wall cavity

[Aliyat]

Hello,

We live in a midterrace house with the half-width extension consisting of kitchen and bathroom at the rear. We are looking to extend and make extensions full width, which means it will be between rear extensions of two neighbours.

Initial extension was built in 60s or 50s wall when the requirement was 250mm wall cavity, whilst it is now 300mm due to higher insulation requirements. Whilst we are happy to have 300mm cavity on a new wall, we are a bit confused with existing wall. As our architect advised it is easier and cheaper to demolish the whole extension and build it from scratch because "Builders can charge more for fiddling around (because it is labour intensive) than for starting again. Concrete blocks are only 50p each and it wouldn't take them a day to replace the wall.", which we also understand but behind our existing wall is the neighbour's wall. It seems such unsustainable move to remove existing wall to comply with current regulations whilst there is neighbour's wall right behind together making up 500mm. Is there a regulation for cases like ours? We were also thinking to leave existing wall as it is by having full width extension for half length only? Please advise. Thank you.

 

[^woody^]

You would just insulate the existing wall

And sack your architect

If you remove a wall and build a new one, then there is potential to require new foundations too.

 

[pilsbury]

Also your architect has no idea on cost of blocks. Double that as a minimum.

 

[Aliyat]

Thank you! We are glad our simple logic wasn't wrong.

Application, however, has already been applied for planning permission (we are in the conservation area). Do we need to reapply or can we change this during Building Control stage?

Also could you please clarify how can it be insulated in our case?

Many thanks.

 

[^woody^]

Just change it. When the building inspector comes to check you can tell him or he can just check it when its built. It's not relevant to planning.

It would typically be lined with a foam insulation such as celotex or kingspa. Get your architect to specify and design this. Or the builder may just know how to.