Cavity wall question

[Bodgeitandleggit]

Hi, just a general question ,when a new house is being built is there a standard measurement of the cavity between the external and internal walls or is there a minimum/maximum range.......say the external brick is 100mm then cavity then internal block 100mm plus plasterboard and skim would you say the average thickness of a wall is 300mm -350mm

 

[^woody^]

The initial reason for cavity walls was to prevent dampness from the outer to inner face. No specific dimension was designed, but 50mm became the norm

Nowadays the thickness of the cavity is often related to the requirements for a certain amount or type of insulation to be put within it.

I would not say that the average wall thickness is 300-350mm - its still 250-300mm

You can build a timber frame wall to be much less thick than a masonry cavity wall

 

[jeds]

Cavity size in a standard house is determined by insulation requirement. 100mm has been common over the last 4 or 5 years.

 

[mravant]

Sorry to highjack the thread but what would you say is a better route to go in a block cavity:

1) 100mm drytherm
2) 75mm Kingspan with a 25mm air gap?

 

[noseall]

Sorry to highjack the thread but what would you say is a better route to go in a block cavity:

1) 100mm drytherm
2) 75mm Kingspan with a 25mm air gap?

 

[mravant]

Thanks.
Can you tell me the reasoning behind drytherm being better rather than using the Kingspan method?

 

[RonnyRaygun]

Some LABCs won't allow you to use 75mm Kingspan with a 25mm air gap. Where I live if you want to use Kingspan or Celotex a 50mm gap is the minimum they require.

 

[freddiemercurystwin]

Some LABCs won't allow you to use 75mm Kingspan with a 25mm air gap. Where I live if you want to use Kingspan or Celotex a 50mm gap is the minimum they require.

The clear cavity is dependent on your geographical area and the external render/block/brick finish, there's a chart in Part C that tells you what you can and cannot get away with.

 

[noseall]

Thanks.
Can you tell me the reasoning behind drytherm being better rather than using the Kingspan method?

'Tis easier to build.