Terraced extension - fire regs

antiskeptic

I'm building a full-width-of-house, single storey extension to the rear of a terraced two storey property. The extension will mirror-image a full width extension built to one side next door.

My query concerns fire regs for my new side wall on the side bounding this to-be-mirrored extension.

I've been told my side wall has to be 9" solid (not cavity block or twin leaf) since the neighbours wall is but 6" solid on flat.

It seems 9" is the required firebreak between terraced buildings (and extensions by .. er .. extension). It has to be 9" solid continuous - not walls totting up to 9" or more in thickness - even if they butted right up to each other (say on raft foundations).

Is this the case?

Could anyone point me to the relevant reg?

Cheers.

Gumbo

antiskeptic wrote: »

I'm building a full-width-of-house, single storey extension to the rear of a terraced two storey property. The extension will mirror-image a full width extension built to one side next door.

My query concerns fire regs for my new side wall on the side bounding this to-be-mirrored extension.

I've been told my side wall has to be 9" solid (not cavity block or twin leaf) since the neighbours wall is but 6" solid on flat.

It seems 9" is the required firebreak between terraced buildings (and extensions by .. er .. extension). It has to be 9" solid continuous - not walls totting up to 9" or more in thickness - even if they butted right up to each other (say on raft foundations).

Is this the case?

Could anyone point me to the relevant reg?

Cheers.

Can you post a picture of the rear elevation.
Typically the 215mm solid block on the flat will be used where the 2 neighbours are sharing the wall and both build off either side.

If the neighbour already has an extension, then you will be building a new wall on the inside of your boundary, so in theory a cavity block wall in this location will comply, as would a twin leaf cavity wall construction type comply.

antiskeptic

kceire wrote: »

Can you post a picture of the rear elevation.
Typically the 215mm solid block on the flat will be used where the 2 neighbours are sharing the wall and both build off either side.

If the neighbour already has an extension, then you will be building a new wall on the inside of your boundary, so in theory a cavity block wall in this location will comply, as would a twin leaf cavity wall construction type comply.

There's not much to see at this point - we weatherproofed the side of his extension with plastic (for reasons below).

The neighbour's extension originally had the aforementioned 6"- on-flat wall as part of a cavity wall. The 6" was inner leaf on a raft foundation and a crumbling old garden wall on no foundation was used as the outer leaf (non structural / used to weatherproof the inner leaf/insulation). We demolished this outer wall with permission from the owner next door - so as to get our new wall near as possible to his.


A twist as of this evening. Stainless wall ties used during construction of the neighbour's extension (2001) were bent down along this side wall - they presumably couldn't be tied into the old mass concrete garden wall already existing. The ties were used only to retain the insulation.

A builder friend helping me has pointed out that these ties could be used to tie in my new side wall to the neighbour's wall. He's suggesting using 6" on flat for my wall tied in with the neighbours. Ample for a single storey extension he figures. It'd gain me some inches and save on foundations so worth considering too. It would put the new wall on the party line rather than on my side of the boundary but I don't envisage problems with the neighbour in that regard.

What thoughts on that?

And what factors would influence theory being fact in the original scenario up top

Thanks for the advice..

Gumbo

Creating a cavity between dwellings should not happen.
Without a picture is a drawing it's hard to visualise. Best to construct your own structural wall as it sounds messy.

What has your engineer suggested?

Gumbo

antiskeptic wrote: »

There's not much to see at this point - we weatherproofed the side of his extension with plastic (for reasons below).

The neighbour's extension originally had the aforementioned 6"- on-flat wall as part of a cavity wall. The 6" was inner leaf on a raft foundation and a crumbling old garden wall on no foundation was used as the outer leaf (non structural / used to weatherproof the inner leaf/insulation). We demolished this outer wall with permission from the owner next door - so as to get our new wall near as possible to his.


A twist as of this evening. Stainless wall ties used during construction of the neighbour's extension (2001) were bent down along this side wall - they presumably couldn't be tied into the old mass concrete garden wall already existing. The ties were used only to retain the insulation.

A builder friend helping me has pointed out that these ties could be used to tie in my new side wall to the neighbour's wall. He's suggesting using 6" on flat for my wall tied in with the neighbours. Ample for a single storey extension he figures. It'd gain me some inches and save on foundations so worth considering too. It would put the new wall on the party line rather than on my side of the boundary but I don't envisage problems with the neighbour in that regard.

What thoughts on that?

And what factors would influence theory being fact in the original scenario up top

Thanks for the advice..

6" (150mm) blocks would not be suitable for an extension in my opinion. I've only ever heard of he'd been used in small porches to the front.

At a minimum here you need 215 cavity blocks (if not connected to next door) or 215 solid blocks on flat. Depending on the roof profile, these walls need to take the loads from your roof and need to be disowned to do so.

Would need to see the arrangement on site to give proper guidance, hence the pic request.

antiskeptic

kceire wrote: »

6" (150mm) blocks would not be suitable for an extension in my opinion. I've only ever heard of he'd been used in small porches to the front.

At a minimum here you need 215 cavity blocks (if not connected to next door) or 215 solid blocks on flat. Depending on the roof profile, these walls need to take the loads from your roof and need to be disowned to do so.

Would need to see the arrangement on site to give proper guidance, hence the pic request.

Thanks for the direction kceire. In the end I figured to play it safe and go with certainty rather than perhaps-sis. 215 solid on flat it is..:)