Head Height

handyman11 · 3 Nov 2019

Hi I wonder if someone could tell me what amount of space is actually taken up with insulation, floor joists, plasterboard, floorboards etc when doing a loft conversion. I cant actually find what it would total, just lots of varying opinions on what original head height you need start with - some say 2.2m, some say 2.4m.

Our loft is 215cm and I did previously speak to a few people who said it would be possible to meet building regs in terms of head height at top of stairs (1.9m minimum). So I guess the question is what is the least amount of space it can be done in i.e. through putting joists in between ceiling joists, using the thinnest insulation permitted?

Lastly if head height cannot be achieved for sign-off, is there any implication of using the finished room (with stairs) as a den, library, or playroom, aside from not being able to call it a bedroom when selling? I presume there is no law against using it..

Thanks.

bobasd · 3 Nov 2019

OP, dont think about DIY'ing a loft conversion without drawings and SE's calcs and approvals- not even for what you call a "finished room".
or you will cause yourself quite a bit of difficulty.

the Regs protect you and more importantly: whoever comes behind you in the future.

Leofric · 3 Nov 2019

2m headroom over stairs unless roof slopes across from side of stairs .

handyman11 said:
Our loft is 215cm

from where to where

Difficult to say whether your property would be suitable for a loft conversion without knowing all the details. Anything below 2.2m ceiling height can be a bit oppressive but loft conversions usually have sloping ceilings

2.4m is the normal level ceiling height in houses.
As comments above ,don't do anything without approved drawings anyway.

tony1851 · 4 Nov 2019

You can drop the floor joists between the ceiling joists to gain an inch or so (though not always easy if stiffeners or wires are in the way).
Thicker joists/closer centres also help reduce joist depth.
In the roof, current thermal insulation regs require quite a big thickness of Kingspan, but where space is critical, you can thin this off
a little (private building inspectors are usually more flexible on this than council bods).

freddiemercurystwin · 4 Nov 2019

The thinnest floor I’ve ever done for a lofty where space was at an optimum was 18m deck + 150 joists + 15mm gap + 12mm plasterboard = 195mm. But the layout enabled the steel beams to be fairly slender and sit within the structural zone and the walls beneath were load-bearing so spans could be minimised.

As mentioned the pitched roof will need say 40mm insulation between the rafters and 90mm insulation + 12mm plasterboard beneath.

Dormers complicate things, adding a ridge beam and some insulation around it and a sloping dormer roof can eat into that valuable space.

Some roofs are just not tall enough to make practical conversions end of.

tony1851 · 4 Nov 2019

90mm below the rafters would be potty; the rules allow you to thin this off if it impacts on useable space.

handyman11 · 4 Nov 2019

The space height is 215cm from top of ceiling joist to underside of ridge beam. Thanks for the all the replies and point taken about not DIYing.
My main concern is whether I can achieve the required head height at top of stairs in order to get regs sign-off. If we got this, then we would not mind at all about the actual loft ceiling being low, as it would still be really usable space for us, whether as a play room, office or spare bedroom.

In terms of the 190 minimum, regs say this is applicable where roof above stairs is sloped. So does that mean if the roof was not sloped and you came up into a dormer that they would not permit 190?

Still unsure what amount I would be left with, though it sounds like 20cm is doable, which would mean head height at top of stairs of 195..

Leofric · 4 Nov 2019

handyman11 said:
The space height is 215cm from top of ceiling joist to underside of ridge beam.

Doesn't seem suitable for conversion to playroom, office or bedroom without adding dormers to give headroom to provide usable space. You usually look for a reasonable amount of floor area with 2m headroom in a room in the roof and you are only going to be able to achieve that over a very small area under the ridge.

handyman11 · 4 Nov 2019

To clarify I would want to add a small dormer yes. Whilst the space won't be huge and would have a low ceiling it would be a great benefit to us. Even without a dormer it would be of use to us. Question is whether we can meet regs for top of stairs 1.9/2m). Not sure about if 1.9m only applies if roof is sloped.

Leofric · 4 Nov 2019

Can you look on internet on LABC or Planning Portal website for Building Regulations ,Approved Document K stairs which shows the situations for headroom over stairs. That should give you the information you require.

tony1851 · 4 Nov 2019

For the stair headroom, you can put a drop-landing at the top, with one step up into the bedroom - if necessary on a right-angle turn; if you can achieve the 2m headroom above the drop landing, that should be OK. You can put a door in line with the step.
Also, refer to BS 5395 Stairs for Limited Access in Dwellings. This standard allows much steeper stairs for single-room loft conversions, which might help with your headroom issue. Not even many building inspectors are aware of this, and just stick rigidly to the 42-degree rule for new stairs.

Leofric · 4 Nov 2019

tony1851 said:
This standard allows much steeper stairs for single-room loft conversions

or alternating tread stairs - top to bottom in one go

tony1851 · 4 Nov 2019

Leofric said:
or alternating tread stairs - top to bottom in one go

Yeah, but a) they are dangerous, particularly for small kids, and b) when selling the house, it doesn't look as good as a conventional staircase.

handyman11 · 4 Nov 2019

tony1851 said:
For the stair headroom, you can put a drop-landing at the top, with one step up into the bedroom - if necessary on a right-angle turn; if you can achieve the 2m headroom above the drop landing, that should be OK. You can put a door in line with the step.
Also, refer to BS 5395 Stairs for Limited Access in Dwellings. This standard allows much steeper stairs for single-room loft conversions, which might help with your headroom issue. Not even many building inspectors are aware of this, and just stick rigidly to the 42-degree rule for new stairs.

That's really helpful Tony thank you and sounds like a real solution to the problem. I haven't seen anything written before indicating if you could have the landing a step down from the room. Given I am starting with 215cm and the rise of the step would be 20cm makes me think 2m is achievable for the top of the stairs (from 235). And when you say you can put a door in line with the step, how do you mean - would the door be flush at the top of the rise or set back i.e. so you have the rise and run, and then the door?

tony1851 · 4 Nov 2019

Door can be over the rise. It's not unsafe because a) safety can be gained by familiarity with the layout and b) the single rise is under the door which causes a person to stop, and then turn @ 90 degrees, thus slowing the user down and making them aware of the one-step down.

There's no hard-and-fast quantitative rule for stairs, other than that they should be safe, eg what is safe for a single-room loft in a single family dwelling, would not be safe in a 2,000 seat concert hall.

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Head Height

handyman11

bobasd

Leofric

tony1851

freddiemercurystwin

tony1851

handyman11

Leofric

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Leofric

tony1851

Leofric

tony1851

handyman11

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