Balancing room heights and loft conversion

[Sjk]

Hi all

 

I have proposed ridge height of 7.75m, eaves 5m, maybe we could get away with cheekily pushing the ridge to 8m..

 

Going to use 195mm easijoists, so estimate the total floor widths would be 300mm, and I believe the standard ceiling height is 2.4m, so that leaves very approximately 2m of height for the loft.

 

Now I'm wondering if it would be wise to reduce the ceiling height to 2.3m or perhaps keep 2.4m on the ground floor and reduce the first floor height as it only has bedrooms/bathroom.

 

Any thoughts? The loft is a must as need the extra bedroom.

Edited March 23, 2019 by Sjk

[Sjk]

Maybe I can get the floor widths down to 250mm, an 10cm would help. 

 

Wonder realistically how high I could push the ridge height undetected. ?

[Lesgrandepotato]

You can play with this internally without really anyone noticing. We converted an existing building so the internal height was set. With the room sizes downstairs we wanted more height (room is 10 * 4m) then double height. We wanted to feel high, so we went to 2200mm on the French doors, and 2350 on the front doors. The height here is 2480.  The upstairs lounge is 8 * 4 so we wanted to keep a decent height this is 2400. 

The bedrooms / bathrooms are all around 2340 or so. They all feel right, but I wouldn’t put a big room with a low ceiling. 

 

We also focused on taking out all downstands to give an illusion of height, and further to this deleted all the ceiling roses to again drive this illusion. 

[ProDave]

What are you trying to achieve with the "loft"?  Another floor of habitable space? Or just a storage area that you can stand up in?

 

If you can't raise the ridge height, can you lower the ground floor level?

[Ferdinand]

The above is correct, think about your loft purpose. .. is it storage or habitable.

 

The assessed floor area depends on a height which will exclude some of your slope. That applies to eg minimum bedroom sizes in my world, but will also apply in some ways to Yours.

 

F

[Sjk]

Sorry should have said it’s the 3rd bedroom with an en-suite. 

[ProDave]

If it's a bedroom you will have very little standing room unless you incorporate a large dormer windows(s)

[Sjk]

Yeah it’s not going to be easy but that’s the challenge. Hopefully shaving off cms here and there will make all the difference. 

[Sjk]

I wonder how much space is taken up by the width of the roof, ie tiles, rafters, insulation etc. 

[Russell griffiths]

1 hour ago, Sjk said:

I wonder how much space is taken up by the width of the roof, ie tiles, rafters, insulation etc. 

260-300mm

[PeterW]

Need to know how wide this is as that will also affect the space. What’s the full span from wall to wall across the apex..?? 

[PeterW]

@Sjk think your maths may be wrong ...

 

floor depth will be 230mm total with 195+22+12.5 so you could do 2.3m ground and 2.2m first floor and still get 2.4m to the bottom of the ridge board in the upstairs. Issue would be the width and the pitch of the roof that will give you the problem areas - anything less than 1.6m height is only really good for storage. 

[TerryE]

We've got living space in our loft as well, with a lot of complaints from neighbours re the ridge height so we went through a lot of similar hassles balancing the build up of the levels to ridge height.  Our house works with no complaints, but our ridge height still worked out at 8640, and IIRC this gives us around a 1.6m ridge corridor with head clearance above 1.9m but we also have a rear gable in my son's bedsit and the T head clearance makes the whole space workable.

 

In my previous house we converted a barn extension into a split 1½ storey living area with the other half a kitchen and sleeping area above.  The sleeping area was quite spacious (I used it as an office when I still worked), but it was a real PITA only having a ~30cm ridge corridor where I could walk without stooping -- and when we came to sell the property, the estate agents wouldn't classify it as a bedroom because of the head-height.

 

So some points to consider:

• We had a rise from the road access to the house of ~0.7m.  We did a lot of relevelling and removed ~400-500 tonnes of subsoil off site to allow us drop the ground level to road + 0.1m or FFL to road + 0.25m which gave us another 0.45m to play with relative to the street scene profiles.  You might consider MMA options to do something similar.
• Our room heights are 2.4m (ground floor) and 2.3m (1st floor).  The 2.3 works fine and doesn't feel limiting.
• You need to be very careful about ridge height if this is an issue locally.  The last thing that you want is for planning enforcement to pick this up and put a stop order on you and force you to do major rework.  This is a judgment call but have a look at other enforcement actions and precedent before deciding that an extra 250mm is a cheeky shoe-in.
• Having a gable in-roof to create a T ridge in the main loft room can significantly increase the effective head-height area.
• Having interior load bearing walls can allow you to replan your joist layouts and dramatically reduce joist depth.
• Do a very detailed profile of the roof build-up.  In our case we have a passive-class warm roof: I beam ridge, with 300mm rafters and insulation, 25mm service cavity and 15mm pboard on the inside; 18mm sarking, counter battening and battening + slate on the outside -- all × 1.41 in height terms because of the 45% pitch. Add the air breathing ridge capping and this buildup  is over 0.5m.
• If you have (dummy) gable chimneys then consider other options such as having a flattened ridge.

