converting inset woodburner to open inset fireplace

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Hi,

As part of our renovation project we've removed an inset solid fuel stove (with backboiler) with the intention of replacing it with a traditional victorian style open fire with cast iron surround. Largely for aesthetic purposes, but also want it to function on the odd occasion I have pyromaniac urges, it'll be used for solid fuel, most likely wood.

The chimney structure is effectively freestanding in the centre of the house (it ties into one thin internal wall) made from engineering brick (hard as nails) and is quite massive. on the ground floor it consists of a pair of 'cavities' side by side, one facing the front of the house for the front room, one facing the rear for the back room. The rear fireplace is unused, and closed up with a small vent at the bottom.

On removing the old stove we discovered that the existing structure had been butchered somewhat to allow fitting of the stove:

  • The brickwork supporting the right hand side of the lintel had been removed, leaving the lintel held up by mortar to the surrounding brickwork only.

    The dividing structure between the front room and back room fireplaces had been removed, effectively making a single cavity with 2 flues.

    The external side of the cavity adjacent to the unused fireplace had been opened up (badly) to allow pipework access to the old back boiler.

The sketch plan below illustrates this a bit:


The red hatching is removed structure that has now been repaired/replaced. The front room, where i intend to put the fireplace is to the left of the structure in this view.

Other electrical work in the room has required the affected chimney breast to be batten & boarded to allow electrical services to be flushed onto the face - this is shown in blue on the sketch.

We've got a cast iron fireplace, hearth, and fireback/chairbrick from B&Q and I've been reading around a few forums websited trying to figure out what else I need to make it all work.

The fireplace is a bit like this:

tregaron-hilight.jpg


(the style is different, but the construction and format is the same)

Chairbrick:

chairbrick-for-cast-iron-firebacks-533-p.jpg


The floor is concrete, so don't think I'm going to have any trouble with the hearth side of things.

Flue liner - there isn't one at the moment, I guess I need to install one, along with a new chimney pot on the roof. Part J (sec 2.6) of the building regs says 200mm dia for upto 50kW - I guess this would cover my scenario, though I've no idea of the kW rating of an open fireplace. Any suggestions on installing a flue-liner - it's not a job I'm looking forward to (climbing around on the roof isn't my idea of fun) and I am considering getting someone in for that aspect at least - who/what should I be looking for in a flue-liner fitter? Any approvals, certification bodies, etc?

Ventilation - There's a single airbrick at the front of the house (almost exactly opposite to the fireplace) that I suspect was to serve the original stove/backboiler I suspect this will need to be enlarged or added to to meet thet 50% area of the flue mentined in the building regs.

I can't find much information on fixing and securing the fireback to the buildign structure (I assume it needs to be adequately fixed) , and how it should interface with the flue-liner - I'm guessing some sort of adaptor plate is needed to go from the throat of the chairbrick to the liner - where would I get one of these from?

As the front face of the chimney breast has been brought forward by the plasterboard, I'm unsure as to any extra treatment required for the board close to the fire opening - how far back should I cut the board away from the opening? The opening itself is quite smallish - 500mm wide by 800mm high.. whilst the iron fire-surround is more like 1000w x 1200h.

I'm also guessing that ideally the chairbrick should be fitted so its front is flush with the wall before the iron surround is fitted - I'm concerned this might constrict the throat too much due to the thickness of the lintel and the fact the wall is now deeper. If the chairbrick needs to maintain a minimum throat and be set back how should I fill the gap between it and the cast iron surround? Cement? some sort of fire-board?

Sorry for the long post, is there anything else I might not have considered?
 
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Flue liner - there isn't one at the moment, I guess I need to install one, along with a new chimney pot on the roof. Part J (sec 2.6) of the building regs says 200mm dia for upto 50kW - I guess this would cover my scenario, though I've no idea of the kW rating of an open fireplace. Any suggestions on installing a flue-liner - it's not a job I'm looking forward to (climbing around on the roof isn't my idea of fun) and I am considering getting someone in for that aspect at least - who/what should I be looking for in a flue-liner fitter? Any approvals, certification bodies, etc?

The flue would need to be 200mm (8")

Get yourself a HETAS engineer to install the flue,plenty on the HETAS website for all over the country.

Normally a "Gather Unit" is used to fit the liner into the chimney at the bottom.These are normally fixed into the chimney by cementing them into place.The liner is fitted into the adaptor on the top.The grade of liner is dependant on what you are burning.A grade of 316/316 is suitable for most fuels,if you want to go the extra mile 904/904 should cover everything but it is expensive.

Gatherunit.jpg


Fixing at the top is your choice but normally a plate and clamp to hold the liner and then put the pot back on.
 

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