Loft conversion – what do I need to know? (not self build)

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  • Loft conversion – what do I need to know? (not self build)
  • clubber

    I can’t see your pic but my place is a 30s end of terrace with hip roof like you describe.

    Within regs you’re limited on size (40m2 IIRC though if you’re in a semi that’s 50m2 IIRC) so we added two dormers – one at the side (where the hip is) for the stairs and a bigger one at the back for the main bedroom/ensuite. It sounds like you’re going to have more space than us though.

    I can’t really comment on the options other than to say that ours has the foil backed foam insulation and it seems to work well.

    Premier Icon midlifecrashes

    Don’t know why a combi wouldn’t be OK for a 4 bed/2 bath house. Just buy one with the wattage you need, same as you would for any other system.

    Premier Icon ransos

    Our conversion starts soon – we’re having a hip to gable conversion on our 30s semi. There’s enough room for a double bedroom and en-suite without adding a dormer, which was important to us because I hate the look of them.

    We’re keeping the existing combi boiler – only thing to note is that it won’t be able to supply adequate flow for two showers at the same time. Not a big deal to us, but it might be to you.

    Make sure you go for top-hinged veluxes that can be pivoted round for cleaning.


    combi will be fine.

    if you put the wrong combi in yes itll give you gyp – most combi systems ive seen are well underspecced to keep costs down.

    my mate has one in his 4 bed , 2 bathroom about the size of a bedside cabinet – It really struggles to heat his place – and a bath is out of the question.

    i put in one the size of a washing machine with a much bigger capacity – suited to the house its in … 3 bed 2 bathroom.

    heats the house without issue and ill have no issues with a thermostatic mixer shower in the future if my parents experiances with a similar boiler are to go by.

    I have a 30’s semi too.

    What kind of prices are we talking for a gable/dorma loft?

    I’m in London so will no doubt be more but a ballpark would be good.



    £31K for mine in Bristol

    shower room fittings (eg shower, toilet, sink, tiles extra on top of that

    Docoration (eg painting) not included

    Existing combi boiler remained (and is just up to the job though the additional shower is electric so really it’s only a couple of small additional radiators.


    Thanks all so far.

    MM – I’m in Hertfordshire so prolly a bit cheaper than London, asked the second chappy for a ballpark and he said about £32k (undecorated) without the Megaflo system and £36k with it.


    I’m waiting for the quotes to come back for ours… hoping to start ibn June..

    First off, i’d get it drawn up by an architect first, don’t let a builder design it… OK, so it’ll add a bit to the total price, but a good set of proper construction drawings, which can be submitted to, and approved by Building Control are worth every penny.

    Be sure of what you want before you go out for quotes, and be even more sure before anyone starts work, variations are where builders make their money.

    Second, i’d recommend applying for a certificate of lawfulness from the council before you start, this confirms that the proposed works can be completed under permitted development, and don’t need planning permission.

    There is no reason you can’t use a combi boiler, provided it is sized properly. however if you want to be able to use two showers at once etc then megaflo might be the way forward.

    You can use what you like for insulation, provided it meets the building inspectors approval for U-value and fire proofing. Kingspan/similar is the easiest way to achieve this, and you’ll probably need 150mm of it in the roof of your Dorma.


    Oh, and if you haven’t already, go and talk to your neighbour about it. You’ll almost certainly be inserting Steels into the Party wall to support the floor, so will need them to sign a Party Wall Agreement, so the sooner they are on board the better.


    So tentatively decided into getting the loft converted (although having read the financial doom thread maybe a small holding and firearms would be a better investment.)

    Kinda like this – Flikr link

    We’re going to square off the slopey roof to form a gable(?) and build a boxy thing on the back (dormer)?

    We’ve had a couple of builders around and have a few more coming around and they are all (unsurpringly) recommending different things. Apparently the space is big enough to have two ok sized bedrooms and a bathroom up there, we were thinking one room and a shower room.

    As we may as well change our ageing CH system at the same time and because we have the cold water tank in the loft –

    1st chappy says to go for a combi boiler – remembering threads on here that this is not optimal for what would be a four bedroom two bathroom house?

