When installing a twin wall system you will nearly always want to start from the bottom and from here work your way up, as the straightest way is the most efficient way for a chimney system.
It is important to always calculate the chimney system before you start, this can be done your self or we can do this for you using our twin wall calculation software. Often the most efficient route if the stove is against an external wall is to go out through the wall and straight up and around the soffits.
Fitting a Twin Wall Rigid Chimney system going out through the wall
As stated already when planning and installing a twin wall system we start from the bottom and go up.
So the first step is to Lay the hearth, as discussed this can be a 12mm hearth as long as you are using a Stove that is 12mm hearth compatible.
Next, we position the stove so as to ensure it is the correct distances away from combustibles and that it has a minimum 225mm in front of the stove for spillage we recommend 300mm where possible.
From here we can work out exactly where we want the stove to go through the wall by building up the first few components such as the stove to twin wall starter piece, the first length and then the elbow. From here you can see the line that the pipe will need to take to exit the wall at a 45-degree angle.
Remove the starter components and position the wall sleeve over your marks, draw around the wall sleeve , cover up the stove or remove fully and drill holes around the wall sleeve at a 45-degree angle , this will give you the perfect hole if you’re not sure on your angles then you can always ask someone to hold the wall sleeve next to where you are drilling to help you. You will need a powerful drill with a long drill bit to keep the angle going through the two skins of brickwork and the cavity,
I find that it is worth going out in one or two places fully such as the top and the bottom and then remarking from the outside and doing the hole from there, this way you won’t chip off too much brickwork, we use a décor ring on both sides to hide the imperfections but they only give you a few inches for mistakes.
Once the hole is made, check that the wall sleeve will fit and then put the stove back and build the twin wall system up and out through the hole,
be sure to check that everything is level before you start adding brackets to the outside wall, the bottom bracket taking most of the weight needs to be a table bracket.
From here you can build up your twin wall system quite easily by putting brackets up as you go, you might need 2 more 45-degree bends and different length brackets if you are going around the soffits.
Be careful when attaching to the facias as they can we weak if there is nothing behind them, you might find that you need to use a bracing bracket from the roof if the height is over 2m unsupported depending on your system specifications.
Once the twin wall chimney is up and well suported you can fill in the hole using bits of brick and waterproof mortar to whether it in, it is also worth using a decor plate to cover up the hole and this also helps with water penetration if sealed up well with clear heatproof adhesive.
Fitting a Twin wall Rigid Chimney system going straight up through the house
Going straight up through the house if it’s on the bottom floor can be quite a bit more work. You might have two floors to go through and also a roof if it’s a 2 story house but then again it might just be a single roof if it’s a kitchen extension or a conservatory.
Going through a ceiling you will need to be aware of where the joists are as you will want to avoid these if possible. It might be necessary to cut and support a joist but it’s not something you should attempt unless you know what you are doing.
When going through a roof or ceiling you will need a vent fire support as well as ceiling and rafter supports.
Coming through the roof again is a very precise activity, you most certainly don’t want a leak or worse a fire in the loft.
It’s worth bearing in mind that when you pass through a level you will often need to re-route your pipe to go through the next set of rafters. To do this two 45degree bends will come in handy.
You will need a rafter support to secure the pipe while going through the roof. Where possible its best to find the area that you need to go through from the inside and then with the help of a screwdriver pushed though the felt go around onto the roof and remove the tiles.
Once you have the area cleared you can add the flashing over the pipe If you use a flexible flashing and storm collar then you will find that the roof angle doesn’t need to be an exact match whereas a lead flashing has a lot less room for movement. A flexible flashing also will give a tighter seal.
Seal with heat prof silicone and cut and replace the tiles.