Insulate Gable Wall over stairs

wicklah

Hi,

I've been reading up on the various types of insulation to attempt to insulate my 9" cavity (1970's) 3 bed semi. There is no external wall insulation on the house (cold winter house therefore).

Now I've no problem drylining inside the various rooms around the house, but what I want to know is what to do over the stairs. They are attached to the gable wall. If I put in 4" of drylining here, it is going to encroach on the stairwell (probably therefore breaking building regs). I will not be pumping the cavity blocks as that will not help from my reading on SEI. I also do not want to external faced insulation if possible, but if it is the only method then I will go for it.

Anyone any ideas?

Thanks

Mellor

How wide is the stairs currently?

wicklah

Hi Mellor,

It's:

WALL | a | b | c |

Where: a = 25mm wood side of stairs
b = 845mm thread of stair
c = 30mm wood edge.

Open bannisters up to first floor level.

Thanks

sinnerboy

wiklah - this is always a tricky one

Try
1. using 25+12 CPB ( composite platerboard ) this will take the CPB 12mm past the face of the string ( side of stairs , like skirting board )
2. cut a new string from 12mm mdf and plant over old . Use a moulded timer plant at join

hope this works for you

Mellor

sinnerboy wrote: »

wiklah - this is always a tricky one

Try
1. using 25+12 CPB ( composite platerboard ) this will take the CPB 12mm past the face of the string ( side of stairs , like skirting board )
2. cut a new string from 12mm mdf and plant over old . Use a moulded timer plant at join

hope this works for you

Thats a possible method of carrying out the work, but it doesn't really answer the OPs question.

wiklah, you are concerned about building up the wall and reducing the stairs width below that allowable in the building regs.

From the widths here:

WALL | a | b | c |

Where: a = 25mm wood side of stairs
b = 845mm thread of stair
c = 30mm wood edge.

The distance between the inner face to the outer string and the wall is 870mm (a+b).
Assuming the handrail to the wall to similar to this distance, (it may be < or > this dimension depending on design of balustrade), you have a little room to play with. The minimum width of a private stairs is 800mm, this gives you about 70mm to work with (measure from the inside of the handrail to the wall for more accurate distance).
So best option here is 50-60mm insulation (phenolic or similar) and 10 or 12mm plasterboard.

The simply fact of the matter is you may start to encroach on the stairs requirement in the regs, but if you don't carry out this work you are failing part L (energy) of the regs. Strictly speaking the regs don't apply to a 1970s house, but they do apply to any work carried out.

wicklah

Okay, from edge of newell post to wall is 842mm.

So in theory I could get away with something like "Kingspan Thermawall TW52 zero ODP" width: 37.5mm from http://www.insulation.kingspan.com/uk/pdf/tw52.pdf (for example). When that is skimmed then I'll be close enough to regs.

Uvalues isn't great on it (0.57) but gotta be better than uninsulated wall (be interesting to know what the actual uvalue is of my existing walls).

I suppose the only other alternative is to externally insulate it. From my reading of this forum and others, the jurys out about it (poroton and the like). Would probably make more sense from a space point of view. Hmmm, not sure what to do.

sinnerboy

Just be practical . In consideration of compliance with regs does ( in preambles part of TGD L ) recognise that in the case of existing buildings that not all recomendations "may be appropriate". . Use 38mm CPB

Mellor

wicklah wrote: »

Okay, from edge of newell post to wall is 842mm.

So in theory I could get away with something like "Kingspan Thermawall TW52 zero ODP" width: 37.5mm from http://www.insulation.kingspan.com/uk/pdf/tw52.pdf (for example). When that is skimmed then I'll be close enough to regs.

Uvalues isn't great on it (0.57) but gotta be better than uninsulated wall (be interesting to know what the actual uvalue is of my existing walls).

I suppose the only other alternative is to externally insulate it. From my reading of this forum and others, the jurys out about it (poroton and the like). Would probably make more sense from a space point of view. Hmmm, not sure what to do.

Whats the width at the handrail?
Don't be afraid to step inside the 800mm limit.
External insulation is an option, but bare in mind that you would have to do the whole house as you will run into huge cold bridges where internal insulation section meets external insulation section etc

wicklah

Thanks for the replies fellas, appreciate it.