A chimney runs up through the middle of the attic you are about to convert. Where yours lands decides how much it is in your way: at or near the ridge is the worst case, because the ridge is the only part of the roof with head height in it. Somebody is going to ask you what you want done with it, and the answer has to be given before the work starts.
Read this before anything else you have been told about chimneys
No chimney shall be removed where it forms part of a joint chimney stack with a separate dwelling house. That sentence is condition 1 of CLASS 2A, the class that made the removal of a chimney from a house exempted development on 27 July 2026. Where the stack is shared with next door, the new class is not available at all. So whether your stack is joint is the first question to settle, not a footnote — and it is a fact about your own house, which you can check without knowing anything about the rest of the stock. We are not going to tell you how many Dublin houses are in that position, because we have no survey of the stock we would stand over. Anyone telling you that chimney removal is exempt now, full stop, has read the class and not the column beside it.
This page is about a decision with three answers. Box it in and live with it. Take the breast out of the attic and leave the rest. Or take the whole chimney away. They cost different amounts, they touch different parts of your house, and — the part nobody writes down — only some of them are open to you, depending on facts about your house that you can establish before you ring anyone.
We are not putting a number on this one
There is no Irish cost benchmark for chimney removal that we are willing to stand over, and a contractor's own page quoting a price is evidence of what is being claimed, not a source. So we are not going to invent a range. What we can do is tell you what drives the price, which is more use when you are reading a quote: how many storeys the work passes through, whether scaffolding is needed to take the stack down and make the roof good, whether a structural design and an engineer's involvement are required, and how many rooms below end up being opened up and re-plastered. A quote that moves between the three options should move for those reasons, and you can ask which of them it is.
Box it in, take the breast out, or take the whole thing
These are not three sizes of the same job. They touch different parts of the house, and that is what separates them.
1. Box it in
The masonry stays exactly where it is, top to bottom, and the part of it standing in your new room is clad and finished so it reads as a pier rather than a lump of brickwork. Nothing outside changes, nothing on the floors below changes, and no load path is altered. You pay for it in floor area and in the shape of the room, and in whatever the breast does to where the bed, the stairs or the ensuite can go.
2. Take the breast out of the attic only
The breast is removed between the new attic floor and the roof, the masonry on the storeys below stays, and the stack above the roof stays. This is the option people assume is the cheap middle ground, and the reason it may not be is structural rather than cosmetic. What you have taken away was holding up what is above it, so the stack over the roof now has to be carried by something else, and that something else is a designed connection rather than a decision for whoever is on site that day. See what has to hold the rest of it up.
3. Take the whole chimney away
The stack above the roof, the breast in the attic, and the breast on each storey below, down to whatever level you choose to stop at. This is the option with the most reach: the roof has to be closed up and made good, every room the breast passes through is opened and re-finished, and any fireplace or appliance that used one of those flues stops existing. It is also the only one of the three that removes the problem rather than moving it.
Only the third of those changes what the street can see. Boxing in alters nothing outside, and taking the breast out of the attic leaves the stack standing over the roof exactly as it was. That distinction runs through the whole of the planning answer, and we come back to it below.
What changed on 27 July 2026
A new class was inserted into the exempted development regulations, and as far as we can find, no Irish page aimed at homeowners has said so. It is CLASS 2A, it sits in Part 1 of Schedule 2 to the Planning and Development Regulations 2001 under the heading Development within the curtilage of a house, immediately after Class 2, and it was put there by the Planning and Development (Exempted Development (Act of 2000)) (No. 6) Regulations 2026.
Here is the whole of it, column 1 and column 2:
Class 2A
The removal of a chimney from a house.
1. No chimney shall be removed where it forms part of a joint chimney stack with a separate dwelling house.
2. Roof finishes shall be the same as the existing roof.
3. This exemption is subject to compliance with Section 22 (protection of nests of wild birds) and Section 23 (breeding or resting places of protected wild animals including bats) of the Wildlife Act 1976, as amended.
