Twin Wall Flue - External - Black-straight

This Selection Guide is for black twin wall flue pipes going outside the house/building.

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twin wall through the house

twin wall flue external

1Diameter of flue liner:

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 liner 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).
2Choose the adapter between stove and twin wall flue
Many wood-burning stoves come with the choice of attaching the flue pipe to either a top or rear flue exit. All things being equal, it’s best for a flue pipe to go up in a straight line in order to achieve the best draw and most efficient burn from your woodburner.

For the adaptor you have the following options:

- Single to twin wall adapter (also increasing adapters)

To be pushed into the stove opening; sits inside the spigot of your stove and then connect to other twin wall flue pipe above. Or push into the stove pipe.

-

- Single to twin wall continental adapter

A continental twin wall adapter creates the easy connection of Twin walled flue pipe to any European model of stove.

This Continental Stove Adapter is to use if you have a European stove collar; as the sizes are slightly smaller than a standard 5" or 6" stove collar.

5" continental adapter: outside of the adapter is 115mm; to twin wall 125mm (5"), and

6" continental adapter: outside of the adapter is 135mm; to twin wall 150mm (6").
What kind of adapter between your stove and the twin wall flue?
Standard adapter 5" to 5 +£0.00 Standard Adapter 6" to 6 +£0.00 Increasing adapter 4" to 5 +£0.00 Increasing adapter 5" to 6 +£0.00 Continental adaptor +£0.00
3Horizontal distance stove - outside flue

The distance can be calculated as: distance = G + E + D

G = distance heart of stove outlet - to- wall
E = thickness wall
D = distance outside wall - to - flue (usually 50mm, but can go up to 350mm in case you want to go along a overhanging roof, without using elbows)

If the distance is fixed (you can not move the stove forward or backward) you will most likely need to use a adjustable flue pipe. You can add this later to your basket.

Together with the T135 piece, we will add:
- the adapter,
- the 45 degree elbow
- the wall sleeve. The wall sleeve is meant to slide through the wall and to be cut to length as required. Add mortar around outside of it or fireproof insulation.
- 2 finishing plates, to cover the opening between the flue and the wall; both inside and outside.

What should be the horizontal distance between the heart of the stove, and the flue outside?
280mm horizontal (490mm upwards ) +£0.00 420mm horizontal (620mm upwards) +£0.00 590mm horizontal (800mm upwards) +£0.00 600mm horizontal (550mm upwards) +£0.00 740mm horizontal (670mm upwards) +£0.00 910mm horizontal (850mm upwards) +£0.00 940mm horizontal (1150mm upwards) +£0.00 1260mm horizontal (1200mm upwards) +£0.00 520 - 630mm horizontal (730-840mm upwards) with telescopic pipe +£0.00 630- 890mm horizontal (850 - 1100mm upwards) with telescopic pipe +£0.00 840 - 950mm horizontal (upwards 1050 -1170mm) with telescopic pipe +£0.00 950 - 1210 mm horizontal (upwards 1170 -1410mm) with telescopic pipe +£0.00
4Flue height outside

Determine what the height (X) of the flue outside should be from the T upwards

Step 1: Determine the required height on the roof (M)
see " Complete information" below.

Step 2: Calculate the total height of the flue (stove to rain cap)

Total height of the flue (Z) = M + L - K
L = Height of the roof
K = Height of the stove

Step 3: Calculate how many meters (X) of straight pipes are needed outside (above the T)

X = Z - V

Z = Total height of the flue (see step 2)
V = height coming from the stove till the T (it is written top right in question 2 " ...."mm upwards")

Check: The total height (Z) from stove to end cap should be at least 3.5 meter.
You do not need to have the exact height, a bit higher higher is also okay.

How many meters straight length (X) do you need?
Straight length: 1.9m +£0.00 Straight length: 2.3m +£0.00 Straight length: 2.8m +£0.00 Straight length: 3.3m +£0.00 Straight length: 3.8m +£0.00 Straight length: 4.2m +£0.00 Straight length: 4.7m +£0.00 Straight length: 5.3m +£0.00 Straight length: 5,6m +£0.00 Straight length: 6.1m +£0.00 Straight length: 6.7m +£0.00 Straight length: 7.5m +£0.00

Chimney Heights and Termination

Simple rules

Within 600mm from the ridge
The flue has to end minimum 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 higher than 2.3 mtr.

For the height on the roof this means:

Pitch of the roof Height on the roof.

25° 1070mm

30° 1330mm

35° 1610mm

40° 1930mm

45° 2300mm

50° 2740mm

All the rules

The minimum chimney height recommended for minimum performance of wood burning and multi fuel appliances is 4.5 m from the top of the appliance to the top of the chimney. In practice you 3.5m is often enough.

The distance between the cowl of the flue and the adjacent roof/wall/structure should be higher than 2.3 mtr.

Within 600mm from the ridge: Flue has to end minimum 600mm above the ridge.

The diagram below, taken from Document J (building regulations), shows the minimum flue discharge heights and positions for all wood burning and multi fuel applications.

