How do you workout a loft conversion finish height ?

Legacy_user

UK - Semi-detached 1906 property.

Hi, We have had Full Plans Application submitted by architect and passed by local authority. Dormer ensuite Pre war semi detached. Never been underfelted so is being reroofed too. It has load bearing walls including a central wall running parallel under the apex ridge beam.

Height= 235cm from under the ridge beam to the top of the floor (hatch, very thin ceiling joist Victorian property)

Please can someone in the know tell me what the minimum finishing height will be as it's not shown on the plans, although all other detailed measurements and materials to be used are clearly stated? Ive provided some details in the hope that someone can work the finish height out.

The plan says
Flat dormer roof –
membrane on 19mm ply on firings for falls 150 x 50mm joists at 400 c/c TRI ISO Super 10 insulation Counter battens Plasterboard and skim finish 70mm Kingspan between joists, ridge beam 2 No. 300x50+6mm plate.

ROOF
Upgrade front rafters to 125x50 sloping ceilings to allow for TRI-ISO super 10+ Insulation & 50mm air space. counter battens Plasterboard & skim finish. 75mm Kingspan Insulation.


LOFT FLOOR - Beam A 2 No. 225x50, Beam B 3 No. 300x50C24., Beam C 2 No. 300x50+10mm plate. Floor Joist 175x50mm at 400 c/c, 22mm Floor Boarding.

Thank you

Doozergirl

You're better off asking your architect! A cross section would have been nice as part of the plans, but if they've done the regs and the plans, they're the ones to know.

I know exactly what these things are, but there's no drawings to even start working out where they're positioned and this is simple for your architect.

System

Thanks

So there isn't a set rule for example, height minus new floor joist, minus gap between original existing ceiling joist, minus 22mm boarding, minus roof plasterboard and skim.

I believe all other measurements, battons, insulation etc is above the roof structure (Reroof) and kingspan is between the rafters which will be upgraded side to side so no height taken off due to any of them. Unless I am mistaken.

I don't understand the steel ridge beam and how much height that will take off, Please can you advise on the ridge beam?

Architect did plans a long time ago, date expires soon.

Thank you again

Doozergirl

To a degree, but I don't know where your steels are being inserted in relation to the ceiling joists.

I don't know what your existing rafter depths are or the pitch of the roof. The rafters need adding to in order to accommodate insulation and ventilation and your pitch will have huge impact in usable space in that area.

The dormer in its entirity needs to come level or below the existing ridge height, so everything above that you refer to would almost certainly impact inside.

The ridge beam is 300mm, so that will be its impact, but what exists?

Tri-Iso Super 10 has a mixed reputation. If you're having 150mm rafters then you could have 125mm Celotex (or similar) instead.

System

Hi Again,

The plan does have a cross section however this only shows a gable image of the dormer and the stairs, no height, although it states "floor with T&G Boarding, joist as calc's 100mm RW insulation laid between joists". It also states. At th bottom of the page it states 'Planning submission not as a working drawing... dimensions to be checked on site by contractor'. This is standard practice, I think, as I've seen it on lots of other plans when Googling etc.

Weren't in a rush. 2 years after having the plans done we decided to start on the loft but couldn't understand the plan I contacted the architect and explained that as there was no head height anywhere we were confused. He said normal practice and a builder will be able to understand it when he/she measures it for clarity. He kindly sent a PDF of the submitted plan with under eave height and dormer finished height which is 220 cm. Which is what we thought had been said when he actually measured up, and one that we were happy with.

Last week a reputable loft company called but said finished height is only 198cm at the end of the day it is what it is and I don't want to play anyone against each other but I just don't understand how there can be so much difference, 22cm! The loft company said that he comes across this all of the time hence the statement which is on the plan which is as standard I think '...drawing only for building regulations not as a working drawing...' I contacted the architect again, he isn't local anymore, said it was nearly 3 years ago, can't remember and just recalls the pitch being low for a Victorian property, so no help there. We've used the architect in the past for kitchen, conservatory, so find him OK.

Yesterday I went up the loft in frustration and got 238cm from under the ridge to the top of the existing ceiling joists which I was slightly disappointed with however 2 cm her or there is nothing but 22cm is. May be due to people measuring, etc. has made the loft more uneven in places as I also got 235cm in the middle of the room. We won't go ahead with 198cm as it may even devalue the property.

1) Can we get the full floor done, beams, joists, insulation and T&G done to the exact plan, and regulations so we can measure it again afterwards for an exact finish height, or do we have to contact local authority as we chose to go down the route of Full Plans Application with the Borough Council first, now that they have the plans etc ?

If it is only 198cm we'll just use it for storage, music room etc. with a loft ladder. This way it would be done to the plan for future owners who might be happy with the low head height and the dirty work done to Building Regulations, with a receipt of works done and before, during and after images to prove it. If it, anything above 200cm we definitely will convert it. Are we able to do this or do we have t contact building control who will charge a fee for the first inspection visit? However, once we've decided to take it further into a habitable room contact Building Control 2 days before the work begins, as stated on the plan... building owner to produce a method statement regarding safety of occupiers and employees during building work...

2) What will the Local Authority Building Control have to say about us doing the floor before informing them? We don't want to do anything illegal but obviously only want to pay the inspection fee and make contact when/if we have to do?

All legal tips and advice appreciated.

If any one else out there can contribute after experiencing the same during a loft conversion, or are actually in the building profession, please do as it will be much appreciated .

Thanks.

Doozergirl

My instinct highlighted that head height at pitch as being a bit troubling. There is a bit of an issue around building regs on the head height, so you need this clarified, really.

I'm sure your loft conversion man can stand in the space with you and the spec and tell you exactly how it will affect head height and where.

The option to get better head height is to remove all the ceilings and lower them. If it adds enough value to the house then it can be worth it, but I wouldn't fancy living in a house when Victorian ceilings come down.

teneighty

I'm baffled that anyone can produce Building Regulations drawings and not have all the relevant dimensions on the plan.

Anyway, the figures quoted do not make sense. In first post it is claimed there will be "235cm from under the ridge beam to the top of the floor." but in the last post it says the existing is "238cm from under the ridge to the top of the existing joists."

I would suggest that there is not enough headroom for a loft conversion unless as Doozer suggested you drop the existing ceilings or raise the ridge.

I would be thinking about getting my money back from the numpty "architect".

System

Hi again,

The joists are mostly in and we've placed a board on top of them and the ceiling height is going to be 225cm which we are more than happy with. I understand that different companies work in different ways. Phew!

French doors (Juliette) do come under permitted development but we are wondering whether to go ahead with them now, as I've heard a few bad reviews. They do look stunning but we ask are they practical.

Thanks for every ones help