The dilemma here is deciding how much to share with the LPA in trying to evaluate options, and this is something that we and your planning consultant will need to evaluate in the local context.  We found pre-planning advice extremely useful in getting the LPA support, but other members here can tell nightmare stories.

Edited March 24, 2019 by TerryE

[Sjk]

Thanks all for the replies I’ll have a good read later. 

 

The overall footprint is 6.2m by 9.3m, ridge is 7.75m and eaves 5m. 

 

 

Edited March 24, 2019 by Sjk

[Lesgrandepotato]

I can’t take all the credit for ours, it was driven by finding a structural engineer who was up for solving the problem creatively. We ended up with a step in the landing but it’s a worthy compromise 

[Sjk]

Im wondering if i can have a higher ridge height at the rear.. Not sure how the planners would react to that.

[Lesgrandepotato]

Is the site flat? We need to know where that datum comes from. A 12” slope could find you the space you need. 

[TerryE]

14 hours ago, Sjk said:

I am wondering if i can have a higher ridge height at the rear.

 

They typically work off the street scene, though the rear height can be relevant if you have neighbours near.  If your plot does fall away from the road, then setting the house down relative to the road is an important option that you should explore, as well as having gables.   More work yes, but you also need to consider that the increased market value of a house having loft rooms that comply with the requirements for bedroom space.

[oldkettle]

On 24/03/2019 at 13:16, PeterW said:

@Sjk think your maths may be wrong ...

 

floor depth will be 230mm total with 195+22+12.5 so you could do 2.3m ground and 2.2m first floor and still get 2.4m to the bottom of the ridge board in the upstairs. Issue would be the width and the pitch of the roof that will give you the problem areas - anything less than 1.6m height is only really good for storage. 

@PeterW, this total of 230mm, does it include any floor finish? Sounds like plasterboard plus joists plus chipboard? 

[PeterW]

13 minutes ago, oldkettle said:

@PeterW, this total of 230mm, does it include any floor finish? Sounds like plasterboard plus joists plus chipboard? 

 

Correct as you don’t allow for this in a build up. 195 joist plus 22mm chipboard, 10-13mm plasterboard is standard. 

[oldkettle]

47 minutes ago, PeterW said:

 

Correct as you don’t allow for this in a build up. 195 joist plus 22mm chipboard, 10-13mm plasterboard is standard. 

 

Thank you, Peter. Does it mean that the real ceiling height is usually lower than quoted, i.e. 2400mm (quoted) -15mm of engineering wood or similar?

[PeterW]

Yep absolutely. Final finishing can be pretty much anything from 2mm Lino to 25mm stone. 

[Sjk]

Thanks chaps. 

 

The sides pretty level, definitely need topo survey done. 

[Lesgrandepotato]

Any chance of a floor plan so we have more vicarious building thrills while trying to solve?

[Bitpipe]

On 24/03/2019 at 13:34, TerryE said:

We've got living space in our loft as well, with a lot of complaints from neighbours re the ridge height so we went through a lot of similar hassles balancing the build up of the levels to ridge height.  Our house works with no complaints, but our ridge height still worked out at 8640, and IIRC this gives us around a 1.6m ridge corridor with head clearance above 1.9m but we also have a rear gable in my son's bedsit and the T head clearance makes the whole space workable.

 

Very similar situation to us. I agonised over room heights and got very upset when the ground floor needed extra battening to even out the ceiling line from a rogue steel.

 

However, we have 2370mm downstairs from FFL to ceiling and 2275mm on first floor. Room in roof is 2500 to apex and 1600 to the top of the velux windows.

 

All works fine and does not feel at all low. Basement is 2700mm and that almost feels too high by comparison. We have some narrow floor to ceiling windows downstairs and went with metric doors (2040mm) which all work to make the ceiling look higher (did not plan this effect, pleasant surprise).

 

We also dropped the GF level by 100mm to steal some extra height once we had the detailed drawings with floor and roof buildups - main concern was the street level sewer invert and how this played back to the ground floor wastes, getting the necessary falls etc. French drains at the perimeter allayed any worries of surface water running back to the house.