In some cases, particularly when chimneys are towards the bottom of a sloping roof or at the eaves, it may be necessary to increase the chimney height above these minimum mandatory requirements. The reason for this is to clear pressure zones created by wind hitting the roof and nearby structures, like trees, which may interfere with the up draught required by the appliance or fire.

The maximum freestanding stack height above the roof for a traditional masonry chimney is 4.5 times the narrowest horizontal part of the chimney.
In the case of stainless steel system chimneys, the manufacturer’s installation instructions should be consulted; however in most cases it will be around 3 metres. This measurement is taken from the last point where the chimney stack passes the through or past the edge of the roof up to the chimney capping or termination. Tall chimneys may need bracing, always consult the manufacturer for advice.

For buildings with flammable roofs such as felted, thatched, or shingle roofs the flue or chimney the regulations are different. The flue or chimney must terminate at a minimum1800mm above the combustible surface.
5Which base support unit do you need?

You need a base support unit to that carries the weight of the outside flue. (A wall support only gives sidewards stability)

You can choose between:

- Base Support Bracket : Can carry the weight of maximum 5 m of flue

- Base Support: Can carry the weight of up to 12m of flue

Which base support unit do you need?
Base Support Bracket (carries up to 5m of flue) +£0.00 Base Support (carries up to 12m of flue) +£0.00
6Which wall support; and how many

Type of Wall support

Normally the wall brackets with a distance wall - flue with a 50 - 70mm are used.
You can take a higher distance (up to 150mm) if you want to pass along an overhanging roof, without using an offset.

Number of Wall supports

This depends on how many meters the flue goes along the wall.
We recommend to use a wall support every 3 meter along the wall. So every 2 - 3 meter above the Base support; 1 wall support.

Determine what wall support is needed
50 - 75mm, up to 3m along the wall +£0.00 50 - 75mm; 3 - 6m along the wall +£0.00 50 - 75mm; 6 - 9m along the wall. +£0.00 50 - 150mm; up to 3m along the wall +£0.00 50 - 150mm; 3 - 6m along the wall +£0.00 50 - 150mm; 6 - 9m along the wall +£0.00 150 - 250mm; up to 3m along the wall +£0.00 150 - 250mm; 3 - 6m along the wall +£0.00 150 - 250mm; 6 - 9m along the wall +£0.00 250 - 350mm; up to 3m along the wall +£0.00 250 - 350mm; 3 - 6m along the wall +£0.00 250 - 350mm; 6 - 9m along the wall +£0.00
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 +£0.00 All Weather Cowl +£0.00
8Do you need to support a free standing length of more than 1.5m?

You need to support the flue over the roof if the free end becomes higher than 1.5m.

We recommend to use a Roof Stabiliser Bracket, if the free end is between 1,5m and 3m.

The bracket comes with two telescopic legs that extend from 1m-2m in length. Also a band which secures around the flue and connects to the legs.

Do you need to support a free standing length of more than 1.5m?
No support needed +£0.00 For a freestanding flue of 1.5 - 3m +£0.00

Reset Wizard

Flue kits are based on general assumptions of the typical dimensions of houses and bungalows. You may need to add or take out certain items which can be done in the shopping cart. Other items can also be added to cart as necessary in the general Twin wall flue section. Flue-pipes.com does not take responsibility for the items installed in your flue system as this is merely a guide. Please check the twin wall flue pack is appropriate for your requirements. Refer to HETAS regulations, and building regulations for further clarification.

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Twin Wall Flue - External - Black-straight

1Diameter of flue liner:

What diameter of flue liner do you need?

2Choose the adapter between stove and twin wall flue

What kind of adapter between your stove and the twin wall flue?

3Horizontal distance stove - outside flue

What should be the horizontal distance between the heart of the stove, and the flue outside?

4Flue height outside

How many meters straight length (X) do you need?

5Which base support unit do you need?

Which base support unit do you need?

6Which wall support; and how many

Determine what wall support is needed

7What kind of Cap is required?

What kind of Cap is required?

8Do you need to support a free standing length of more than 1.5m?

Do you need to support a free standing length of more than 1.5m?

Your Selections

Your Selections

What other people are saying about us:

About us

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Flue pipes

Pitch of the roof	Height on the roof.
25°	1070mm
30°	1330mm
35°	1610mm
40°	1930mm
45°	2300mm
50°	2740mm

Twin Wall Flue - External - Black-straight

1Diameter of flue liner:

What diameter of flue liner do you need?

2Choose the adapter between stove and twin wall flue

What kind of adapter between your stove and the twin wall flue?

3Horizontal distance stove - outside flue

What should be the horizontal distance between the heart of the stove, and the flue outside?

4Flue height outside

How many meters straight length (X) do you need?

Chimney Heights and Termination

Simple rules

All the rules

5Which base support unit do you need?

Which base support unit do you need?

6Which wall support; and how many

Determine what wall support is needed

7What kind of Cap is required?

What kind of Cap is required?

8Do you need to support a free standing length of more than 1.5m?

Do you need to support a free standing length of more than 1.5m?

Your Selections

Your Selections

What other people are saying about us:

About us

Our services

Flue pipes