CLASS 2A
Part 1 of Schedule 2, Planning and Development Regulations 2001, inserted by S.I. No. 343 of 2026
27 July 2026
The day it came into operation, per the commencement provision of S.I. No. 343 of 2026
3
Conditions in column 2. Article 6(1) requires the development to comply with all of them
Joint stack
Condition 1, and the one that rules the class out wherever the stack is shared with next door
The mechanism matters as much as the text, because it is what stops "there is a class for it" from meaning "you can do it". Article 6(1) of the 2001 Regulations reads:
"Subject to article 9, development of a class specified in column 1 of Part 1 of Schedule 2 shall be exempted development for the purposes of the Act, provided that such development complies with the conditions and limitations specified in column 2 of the said Part 1 opposite the mention of that class in the said column 1."
So the class is a conditional permission, not a general one. Fail any condition in column 2 and the development is simply not of that class — there is no partial credit, and no version of the job that is "mostly exempt". And the whole thing is subject to article 9, which takes it away again in the circumstances we set out further down.
Source: Planning and Development (Exempted Development (Act of 2000)) (No. 6) Regulations 2026, S.I. No. 343 of 2026, made 16 July 2026. Read the instrument - read 25 September 2026. Article 6(1) is from the Planning and Development Regulations 2001, S.I. No. 600 of 2001.
The joint stack condition, and how to tell whether it is yours
Condition 1 is not a caution or a design preference. It is the boundary of the class, and it is written as an absolute: no chimney shall be removed where it forms part of a joint chimney stack with a separate dwelling house.
What the condition describes is a particular construction arrangement, and it is worth being able to picture it. The stack sits on the party wall, one structure serving two houses, with your flues rising on your side of it and your neighbour's on theirs. That is a joint chimney stack. It is one thing, not two things that happen to touch, and the class does not let you take away your share of it.
Start outside and look at where the stack sits relative to the line between the two houses. A stack straddling the party wall, with pots grouped on both sides of that line, is serving both houses. A stack standing on your own gable or well inside your own roof plane, with the neighbour having a separate one of their own, is not. A terrace built with one stack per party wall, shared between each pair of houses along the row rather than one stack per house, shows this from the ground: count the stacks against the front doors and there are fewer of the first than the second.
Inside, the breast tells you which wall it belongs to. A breast built into the party wall — the wall you share — is the one to worry about. A breast on an external gable, or on an internal wall in the middle of your own plan, is far more likely to be yours alone.
What a joint stack does not do
It does not mean the chimney can never come out. It means CLASS 2A does not cover it, so the route is an application for planning permission rather than an exemption — and, separately, that a structure shared with somebody else's house brings their house into the structural question. Those are two different problems arriving together, which is why a shared stack is the point at which boxing in can stop being the resigned answer and become the sensible one.
The breast inside is a different question from the stack outside
These are two separate claims and they rest on two separate pieces of law. Merging them is how a homeowner ends up having done something they were not entitled to do while believing the opposite.
Inside: section 4(1)(h) of the Act
Section 4(1)(h) of the Planning and Development Act 2000 makes exempted development of "the carrying out of works for the maintenance, improvement or other alteration of any structure, being works which affect only the interior of the structure or which do not materially affect the external appearance of the structure so as to render the appearance inconsistent with the character of the structure or of neighbouring structures". Taking a breast out inside the house, with the stack above the roof and the roof itself left alone, is work that affects only the interior. This is the same provision our planning permission guide leans on for a rear rooflight, and the chimney is another branch of it.
Outside: CLASS 2A
The moment the stack above the roof comes down, the external appearance changes and section 4(1)(h) stops carrying the job. CLASS 2A is what covers that part, with its three conditions, and condition 2 — "roof finishes shall be the same as the existing roof" — is a live requirement rather than a formality. The hole the stack leaves has to be closed with the same finish as the roof it is part of, and a patch in a different material is a failure of the condition and therefore of the class.
The practical consequence is worth stating flatly, because it is the commonest way this goes wrong. If you have a joint stack, the internal half of the job is still capable of being exempted development under section 4(1)(h), and the external half is not available to you at all. A builder who takes the stack down as well, on the strength of "chimney removal is exempt now", has carried out development that needed permission — and the fact that the internal part was fine does not retrospectively cover the part the street can see.
Source: Planning and Development Act 2000, section 4(1)(h), as in the Law Reform Commission's revised text. Read the revised Act - read 25 September 2026.
