Passive slab against party wall

[willbish]

I would like a raft on eps foundation for all the thermal performance reasons.

 

Our semi detached cottage will be demolished (planning permission permitting) leaving the front facade only and of course the party wall.

 

Can anyone foresee any problems with this scenario? Can the same perimeter insulation blocks be used internally against the party and front wall?

 

There will be a significant thermal bridge at these walls (even though the front wall will have EWI) is a passive slab even worth the expense...

[PeterW]

I’ve got to ask.....

 

why do  you need to leave the front facade if you’re using EWI as it won’t be seen ..!!

 

You may also have VAT issues - be careful !

[willbish]

I thought someone may ask that...

Well the project began as a renovation, and with each turn more of the original building has had to be replaced or altered beyond recognition.

 I’d like to keep the front facade so we can have the internal stone walls on show and deep window seats. So purely aesthetic reasons.

Yes regarding the VAT I’ve read closely what constitutes a new build, as far as I can see, it can be a new build if the party wall and one facade only remains.

[PeterW]

Ok - it’s a new build if, and only if, the planning permission instructs you to retain the facade wall. If not, you can end up as a very expensive restoration and no way to reclaim the VAT

 

I would knock the lot down and build the stone as a new inner thin skin

[willbish]

Yes retaining the facade needs to be an explicit condition of the planning permission. Perhaps I could take the new build designation topic to another thread.

 

 

It may well come to that!

Rebuilding with stone is pricey in terms of labour, would lose the deep window reveals and would look 'false'.

 

 

 

 

[Russell griffiths]

You think rebuilding with stone is dear. 

Wait until you try and tie the new building into the old one. 

Knock it all down and rebuild it replicating the deep windows and inner stone skin. 

 

I knocked down 3/4 of a house and rebuilt it, total pain should have flattened it and started again. 

 

Can you get the neigbours involved so you can both have a new place. 

[ProDave]

Can you think outside the box.

 

Having (almost) knocked it down, could you rebuild as a detached house? It would mean pointing / rendering the party wall to leave it as an outside wall for the other house. But think of the advantages of detached, even if it's only detached by 6 inches, no noise from the neighbour, worth more, etc etc.

 

The neighbour would not complain, his would also become detached.

[Jeremy Harris]

4 hours ago, willbish said:

Yes retaining the facade needs to be an explicit condition of the planning permission. Perhaps I could take the new build designation topic to another thread.

It may well come to that!

 

Rebuilding with stone is pricey in terms of labour, would lose the deep window reveals and would look 'false'.

 

No need to lose the deep reverals, with a stone skin you're going to get them by default, as the frames need to sit inside the insulation layer.

 

8 minutes ago, ProDave said:

Can you think outside the box.

 

Having (almost) knocked it down, could you rebuild as a detached house? It would mean pointing / rendering the party wall to leave it as an outside wall for the other house. But think of the advantages of detached, even if it's only detached by 6 inches, no noise from the neighbour, worth more, etc etc.

 

The neighbour would not complain, his would also become detached.

 

This sounds like a great idea with some compromise on loss of internal volume.  The benefits are significant, though, if you canget the planners to accept the idea.

Edited November 15, 2017 by JSHarris

[Onoff]

6" gap? You'll be rescuing dogs from that! 

[willbish]

18 hours ago, Russell griffiths said:

Can you get the neigbours involved so you can both have a new place. 

The new neighbours don't have any grand vision to remodel their side and have already started patching bits up.

 

17 hours ago, ProDave said:

Can you think outside the box

Nice idea, all for radical ideas, bit think this will compromise the internal living space of our small cottage too much. The current plans have already extended the footprint as far as possible in all directions.

 

There is a chimney breast in the party wall extending out 350mm plus the 6" gap plus new wall thickness ~400mm, over the depth of the property we'll be losing 6m2 internal footprint from the 86m2 we currently have.

 

 

Any thoughts on the EPS foundation blocks up against the party wall? I cant find any examples of it being done previously but cant see why not

 

 

[Gone West]

2 hours ago, willbish said:

Any thoughts on the EPS foundation blocks up against the party wall? I cant find any examples of it being done previously but cant see why not

 

Possibly there could be different types of movement between the two different types of foundations of the two semis which would cause problems with party wall cracking. All depends on ground conditions.

[willbish]

Was quoted today £17,700 for a passive slab ~90m2. Minimal ground-works, no drainage, no ufh.

 

£200m2 is more than I was expecting. How does this compare with what others have paid? Appreciate it may be difficult to separate slab costs from other ground-works and drainage.

 

Thanks

[ProDave]

£10K for strip foundations.

 

Obviously does not include the suspended timber floor, or the insulation that went into the timber floor and does not include UFH or any drainage work.

 

My cost is artificially low because I had my own digger at the time so I did all the digging and earth shifting.

 

I think what I am saying is your price does not look too bad.

[Gone West]

10 hours ago, willbish said:

Was quoted today £17,700 for a passive slab ~90m2. Minimal ground-works, no drainage, no ufh.

 

Our 90m2 Isoquick passive slab with 300mm of insulation was around £18000. This was with a 200mm thick reinforced concrete slab. It was around 50/50 materials and labour.

[willbish]

Thanks for that info.

 

What frustrated me yesterday was the gentleman I spoke to on the phone told me a passive raft slab was too expensive for my build. He told me that, after asking very precisely, what my total budget was. 

His dismissive attitude has just strengthened my resolve!