This selection guide is for black steel flue pipes extending outside of a house's extension.

Click on the product in the "your selections" box to view details of the chosen product. Once you add this list to the shopping basket, you can make changes such as adding or deleting products.
Note: This wizard is designed for situations where the flue is within 2.3m from the house; in this case, the flue must extend higher than the roof. If the flue is further away than 2.3m, you can utilize this wizard

1Diameter of the flue:
125

WOODSTOVES & MULTIFUEL STOVES: The flue legally needs to be a minimum of 6" (150mm) in diameter if you are burning wood or coal. Unless when you install a DEFRA approved stove with a 5" flue outlet, in which case you can use a 5" liner (125mm).

What diameter of flue do you need (mm)?
125 150
The ideal flue size is typically determined by the exhaust outlet of the stove or appliance. It shouldn't to be smaller than the appliance exhaust hole.

The Building Regulations (Document J, page 30) require that the minimum flue size for stoves are as follows:
- Up to 20kW burning smokeless fuel - minimum 5" - 125mm diameter.
- Up to 30kW burning any fuel - minimum 6" - 150mm diameter.
So the regulations recommend a minimum flue size of 150mm for any stove (on which wood could be burnt) unless it is Defra Exempt.

OPEN FIRES including flame effect open gas fires:
Minimum 200mm diameter for fire openings up to 500mm x 500mm. Larger fires require a flue area equal to 14-16% of the total area of the fireplace opening. (Minimum flue diameter 180mm for gas effect fires).
2Stove pipes inside the house? Or everything with isolated pipes?

There are two ways to build your flue:

Only twin wall flue pipes

- No dangerous hot pipes in the room.

- Esthetically more pleasant.

- Better draw.

Single wall and twin wall pipes

- A single wall flue radiates warmth into the room ( this does reduce the draw somewhat as well).

- These stove pipes can be used up till 450mm under a flammable roof (150mm for a non combustable roof).

- Single wall pipes should stay 450mm from flammable walls and other flammable materials (unless sheilded like on the picture).

Stove pipes inside the house? Or everything with isolated pipes?
No stove pipes, only isolated pipes +£0.00 500mm stove pipe on the stove +£30.00 1m stove pipe on the stove +£38.00 1.5m stove pipe on the stove +£68.00
3How high must the twin wall flue be?
For a flue in an extension, the height of the flue depends on its distance from the wall and nearby structures. Here are the key points to consider:

If the flue is within 2.3 meters of the wall or any nearby structure:

The flue must terminate at least 1 meter above the roofline or any opening (like a window or door) within that 2.3-meter radius.

If the flue is more than 2.3 meters from the wall or nearby structures:

The flue can go straight up, but it should ideally be a minimum of 4.5 meters in total height to ensure proper draught and functionality (in practice 3 meters may be enough)

Flat Roofs:

If the extension has a flat roof (pitch less than 10°), the flue must terminate at least 1.8 meters above the roof surface if the roof is combustible.
What is the height between the stove (or stove pipes) and the top of the flue?
0.94m +£165.00 1.38m +£248.00 1.88m +£286.00 2.32m +£369.00 2.82m +£407.00 3.26m +£490.00 3.76m +£528.00 4.20m +£611.00 4.70m +£649.00 5.14m +£732.00 5.64m +£770.00
4What is the distance Wall to Flue?

This distance determines what wall support to use.

Normally the cheapest solution is to take a wall support 50 -75mm. However in case of an overhanging roof, you may want to use another wall support

When the distance is more than 350 mm, there is no wall support for this. If the height above the roof is more than 1.5m; you need a Roof Stabiliser Bracket to support the flue. In practice, this will only work for a flue with a distance from the wall of more than 1.5m (if it is less, the flue needs to end above the gutter; you can not stabilize that with a roof stabilizer bracket)

What will be the distance between the outside wall of the house, and the flue
Wall support 50-75mm, up to 3m along the wall +£27.00 Wall support 50-75mm, 3 to 6m along the wall +£54.00 Wall support 50-150mm, up to 3m along the wall +£80.00 Wall support 50-150mm, 3 to 6m along the wall +£160.00 Wall support 150-250mm, up to 3m along the wall +£89.00 Wall support 150-250mm, 3 to 6m along the wall +£178.00 Wall support 250-350mm, up to 3m along the wall +£95.00 Wall support 250-350mm, 3 to 6m along the wall +£190.00
5What kind of roof do you have on your extension?

The choice of the flashing depends upon:

- What kind of material material is covering the roof, and

- The pitch of the roof (0° being a flat roof, 60° a sharp roof)

Automatically we add a roof support and -when required- a storm collar.

Rubber flashings come in two versions. Choose by the total length of the flue below the roof. Up to 4m, the flue is still hot where it passes through the roof, so it needs the version for flues up to 4m. Longer than 4m, the flue has cooled down more, and the version for longer flues is used.

What kind of roof do you have on your extension?
Normal house tiles: lead flashing, 0 - 25° (lead colour) +£166.00 Normal house tiles: lead flashing, 25 - 45° (black) +£209.00 Flatter tiles and slates: aluminium and rubber flashing (0 - 45°), flue up to 4m below the roof +£170.00 Flatter tiles and slates: aluminium and rubber flashing (0 - 45°), flue longer than 4m below the roof +£121.00 Metal or other non-tiled roof: rubber flashing (0 - 45°), flue up to 4m below the roof +£95.00 Metal or other non-tiled roof: rubber flashing (0 - 45°), flue longer than 4m below the roof +£88.00
6Height of the flue above the roof

Will the flue stand more than 1.5m above the roof?
No, 1.5m or less above the roof +£0.00 Yes, more than 1.5m above the roof (roof stabiliser bracket) +£125.00
7What kind of Cap is required?

There are 2 types of cap to choose from:

Rain cap
Will keep vertical falling rain out of the flue. In case of side winds, rain will enter the flue. In case of a flue outside this is less of a problem, as it will not floote into the house.

All weather Cowl
Keeps rain out of the flue. Also blocks downwinds from entering your flue. Downwinds come from higher objects in the vicinity (up to 10mtr), and without this Cowl they will blow the smoke back into your house.

What kind of Cap is required?
Rain cap +£80.00 All Weather Cowl +£113.00