a fireplace, attention should be paid to its resistance to continuous heating. Cement boards generally lack the ability to withstand prolonged exposure to high temperatures compared to boards specifically designed for this purpose. Therefore, they are not used for fireplaces. Their low resistance to continuous high temperatures could result in bending towards the heat source and consequently, deformation and cracks at the joints. Additionally, cement boards contain reinforcing fibers that may self-ignite in very rare situations. Cement boards are not available in thicknesses greater than 15mm, which further eliminates their use as fireplace boards.

FIRE RATING CLASSIFICATION

The fire resistance is always expressed in minutes, usually in classes that are multiples of 30 minutes. Before you choose your product, it’s important to understand the classification process and what each level means in terms of fire resistance and protection. The BS EN 13501-1 classification comprises three ratings. The first is the main Euroclass rating, which will be the letter A1, A2, B, C, D, E or F. A1 is the highest level of performance, while F is the lowest. Flooring materials are followed by the abbreviation ‘fl’ (for example, A1fl). Linear pipe thermal insulation products are followed by the abbreviation ‘L’ (for example, A1L). A1 products are classified as non-combustible. A2 products are classified as limited combustibility, and B to F are classified as combustible in ascending order. The second classification relates to smoke emission during combustion. This is indicated by a rating of s1, s2 or s3, from highest to lowest performance. Smoke emission classifications are not provided for products with an E or F overall rating. The third classification relates to the level of production of flaming droplets/particles during combustion. This is indicated by a rating of d0, d1 or d2, from highest to lowest performance. E-rated products receive a d2 flaming droplet classification. F-rated products receive none. A1-rated products are not given smoke emission or flaming droplet ratings, on the assumption that they make no contribution to fire growth or spread. Occasionally, a building insulation product may focus on a Class 0 or Class 1 rating. However, these classifications do not indicate the combustibility of the product, referring only to limited surface fire performance characteristics. Class 0 is a rating defined in Approved Document B of the Building Regulations 1991. It combines two tests in the British Standard BS 476. The first assesses a surface’s contribution to fire propagation (BS 476-6) and the second assesses the spread of flames across a surface, including distance and time (BS 476-7). Class 1 is a limited classification based on the test in BS 476-7 only. It is important to recognise the limited application of these classifications.

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Picture credit:https://basc.pnnl.gov/resource-guides/walls-behind-fireplaces#edit-group-scope

Video credit:https://www.youtube.com/watch?v=PDiaoxkD3pU