Frequently Asked Questions About Isokern Pumice Chimney Products

What is an Isokern pumice chimney liner?

An Isokern pumice liner is a modular chimney system made from volcanic pumice. Pumice is naturally lightweight, insulating, and heat-resistant, making it ideal for chimney construction.

What are the benefits of pumice chimney liners?

• Excellent insulation — helps maintain flue temperature and reduce creosote formation.
• Lightweight — easier to install than clay or concrete alternatives.
• Durable and long-lasting — resistant to thermal shock and cracking.
• Modular construction — components stack easily and quickly.

Compatible with many appliances — wood, gas, and some multi-fuel systems.

How do Isokern pumice liners compare to stainless steel liners?

Pumice liners are rigid, insulated, and long-lasting, ideal for new builds or major rebuilds.

Stainless steel liners are flexible or rigid metal tubes—better for retrofitting into existing chimneys.

Pumice generally offers superior insulation, while stainless steel offers ease of installation in older chimneys.

Can Isokern liners be installed in an existing chimney?

Yes—if the existing chimney space is large enough and structurally sound. 

Are Isokern pumice liners safe for wood-burning fireplaces?

Yes. Pumice liners are specifically rated for high-temperature wood-burning applications and help maintain steady flue temperature to reduce creosote buildup.

What sizes do Isokern liners come in?

They are manufactured in modular square and round sections offering internal flue diameters of 150mm, 175mm, 200mm, 225mm, 250mm, 300mm, 350mm, and from 400-600mm

Do they require insulation?

Pumice liners require at least 15mm of light expanded clay aggregate (code 130769) is required between the liner and masonry.

How long do Isokern pumice liners last?

They are expected to last multiple decades with proper installation and normal use. Pumice is highly resistant to thermal shock and moisture damage.

Are Isokern chimney systems approved for gas appliances?

Yes— Isokern liners are rated for gas, wood, and solid-fuel appliances. Always check the specific model certification and local code requirements.

How do I maintain a pumice chimney liner?

Have it swept annually by a certified chimney professional.

Inspect for cracks, mortar deterioration, or block shifting.

Ensure the cap, crown, and flashing remain in good condition.

Can Isokern liners improve fireplace performance?

Yes. Their insulation helps keep flue gases warm, which enhances draft, meaning better smoke evacuation and more efficient combustion.

What is the warranty? 

Isokern pumice products are manufactured by Schiedel comes with a 10-year Manufacturer's warranty. 

Standard Warranty: Isokern pumice liners and Double Module (DM) systems are generally covered by a 10-year warranty guaranteeing quality and performance.

Isokern is a well-established brand under the Schiedel product portfolio, and the warranty is provided by Schiedel.

To ensure the warranty is valid, the products must be specified, installed, and maintained correctly.

Swept by a qualified person, such as a HETAS Approved sweep (in the UK).

Used with the correct fuels.