AdamD Posted October 9 Share Posted October 9 Currently have a 3 bed semi detached with two decent sized bedrooms and a box room converted to home office. Have a toddler and baby so need a solution to give them their own rooms and a loft conversion seems the way forward. To move to a bigger house in the area will be another £150k so is out of the question. We have a good loft space and could make it the biggest room plus en suite. Now, budget. No idea really how to forecast this as totally new to it but it would all need to be done by trades. All in company would be best as we want minimal hassle and want it done as quickly as possible, won’t be easy with a 2 year old and a 5 month old baby, but appreciate this will be far more expensive. What we want is a rear dorma and hip to gable at the side for maximum space and headroom. 35 sq metres roughly. We are on the south coast fyi. What sort of ball park budget should be realistic and what other considerations before proceeding? Link to comment Share on other sites More sharing options...
Redbeard Posted October 9 Share Posted October 9 No idea about the price but 'second-hand' experience tells me not to assume that not all 'loft conversion specialists' do a fantastic job. Issues range from failing to understand that the party walls of a terraced house attic (with a cold loft on either side) need insulating, not just dot-and-dab plasterboard, to dreadful detailing of insulation and air-tightness and a complete failure to calculate properly the eaves ventilation needed. 1 hour ago, AdamD said: what other considerations before proceeding? Well, if the FF ceiling joists are typical and the space above the joists is not as generous as you think once the 'joist uplift' and insulation 'downward thrust' are taken into account you may have to take the FF ceiling level *down*, which takes your FF out of use for the duration. Link to comment Share on other sites More sharing options...
AdamD Posted October 9 Author Share Posted October 9 Sorry, what is FF? Link to comment Share on other sites More sharing options...
Redbeard Posted October 9 Share Posted October 9 (edited) Sorry! First Floor. The joists immediately below the space you hope to use. Edited October 9 by Redbeard 1 Link to comment Share on other sites More sharing options...
AdamD Posted October 9 Author Share Posted October 9 Thanks. I’m a layman so not massively following, whilst I kind of understand what you’re saying. What is typical and how much space may be lost ? can you explain joist uplift and downward thrust in this context please ? Link to comment Share on other sites More sharing options...
ETC Posted October 9 Share Posted October 9 Is your house timber framed? Link to comment Share on other sites More sharing options...
Redbeard Posted October 9 Share Posted October 9 (edited) OK, let's say you currently have 75mm (quite typical) deep joists and your structural engineer says you need 175 or 200mm joists. Your new joists will either protrude above (reducing the height in the new bedroom) or below the joists (reducing the ceiling height in the room below) by 100-125mm. Let's assume that you have 75mm rafters too. The gov't's guidance suggests a 50mm ventilation gap above any insulation, so you can only get 25mm between the 75mm joists. If you use polyisocyanurate (PIR) insulation (Kingspan or Celotex) you'll need a further 125mm to get a compliant U value of 0.16W/m2K as required by the Building Regulations. Add to that the need for say 25mm battens and 15mm of plasterboard and skim, and the need to to have some ventilation 'crossover' at the top of the room (and of course the need for floorboards which I have not yet advised you to put on top of the joists(!) ) and you'll see how the height loss builds up. If, like many attic rooms, you want to have a flat area of ceiling at the top of the room you will of course reduce the room height still further. If we go for 2.1m as a desirable minimum height the example above (losses at top and bottom of the room) could mean that you lose up to 290-315mm off the apparently-available height. If you decide to use more 'friendly' insulants you'll lose more than that. If you have a good tall steep-pitched roof then you may be fine. Not tall and not steep-pitched, you may be less fine. Edited October 9 by Redbeard 1 Link to comment Share on other sites More sharing options...
