Installing a twin wall flue

A twin wall flue, installed properly

A twin wall flue is the backbone of any stove installation without a usable chimney. We install channels in 316 stainless steel with 25 to 30 millimetres of insulation and a G rating, tested against a soot fire of 1,000 degrees. The flue is installed in just 1 working day, certified and with an inspection report.

Through the roof or along the facade, for a pellet stove or wood burner: you receive 1 fixed price upfront for the entire project.

The flue determines draft, safety, and insurance compliance: this is not a place for compromise, but for a proven system.

How we install your flue

1. Step 1: measurement and route determination

   We visit your home for free, measure the route, and determine the optimal path together. As straight as possible, with a maximum of 2 bends, because every bend reduces draft and adds 30 to 90 euros.

   You will immediately see where the flue will run, inside and outside, and what finishing details are required.

2. Step 2: penetration and installation

   The penetration through the wall or roof receives proper fire separation with 50 to 80 millimetres of clearance according to the G-value. We then build up the flue using wall brackets every 1.5 to 2 metres, perfectly level and using clamps from a single system to ensure every connection is gastight.

3. Step 3: terminal placement according to regulations

   For new installations, the flue terminal extends at least 1 metre above the roof ridge, equipped with a storm collar and rain cap. This ensures full compliance with local regulations and delivers reliable draft in any weather.

4. Step 4: inspection, test burn, and certification

   We measure the draft, conduct a test burn, and issue the certificate required by your insurance provider and manufacturer warranty.

Through the roof or along the facade?

Both routes have clear advantages. Through the roof provides optimal draft and costs 1,750 to 3,000 euros, as detailed in our guide on flues through the roof. Along the facade requires no roof penetration and costs 1,500 to 2,800 euros, see the layout of an external facade flue.

We recommend the route that best suits your property and heating appliance. High-level installations are carried out by our own team using professional safety equipment, without third-party roofers or subcontractors. If you have concerns about an existing installation, we can also inspect it independently of a new installation.

How much does an installed twin wall flue cost?

Expect 80 to 120 euros per metre for materials and 1,500 to 3,000 euros for the complete job, including wall/roof penetration, finishing, and 500 to 900 euros in labor costs. If your home is older than 10 years, a reduced VAT rate of 6 percent applies instead of 21, saving you 300 euros on a 2,000 euro flue excl. VAT. All individual component prices are listed in our itemised price breakdown.

Common mistakes we prevent

Most flue issues stem from improper installation: mixing components from two different brands that fail to seal, excessive bends causing draft restriction, penetrations lacking proper fire separation, or a terminal positioned too low. Each of these mistakes costs hundreds of euros to fix later, and severe errors can void your home insurance coverage.

Materials we stand behind

We only install CE-marked systems with temperature class T400 or higher and a G rating, made from 316 stainless steel designed to withstand corrosive flue gas condensates. This comes with a 10-year system warranty and an expected lifespan of 25 to 30 years. We archive all certificates and system specifications in your file, ensuring seamless warranty support years down the line. Read more about the standards on the Buildwise standards page.

Suitable for which appliances?

For wood burning stoves, we install flues ranging from 150 to 180 millimetres, while pellet stoves typically require 80 millimetres, often using a concentric system. If you are unsure about your existing masonry chimney, installing a flexible chimney liner is often the smarter and more cost-effective option. Discover our full range of solutions on our flue and chimney services page.

Your itemised quote

You will always receive a fully itemised quote: flue length per metre, every bend and penetration listed separately, with labor and finishing details clearly broken down along with the applicable VAT rate. This allows you to compare quotes easily and know exactly what you are paying for upfront.

This transparent approach is part of our stove and flue quotation service, offering a fixed price within 48 hours of measurement. Standard components are kept in stock, meaning installation usually takes place within 2 to 3 weeks of approval.

Common scenarios

A frequent request is upgrading an open fireplace with an insert or freestanding stove: the oversized flue is lined to match the diameter of the new appliance, as explained in our fireplace conversion service. We also regularly line chimneys when purchasing a new home, following an inconclusive inspection report, or when connecting pellet stoves to existing masonry chimneys.

Homebuyers frequently rely on our report and certificate during property transactions, allowing you to start the heating season safely in your new home. If you rent out property, the certificate serves a dual purpose: providing instant proof of your legal maintenance compliance as a landlord.

If you are unsure about your setup, our camera chimney survey provides complete clarity within an hour, complete with footage you can view alongside us.

After installation, flue upkeep is minimal: 1 annual sweeping service costing 60 to 90 euros and a quick check of brackets and sealant every 2 years. We can automatically schedule this as part of our annual combined maintenance service.