The restrictions that take the exemption away again
Article 6(1) makes every class in Part 1 of Schedule 2 subject to article 9, and article 9 is a list of circumstances in which development that would otherwise be exempt is not. It is a long list. Two entries on it are the ones that bite on a chimney, and both of them are about the kind of street the house is on rather than anything about the chimney itself.
Development to which article 6 relates is not exempted development if it would, "further to the provisions of section 82 of the Act, consist of or comprise the carrying out of works to the exterior of a structure, where the structure concerned is located within an architectural conservation area ... and the development would materially affect the character of the area".
Note what that does and does not catch. It is about works to the exterior, so it bites on taking the stack down and not on taking the breast out of your attic. And it is qualified by "would materially affect the character of the area", which is a judgement rather than a measurement — which is precisely why it is worth asking the authority rather than deciding for yourself. Architectural Conservation Areas are designated in each local authority's development plan and are a matter of public record, so whether your address is inside one is checkable rather than arguable — and a uniform run of chimney stacks along a terrace is exactly the kind of thing an ACA designation is capable of being about.
Source: Article 9(1)(a)(xii) of the Planning and Development Regulations 2001 (S.I. No. 600 of 2001) and section 57 of the Planning and Development Act 2000 (revised text) - both read 25 September 2026.
What it does to the rooms underneath
A chimney is not a column of brick. It is a set of flues, and each flue exists to serve something. Take the chimney away and whatever was using those flues stops being usable, on every storey, permanently. That is obvious once stated and routinely not stated at all.
The requirement it engages is Part J of the Second Schedule to the Building Regulations — Heat producing appliances. The part that bites is J2(a):
"A heat producing appliance shall have adequate provision for the discharge of the products of combustion to the outside air."
Part J reaches your job through article 12 of the Building Regulations 1997, which applies the Regulations to all works in connection with the provision — by way of new work or by way of replacement — of services, fittings and equipment in respect of which Parts G, H or J impose a requirement. Our planning permission guide sets out that machinery in full, including why being exempt from planning has nothing whatever to do with whether the Building Regulations apply.
There is a second clause that matters more here, and it is the one people miss because it is about what you are allowed to break rather than what you are required to build. Article 9(2) of the Building Regulations 1997:
"No works shall be carried out to a building which would cause a new or greater contravention in the building of any provision of these Regulations."
Put those together and the rule for the room below writes itself. If there is a working appliance downstairs — an open fire, a stove, a back boiler, a gas fire — that discharges through a flue in this chimney, removing that flue leaves an appliance with no provision for the discharge of the products of combustion. That is a new contravention of J2(a) caused by your works, which is what article 9(2) prohibits. The chimney and the appliance go together: either both stay, or both go, or the appliance gets a compliant discharge by some other designed route. "We will just cap it off and they can stop using the fire" is not a plan, it is a thing somebody will be living with.
TGD J 2014 has a clause for this, and it is paragraph 1.6.1: "Where a decorative treatment, such as a fireplace surround, masonry cladding or dry lining is provided around a fireplace opening, any gaps that could allow flue gases to escape from the fireplace opening into the void behind the decorative treatment, should be sealed to prevent such leakage. The method of sealing and the sealing material used should be capable of maintaining the seal despite any relative movement between the decorative treatment and the fireplace recess."
That is the clause to name if a breast is being boxed in on a floor where the fireplace opening stays behind the new lining.
Source: Part J of the Second Schedule to the Building Regulations and Technical Guidance Document J - Heat Producing Appliances (2014), the current edition published on gov.ie. Read the document. Articles 9(2) and 12 are from the Building Regulations 1997 (S.I. No. 497 of 1997) - both read 25 September 2026.
What holds the rest of it up, and who signs for that
Removing part of a chimney is structural work. That is not a characterisation, it is how the Regulations define the job. Article 11(2) of the Building Regulations 1997:
"For the purposes of this article, 'material alteration' means an alteration (other than a repair or renewal) where the work, or any part of the work, carried out by itself would be subject to a requirement of Part A or B of the Second Schedule."
Taking masonry out of a load-bearing element is work subject to Part A (Structure). So the job is a material alteration by definition, not because of how large it is, and article 11(1)(a) then applies the Regulations to all works in connection with it. Article 11(1)(b) adds the rest of the house: the Regulations apply to every part of a building affected by those works, to the extent of prohibiting anything that would cause a new or greater contravention there.