AdamD Posted October 9 Author Share Posted October 9 1 hour ago, Redbeard said: OK, let's say you currently have 75mm (quite typical) deep joists and your structural engineer says you need 175 or 200mm joists. Your new joists will either protrude above (reducing the height in the new bedroom) or below the joists (reducing the ceiling height in the room below) by 100-125mm. Let's assume that you have 75mm rafters too. The gov't's guidance suggests a 50mm ventilation gap above any insulation, so you can only get 25mm between the 75mm joists. If you use polyisocyanurate (PIR) insulation (Kingspan or Celotex) you'll need a further 125mm to get a compliant U value of 0.16W/m2K as required by the Building Regulations. Add to that the need for say 25mm battens and 15mm of plasterboard and skim, and the need to to have some ventilation 'crossover' at the top of the room (and of course the need for floorboards which I have not yet advised you to put on top of the joists(!) ) and you'll see how the height loss builds up. If, like many attic rooms, you want to have a flat area of ceiling at the top of the room you will of course reduce the room height still further. If we go for 2.1m as a desirable minimum height the example above (losses at top and bottom of the room) could mean that you lose up to 290-315mm off the apparently-available height. If you decide to use more 'friendly' insulants you'll lose more than that. If you have a good tall steep-pitched roof then you may be fine. Not tall and not steep-pitched, you may be less fine. Really interesting and useful, thanks. I’ll challenge the builders with this when I speak to them about the quotes. not sure what is classes as tall and steep so I’ll get up there tomorrow and measure to, say, the highest point and post here for opinions! Link to comment Share on other sites More sharing options...
Redbeard Posted October 9 Share Posted October 9 I did not complete the sum! My dodgy maths above suggest that if you do not drop the joists into the room below you'd need at least 2200- 2300 height from the existing joists to wherever the ceiling would want to be. That would give you a very 'pointy' room with little or no flat ceiling, so it would 'feel' better if there was more flat ceiling, which of course means more overall height required. 1 Link to comment Share on other sites More sharing options...
Redbeard Posted October 9 Share Posted October 9 9 hours ago, AdamD said: what other considerations before proceeding? Check if this is Permitted Development or needs Planning Permission. You may already have done that. 1 Link to comment Share on other sites More sharing options...
joe90 Posted October 9 Share Posted October 9 You only need planning permission if installing a dormer in the front facing roof, dormers on the rear are permitted development (tho the council may tell you you need planning permit ion!!,!). Veluxs on the front do not need planning permission. You WILL need building regs whatever you do. I would suggest you get multiple quotes from loft conversion companies with personal recommendations not reviews which companies can write themselves. If companies cannot give you previous customers details to get your own feedback avoid them. 1 Link to comment Share on other sites More sharing options...
olley Posted October 9 Share Posted October 9 I got a quote for our dormer conversion this year. 7m x 10m bungalow with full length dormer. Quote was for 2 beds and 2 bathrooms ready for occupancy, £125,000. Just for a bare shell ready for me to insulate, second fixings, plumbing etc I was quoted over £60,000 1 Link to comment Share on other sites More sharing options...
Lofty718 Posted October 10 Share Posted October 10 3 hours ago, olley said: I got a quote for our dormer conversion this year. 7m x 10m bungalow with full length dormer. Quote was for 2 beds and 2 bathrooms ready for occupancy, £125,000. Just for a bare shell ready for me to insulate, second fixings, plumbing etc I was quoted over £60,000 Seems insane pricing A loft conversion like the OP's should cost around 60k in Greater London and the SE, not including flooring and bathroom fixtures Link to comment Share on other sites More sharing options...
olley Posted October 10 Share Posted October 10 The quote included £16,000 for scaffolding, they wanted a tin hat put over the bungalow. The prices do seem insane, but from the two bare shell quotes of £60,000 seemed to be the going rate. So far I have spent about £10,000, for architect, structural engineer, joists, steel ridge beams, RSJ,s 3 off and bits and bobs like screws. Now about to start on the dwarf walls. Link to comment Share on other sites More sharing options...
