Small loft space viability

[PSomm92]

Hi. We have a pre-war semi with a currently boarded out loft & limited loft height of around 190mm from top of boards to bottom of centre ridge. So plan to drop ceilings given are a generous 2.4m+ below. However, given cost/mess/complication as a result of an older style plaster, we would restrict to only a partial conversion for habitable space and as we only want a small box room for a child with a velux really and no one seems to want to do the job. This would be the area above the bathroom/ensuite in the pic attached, once a bedroom many years ago itself at 3.05x2.97m in size-though we would lose some with staircase/roof pitch of course but will work around with built in furniture/bed. Luckily have a nice big area in stairwell to continue staircase further up and in as depicted. Also preferring a door at top of staircase rather than bottom to keep open as possible-if allowed of course.



I've seen several guides online suggest for a small loft room (less than half of house. That you could possibly avoid any rsj’s ,etc. and just drop strong joists on hangers between the supporting inner walls and outer walls or even from outer wall to outer wall. Has anyone seen or done similar before I pay a structural engineer to go over in detail? We have two internal supporting walls and one external surrounding this area as per attached diagram. Will of course go through with structural eng,etc. before commencing a search for contractors. Many thanks.

 

[Bob Rathbone]

To drop the ceilings to 'steal' the extra room from a tall room is a good idea, BUT, the ceiling beams are the cross ties for the roof, preventing the roof weight pushing the walls outwards (lateral ties). Your suggestion would require the roof to be removed and new designed timberwork trusses to be installed, this is megabucks, are you really going to put out all of that cash to gain one extra room?

 

[PSomm92]

To drop the ceilings to 'steal' the extra room from a tall room is a good idea, BUT, the ceiling beams are the cross ties for the roof, preventing the roof weight pushing the walls outwards (lateral ties). Your suggestion would require the roof to be removed and new designed timberwork trusses to be installed, this is megabucks, are you really going to put out all of that cash to gain one extra room?

noted and thanks. Could new dropped stronger ceiling joists achieve the same if spanning instead across say the outer walls (so including the staircase area)? There are also large purlins on each side as this picture so guess I incorrectly assumed they would do most of the support and the area in centre could be dropped as long as done so using proper joist hangers/joists to.be structurally solid. Maybe steel is required afterall.

 

[Bob Rathbone]

No, you have missed the point. The ceiling beams are fixed to the wall plate and prevent the wall plate moving outwards due to the outward force exerted by the roof beams and the roof weight. Beams lower down will not prevent this movement as they are not fixed to the wall plate. The ONLY solution is to have new roof trusses designed and fitted according to the designers specification. Roof truss manufacturers will provide this service as part of the cost of the roof trusses. You need proper professional guidance on this, may be even a structural engineer. The purlins are installed mainly to prevent the roof beams sagging in the centre. Removing the ceiling beams from the wall plate will result in an unstable structure which is likely to fail....dramatically.

 

[stevie22]

The harsh reality here OP is that not every loft can be converted and you don't really have enough height overall to make it work sensibly even allowing for some clever engineering.

2.4m ceiling height is quite normal and to take a lot out of that would compromise those rooms. The fact that no one wants to do the job is significant.

I've just done a design for SWMBO's goddaughter (expensive wedding present!!). Starting from a 2300 headroom in the roof I wound up with a room height 2100 by dropping the floor by putting my new floor joists between the existing ceiling joists which therefore retained the tie function that Bob so ably described. Building Regs require no min room heigh but 2m in a corridor

In this instance the ground floor ceilings were 2740 max and several had been dropped previously to 2590 so there was no dramatic difference. We also had a dormer both sides of the front to rear ridge.

 

[PSomm92]

No, you have missed the point. The ceiling beams are fixed to the wall plate and prevent the wall plate moving outwards due to the outward force exerted by the roof beams and the roof weight. Beams lower down will not prevent this movement as they are not fixed to the wall plate. The ONLY solution is to have new roof trusses designed and fitted according to the designers specification. Roof truss manufacturers will provide this service as part of the cost of the roof trusses. You need proper professional guidance on this, may be even a structural engineer. The purlins are installed mainly to prevent the roof beams sagging in the centre. Removing the ceiling beams from the wall plate will result in an unstable structure which is likely to fail....dramatically.

Thanks Bob. I do get the point in terms of needing some form of cross tie. thanks. Never intended to have nothing there. Also Interesting as heard of several dropped ceiling jobs without new roofs entirely, Just lowered somehow, possibly using clever designs /support However. So will indeed seek further guidance just in case a structural guy can see any way considering as original post not all ceilings wll be dropped-around a third only so they may find a way to integrate that into the entirely of the strucures strengths with some additions.

 

[PSomm92]

https://www.loft-conversion-uk.com/lowering-the-ceiling.html

"Although not really something which needs to be considered in normal circumstances lowering the ceiling of the existing first floor is a viable alternative when the roof space is restricted.

The procedure for the job is to remove the existing joists and ceiling before installing new joists to form the new first floor ceiling / loft floor. This is a big task to undertake and is not simply a matter of whipping out a few joists and sticking new ones in.

First floor joists don’t just hold up the ceiling they also provide support to the roof. This is called tying and an alternative system will need to be installed if the ceiling is lowered.

Basically the new floor would need to be tied to the roof slopes by directly connecting new joists to existing rafters.

Although not a straight-forward carrying out the work will lead to more headroom in the roof space and therefore make a loft conversion more practical as well as increasing the design options for the project."

 

[Bob Rathbone]

Thanks Bob. I do get the point in terms of needing some form of cross tie. thanks. Never intended to have nothing there. Also Interesting as heard of several dropped ceiling jobs without new roofs entirely, Just lowered somehow, possibly using clever designs /support However. So will indeed seek further guidance just in case a structural guy can see any way considering as original post not all ceilings wll be dropped-around a third only so they may find a way to integrate that into the entirely of the strucures strengths with some additions.

You are very welcome, this will be a difficult and expensive job, tying the old roof to the new floor joists is not straightforward by any means, the forces on the connection of the two will be great, it will need designing by a good SE. Good luck.