The Part A requirement itself is A1, and one half of it is worth quoting in a guide about a stack you may be sharing with somebody else:
"A building shall be designed and constructed, with due regard to the theory and practice of structural engineering, so as to ensure that the combined actions that are liable to act on it are sustained and transmitted to the ground - (a) safely, and (b) without causing such deflection or deformation of any part of the building, or such movement of the ground, as will impair the stability of any part of another building."
Another building. On a semi-detached or terraced house, with a breast built into the party wall and a stack that may be serving next door as well, A1(1)(b) is not an abstraction. It is the clause that says the consequences for your neighbour's house are part of your design problem.
Whatever is left standing after the removal, what is now carrying it, and who designed that? If part of the breast goes and part stays, something has to support the part that stays. If the whole breast goes but the stack above the roof remains, something has to carry the stack. Both of those are designed elements. A builder who answers "we always do it the same way" is describing a habit, not a design, and the distinction shows up at sale time rather than on site.
Source: Articles 11(1) and 11(2) of the Building Regulations 1997 (S.I. No. 497 of 1997), and requirement A1 as set out in Technical Guidance Document A - Structure (2012), the current edition on gov.ie (read the document) - both read 25 September 2026.
The case for leaving it exactly where it is
Everything above is about removal, and removal is not the default answer. A joint stack rules the exemption out on its own; section 57 closes it for a protected structure; and in an ACA, article 9(1)(a)(xii) turns it on whether the works would materially affect the character of the area. Boxing in is the option that touches nothing, and it deserves to be argued for rather than treated as the thing you settle for.
What it costs you is floor area and room shape, and those are measurable before you decide anything. Go up with a tape and take three numbers:
How far the breast projects from the wall it is built into, and how wide it is. That rectangle, plus the thickness of whatever cladding goes round it, is the floor area you are giving up.
Where it stands relative to the ridge. This is the one that matters most and the one people forget. Floor area under the slope, where you cannot stand anyway, is cheap to lose. Floor area along the ridge line is the only full-height space you have, and a breast sitting in it takes the most valuable part of the room. Two houses can lose the identical number of square metres and have completely different outcomes.
Then draw the room you actually want — bed, wardrobe, the head of the stairs, the ensuite if there is one — with the breast in place. If it all still works, you have your answer and it is the cheap one.
The decision, in the order it has to be made
Four questions, and they have to be asked in this order, because each one can close off options that the next would otherwise open.
If yes, CLASS 2A is out. Taking the stack down is not exempted development for your house, whatever anyone has read about the 27 July 2026 change. Your options narrow to boxing in, taking the breast out inside only under section 4(1)(h), or applying for permission. If you cannot tell, the section 5 declaration is how you find out on the record.
Three outcomes, and by this point you should know which is yours.
Box it in
The stack is joint, or the house is protected or in an ACA, or there is a fire still in use downstairs, or the breast lands somewhere the room can absorb. Nothing structural changes, nothing external changes, and the work is cladding and finishing. Ask for the fireplace opening to be sealed per TGD J 2014 paragraph 1.6.1 where one is being covered, and ask in writing what is being done with the flues.
Take the breast out in the attic, leave the rest
You need the floor area, nothing below is burning, and either the stack is joint or you would rather not touch the roof. Internal works under section 4(1)(h), and a material alteration under article 11 of the Building Regulations 1997 with a Part A design behind it. The question that decides whether this is the cheap option or the expensive one is what now carries the stack above, and you should have that answer before you have a price.
Take the whole chimney away
The stack is yours alone, the house is not protected and not in an ACA, and nothing below still uses a flue. CLASS 2A covers it as exempted development provided all three conditions are met, including making the roof good in the same finish. It is the most invasive of the three and the only one that ends the matter. Every storey the breast passes through is in scope, and so is the certification.
One thing we are not going to claim
We cannot tell you whether your stack is joint, and nobody can from a web page. What this page can do is tell you that it is the first question, that CLASS 2A of Part 1 of Schedule 2 is where the answer lives, that section 4(1)(h) and CLASS 2A cover different halves of the job, and that section 5 of the Act is how you get a planning authority to say so in writing. Take those four things to whoever is pricing the conversion and you will have a better conversation than the one that starts with "can we get rid of the chimney?".
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