Loft conversion - Realistic expectations

[cloud91]

Hello,

 

I lived in a 3 bed end terraced property in the west midlands, built around the 1940s.

 

As I work from home, one bedroom is consumed by my office. We have one reception room and a small garden, so it isn't feasible for me to extend downstairs.

 

I am therefore considering a loft conversion. I have had my loft insulated between the rafters and then plasterboarded. We also boarded the floor to maximise storage space. prior to doing this, he reinforced also the beams with new beams adjoining to each of them, but I am not sure exactly what wood they were. But, I remember they spent around 1.5 days very loudly fastening the long bits of wood to the beams already there for more support. But. As he has boarded over the top, I don't know if it's adequate. So, unsure if this would need further reinforcing.

 

The wall to my neighbour is mostly flat, but angles towards the front of the house. The front wall of the house is entirely flat. The side of the house where the alleyway and rear of the property are both angled.

 

So, I was considering, if I got a long side dormer and a rear side dormer, like a L shape, then this in theory should maximise headspace and therefore, maximise the use of the loft. 

 

Our first story double bedrooms are 11*11, 9.5*12.5 and 7.5*9.5. we also have a small bathroom on the first floor measuring at 5.5*5.5. all dimensions in feet.

 

The overall loft space internally edge to edge is 16.5ft wide by 24.5ft deep.

 

I hope that's clear.

 

So, my questions are as follows:

Is an L shape dormer realistic based on my description?

Would I be able to yield a similar amount of space in the loft, or would it be reduced to 2 bedrooms and 1 bathroom?

Does the floor description sound adequate? I know it'll have to be lifted and checked. But, does it sound about right?

How long would a job like this take on average?

Costs fluctuate depending on builders and finishing touches, but what would be a realistic range for the cost of a loft conversion with an L shape dormer nowadays?

 

Thanks in advance. 

 

I'm no builder, so, if I have missed any important information, please let me know. 

 

I have attached pics to help.

 

[Redbeard]

Welcome!

 

Judging by how much of the purlins (horizontal beams) I can see it looks like no extra depth has been added at ceiling level. Therefore if we assume the rafters are 75mm (they might be 100, but unlikely more) then, if a ventilation gap of at least 25mm (50 is better) has been left between the back of the tiles and the insulation, you will have 50mm of insulation at best, if PIR (polyisocyanurate - Kingspan or Celotex-type insulation) has been used. If no vent gap has been left you may get moisture issues (wet roof timbers) and if you wanted to comply with Building Regs (which for a loft conversion you have to) you would need 150mm of PIR, not 50.

 

As regards the additional timbers you had fitted, everything depends on whether they were specified by a structural engineer, and whether they span from brick wall to brick wall (as additional supports) or are simply fixed to the sides of the existing joists. If the latter then they may have added minimal extra strength, but added extra weight for the original joists to carry. I am not a structural engineer, but you need one, and no doubt one will be along soon.

 

As to the dormers, probably no problem in principle, but I am not sure whether they would be Permitted Development (i.e. you don't have to make a Planning Permission application) or not. I've no time just now, but search 'dormer windows - Planning Permission/Permitted Development and you will find guidance.

 

Most of all: Will you still have room to stand up when (maybe) the floor has come up in height and the ceilings have come down in height?

[cloud91]

Hi,

 

Thanks for the response.

 

I'm unsure about the insulation gap, but I will consult with the guy who did the work. 

 

Also, I think he just fastened the timbers to the existing beams. But, I'm not 100% sure.

 

I didn't measure the height. But, the highest point is very high, I don't think I could touch it if I stretched my arms. Would a dormer be equitable to the same height as the highest point of the loft? 

Edited Friday at 12:24 by cloud91

[Redbeard]

1 hour ago, cloud91 said:

I didn't measure the height. But, the highest point is very high, I don't think I could touch it if I stretched my arms. Would a dormer be equitable to the same height as the highest point of the loft? 

 

Almost certainly not. It depends to come extent on the insulation strategy for the dormer, and how far down the existing roof you have to come to get a good structural 'connection' between the dormer roof timbers and the existing roof. You need the existing ridge to 'work' with the dormers, so the likelihood is that you'll have a small bit of pitched roof below the ridge tiles (let's say an absolute minimum of 300mm), then the roofing felt/membrane (I am 'building' the dormer 'backwards', from the top!), then - if you choose a 'warm roof' with the insulation above the deck - 150-250mm of rigid insulation, then say 175mm rafters plus 15mm skimmed plasterboard, then the internal ceiling below the apex could be as much as 625 - 725mm below the very top of the ridge tile. That is like taking your 'outstretched arm' out of the equation, so if your fingers would reach 150 or 300 from the top of the space, now that would be the top of your head 150-300 (total guesswork figs) from the top.

 

If you do a 'cold' roof, with all its possible attendant condensation issues, you could perhaps lose 100-150 of that 625-725.

[Redbeard]

2 hours ago, cloud91 said:

Does the floor description sound adequate? *No, unless it was done to a structural engineer's spec in accordance with plans for a conversion - which you weren't planning at the time, I think.*

 

I know it'll have to be lifted and checked. But, does it sound about right?

 

*No, as above*

 

How long would a job like this take on average?

 

* Obviously depends how much labour you can throw at it and whether each trade can follow the last with no gaps, but I'd say 2 months would seem really fast and 4 would not be unexpected. I am sure there will be some who have managed quicker even than 2 months, but start factoring in delays between trades and time expands.

 

* Costs fluctuate depending on builders and finishing touches, but what would be a realistic range for the cost of a loft conversion with an L shape dormer nowadays? Not a clue nowadays but I have anecdotal evidence of a couple of loft conversions with a lot less dormer than you propose. One was done by a general builder and the detailing as not very good, and one was done by a 'loft conversion specialist' and it only ended up 'all right-ish' due to the tenacity of the client. Both, if I remember correctly, were in the £35 - 40,000 bracket and the most recent one was 6 years ago.

 

 

To make this more bullet-pointy see interjections* above:

 

I will be delighted if others come back and say 'No. You could do it far cheaper than that' but really until you have 'laid it bare' and got plans done you cannot get an accurate price.

 

Edit: Forgot re stair. To get a stair in you are likely to lose something off a 1st floor room, unless your landing is very 'generous', and because of the sloped ceilings and the need for a min 1.8m (IIRC) headroom your stair will 'chop up' the space somewhat. Basically, as far as I can see, it is going to have to come up under the ridge (in the middle of the space).

 

 

Edited Friday at 14:04 by Redbeard
Added stair