Flue for extension (Black)

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:

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?
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 Twin wall 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 Twin wall pipes?
No Stovepipe, only twin wall flue +£0.00 500mm Stovepipe at the stove +£0.00 1m Stovepipe at the stove +£0.00 1.5m Stovepipe +£0.00
3How high must the twin wall flue be?

Step 1: Determine the required distance between the stove (or stove pipes) and the gutter of the house.

Measure or calculate this distance.

Step 2: Determine the required height of the flue above the gutter.

Within 600mm from the ridge: The flue must terminate a minimum of 600mm above the ridge.

More than 600mm from the ridge: The distance between the cowl of the flue and the adjacent roof/wall/structure should be greater than 2.3 meters.

For the height above the gutter, this translates to:

Pitch of the roof Height on the roof

25° 1m

30° 1.3m

35° 1.6m

40° 1.9m

45° 2.3m

50° 2.7m

Step 3 Calculate the total height of twin wall flues needed

Add these two lengths together and round up to the nearest half, or full meter.

What is the height between the stove (or stove pipes) and the top of the flue
1m +£0.00 1.5m +£0.00 2m +£0.00 2.5m +£0.00 3m +£0.00 3.5m +£0.00 4m +£0.00 4.5m +£0.00 5m +£0.00 5.5m +£0.00 6m +£0.00
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

What will be the distance between the outside wall of the house, and the flue
Wall Support 50 -75mm +£0.00 Wall support 50mm -150mm +£0.00 Wall support 150mm - 250mm +£0.00 Wall support 250mm - 350mm +£0.00
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.

What kind of roof do you have on your extension?
Normal house tiles: Lead flashing 0 -25° +£0.00 Normal house tiles: Lead flashing 25 - 45° +£0.00 Flatter tiles and slates: Aluminium - rubber flashing (45° maximum) +£0.00 Metal roof, non tiles roofs: EPDM flashing (45° maximum) +£0.00
6What 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 +£0.00 All Weather Cowl +£0.00