Gus Potter Posted October 11 Share Posted October 11 On 09/10/2024 at 12:37, AdamD said: Currently have a 3 bed semi detached with two decent sized bedrooms and a box room converted to home office. Hi Adam. Can you post a few photos as that would help a lot. In the attic.. so we can see how the roof is constructed, the external elevations all round and how the house sits in the garden, the garden size and where the boundaries are. Maybe you kept the selling agents floor plan when you bought the house? At the moment it's so open ended that its hard to make meaningful comment that might help you. You should have a title plan.. the deeds.. sanitize that so you can't be identified and post it. On 10/10/2024 at 19:15, olley said: So far I have spent about £10,000, for architect, structural engineer, joists, steel ridge beams, RSJ,s 3 off and bits and bobs like screws. Now about to start on the dwarf walls. That is a helpful comment. For attic conversions the design fees tend to be heafty. It may seem like a small job but some of the attic conversions I do require a huge amount of my Architectural, SE design and detailing time . I wear two hats.. I'm an SE primarily but also do the Architectural design side of things. In terms of Architectural and SE design fees these can amount to 15 -25% of the project value to get all the design work and detailing done and the LA / BC approvals. On a good day you may get this down to 10- 12% if what you are doing is simple. That said, a good experienced designer can save you a pile of cash. One week of labour for a good joiner (chippie) comes in at £1.0 to 1.2K a week! so please bear that in mind. Also a good design will have access to Contractors that they work with on a regular basis that they can trust not to rip you off. Now it may be that you want to go back and see if it is more economic to extend at ground floor level.. this gives you raw extra square footage that will also increase the value of the house.. often more than an attic conversion on a pro rata basis.. remember you often need a stair so you take a step back before you can go forward. 3 Link to comment Share on other sites More sharing options...
DevilDamo Posted October 12 Share Posted October 12 On 09/10/2024 at 22:37, joe90 said: You only need planning permission if installing a dormer in the front facing roof That isn’t the only trigger point. Link to comment Share on other sites More sharing options...
joe90 Posted October 12 Share Posted October 12 1 hour ago, DevilDamo said: That isn’t the only trigger point. What else would trigger planning? Link to comment Share on other sites More sharing options...
DevilDamo Posted October 12 Share Posted October 12 34 minutes ago, joe90 said: What else would trigger planning? No PD rights, being a corner plot, having a different external finish to the house are just a few examples. Link to comment Share on other sites More sharing options...
joe90 Posted October 12 Share Posted October 12 I respectfully disagree, I did a loft conversion on a corner plot house and built dormers on the two elevations not facing a highway and done under PD. Changing the external finish does require planning but not required to built a loft conversion. Link to comment Share on other sites More sharing options...
DevilDamo Posted October 12 Share Posted October 12 @joe90 Respectively, you implied the only reason you’d need Planning is if it related to a front dormer… which is not correct. Link to comment Share on other sites More sharing options...
joe90 Posted October 12 Share Posted October 12 35 minutes ago, DevilDamo said: No PD rights, being a corner plot, Interesting, this from the above listed guidance on permitted development rights. Page 7 ”There will be only one principle elevation to a house” I had been informed by planning on several loft conversions I had done that planning was required till I proved they were wrong on those occasions. Link to comment Share on other sites More sharing options...
DevilDamo Posted October 12 Share Posted October 12 @joe90 I am well aware of the PD rules. If the OP has a corner plot, they’d have to establish which is the principal elevation. So being a corner plot is an added restriction for homeowners to establish. Btw, my initial comment to you was stating that front dormers are not the only trigger point for needing Planning. That is unfortunately correct. Link to comment Share on other sites More sharing options...
joe90 Posted October 12 Share Posted October 12 (edited) 2 hours ago, DevilDamo said: I am well aware of the PD rules 13 hours ago, DevilDamo said: No PD rights, being a corner plot, I think this contradicts the planning portals information. https://ecab.planningportal.co.uk/uploads/miniguides/lofts/Lofts.pdf https://www.gov.uk/government/publications/permitted-development-rights-for-householders-technical- class B Edited October 12 by joe90 Link to comment Share on other sites More sharing options...
DevilDamo Posted October 13 Share Posted October 13 @joe90 No PD rights can trigger Planning. Being a corner plot can also trigger Planning as it would depend upon which elevation is deemed as the principal elevation. The principal elevation is not necessarily or always the front elevation, which your previous comment alluded to. I’m not sure why you’re trying to pick holes in everything and taking parts of it out of context 🙄 Link to comment Share on other sites More sharing options...
joe90 Posted October 13 Share Posted October 13 42 minutes ago, DevilDamo said: you’re trying to pick holes in everything and taking parts of it out of context 🙄 Rather than pick holes I am quoting planning rules that exist and those i have dealt with over years of actually doing loft conversions. I hereby back out of this thread. Sorry @AdamD. Link to comment Share on other sites More sharing options...
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