    Second chappy says go for megaflo system (spendy)

    Insulation – first chappy had pictures of what looked like aluminium foil type insulation – never seen this before, second chappy said the more usual kingspan/celotex stuff.

    So a bit bemused by the options, any hints tips from the STW hive mind?


    We had exactly the same done. Paid 20,000 for hip to gable, roof and veluxes, rear dormer, steelwork and floor and stairs. Did the insulation, stud walls, plastering, electrics and decorating myself.
    Steel beams were able to run front to back so no party wall issues.
    Insulation was 50mm foiled celotex between rafters, overlaid with tlx silver multifoil, as per architect plans. Gable and dormer cheek walls were brick external, stud internal, with 100mm foiled celotex between studs. Paid about 800 for drawings and calcs, and 300 for building regs inspection. Kept existing combi. Make sure builder makes every effort to salvage every inch of headroom. A good builder will see opportunities that an architect may not have picked up on.


    Thanks all some good stuff here. Not sure I’ll need steels to hold up the floor, the joists (?) look massive and are fairly numerous. Another oddity is that first chappy said you can have mains smoke detectors in all rooms and/or fire doors, second chappy said fire doors and smoke detectors.

    Checking this Planning Portal seems second bloke is correct?


    We just had our done.

    Fi.d your own architect and spend time with him on site pondering your options and taking advice on what you can do with the space.

    Use local council building control at they are a bit anal, which is good for you, not the one recommended by the builder.

    On ours the loft conversion companies quotes came in far cheaper thoan the builders quotes.

    Make sure you negotiate all your extras onto the price before you sign the contract.

    Go and see a few of their previous conversions.

    Ensure that your team are on site from start to finish and not juggling multiple jobs.

    We put a gable end window in our bedrooms as well as a Velux, it makes it more room like, required planning permission, but no issue.

    Payment will be in installments, try and get the final payment to be as significant as you can as it will keep them focused on getting done and gone. We’ve still not paid the final couple of grand, and they started in Aug 2012.

    There are some well shonky firms and ideas of workmanship out there, as we found out the hard way.


    Bimbler – we have mains smoke/fire detectors on each floor in the landings (not each room) and fire doors on ALL habitable rooms (not just the new rooms) – basically all doors in the house other than the bathroom.

    Premier Icon DaveP

    We have a (now) 5 bed house. Ummed and arhh about combi/megaflow. went combi and dont have enough flow and there is no way 2 showers can work.
    That is my biggest regret. I am guessing that a megaflow would have helped, but the incoming flow might have limited it’s usefulness.

    We didn’t need steels and therefore didn’t need to hassle the neighbour (loft span is probably 10m x 4m).


    FWIW, we did need a steel but it fitted into the chimney breast so didn’t need to hassle the neighbour.


    We had to chicken wire and 100mm rockwool the floor joists because ceilings on first floor were not 30min fire rated.
    We also had to have mains (and linked) smoke detectors in all habitable rooms as the internal doors were not fire rated. With fire rated doors, I think we could have got away with detectors just in hall and landings.

    where in Hertfordshire are you??


    Smoke detectors – I think probably more effective to have smoke detectors in all habitable rooms than have fire doors which, let’s face it, will never be shut. Presumably mains smoke detectors have secondary power source because not exactly useful if your electrics are on fire

    Might get one of these too

    Reading up on Combi vs Megaflo, seems even the staunchest Combi backers say that they’re not up to 2x showers, so I suppose a combi and power shower would work?

    Anyway these are details at this stage I suppose.

    We’d need a steel to carry the extra roof out to the gable and this would have to go into the chimney as that is central, would this stop the chimney working – currently have a back boiler which vents through the chimney – or would there be some sort of extra duct in there already?

    andylaightscat – Hertford


    “Presumably mains smoke detectors have secondary power source because not exactly useful if your electrics are on fire”

    they have 9v batterys.

    mines are currently not connected as the dust and such in the hall sets them off – i put them in the kitchen while working now and put them back in the hall when im done and the dust has settled before bed.

    but believe me they work and are loud even when not attached to mains 😉

    dropped you a mail about loft

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