Wall design for rear extension to maximise space

[JamesWins]

Hi

Getting an extension planned out and need some advice on how to get the most of the available space. I live in a terraced townhouse which 4200mm across (narrow innit) and want to put a 4m oak framed garden room on the back with a pitched roof.

Story time... We're hemmed in by neighbours extensions on either side which are mono-pitched but only about 3m long so can't follow their roof line, besides we want the higher ceiling space. Usually with a garden room the whole thing is built of oak pillars and the sides are fully glazed but there wouldn't be much point so the far end will be fully glazed with french doors and the side walls will just be solid masonry. There should still be plenty of light once we've got a couple of Veluxes in the roof, plus the garden is south-facing.

So assuming you're still awake after that, here's the problem. The architect (works for the oak company) is saying we need 300mm walls at the side (pretty standard) and this is in addition to a 175mm gap for guttering at either side (due to pitched roof design). So 4200 - 350 - 600 = 3250mm which leaves the extension significantly narrower than the kitchen it will join on to.

I've asked building control and they said we might be able to go to 250mm with a masonry cavity wall but that only saves 100mm.

I was wondering about insulated panels/ SIPs but the designers says (someone else told me the same) you can't install panels without access to both sides of the wall... anyone know if that's true?

Any other ideas?

 

[^woody^]

Get a new Architect.

When infilling, you use the existing neighbouring walls and so only need minimal thickness for the purpose of insulation and finishes, or no insualtion if the adjacent space is heated. You don't need to worry about exposure or weathering.
Where this needs to be come an external wall above the roof line then it can be changed at that level - but appearance wise it depends if it can be incorporated into the design.

Minimum thickness of a shared wall can be 15mm for plaster, for a sheltered wall will be less than 100mm. For an exposed, about 150mm.

Using the neighbours wall may involve serving notice under the Party Wall Act

 

[JamesWins]

^Woody^ as I say, the neighbour's walls are monopitched and only about 3m (on one side, the other side is only a 2m lean-to) so we'd struggle to build off them. We could change our design to monopitch as well but then we'd have to either shorten the extension or lose headroom at the end - would look pokey.

I suppose what I'm asking is, how to make a timber frame wall with only access to one side.

 

[wessex101]

As for the 175mm gap for guttering, that make no sense if you are pushed for space. Just build the flank walls right up to the boundary and have a parapet wall and tapered box gutter so that you do not need any eaves over hang.

I cannot really see the point of a small oak framed extension unless the existing house is oak framed. You could achieve the same affect with some feature oak trusses in a vaulted roof for a fraction of the cost.

Likewise I think SIPs panels are over rated unless you are self building a house, and even then I'm not a fan.

 

[^woody^]

I suppose what I'm asking is, how to make a timber frame wall with only access to one side.

You build the panel and place it against the neighbours wall. Flash the roof junction as necessary and add weather cladding to parts of the frame that are external.

 

[JamesWins]

As for the 175mm gap for guttering, that make no sense if you are pushed for space. Just build the flank walls right up to the boundary and have a parapet wall and tapered box gutter so that you do not need any eaves over hang.

I cannot really see the point of a small oak framed extension unless the existing house is oak framed. You could achieve the same affect with some feature oak trusses in a vaulted roof for a fraction of the cost.

Well, the idea is to have the whole end glazed and I haven't seen any architects or builders offering that kind of thing, except the oak firms. It won't be very expensive, under 15k (because they're only really doing the end and the cross member) and will look really nice, we've seen one and my wife loved it.

I think it's a good idea to build the gutter into the roof, I'm going to run it past the architect. That'd save us 300m, which is a lot. Cheers!

 

[Footsoldier888]

It seems a little odd that a mediaeval building technique is the only way to hang some glazing. I know the building trade moves slowly but is that really true???!!!

 

[JamesWins]

It seems a little odd that a mediaeval building technique is the only way to hang some glazing. I know the building trade moves slowly but is that really true???!!!

Well the end results will be something like this (just not glazed at the sides) and I genuinely haven't seen anything on the market along those lines aside from the oak firms. Wouldn't want it to be all aluminium frames and if its external structural timber that means oak, pretty much?

If you can suggest alternatives (pictures would help) then that'd be handy.

The architect I had previously just wanted to do a flat roof with a bi-fold at the end and I think that's pretty **** (no offence to anyone with that kind of setup).

 

[^woody^]

Its aluminium or [medieval] timber frames for glazing.

That oak work is really for the feature of thick frames rather than necessity, as typically for a glazed facade the frame would ideally be as thin as possible, otherwise a timber frame section could be formed which would be much narrower than that oak frame.

It's whatever floats your boat, and whether oak or aluminium actually harmonises with the existing property is always going to be subjective unless the main house is of the same material.

 

[tomfe]

Each to your their own James, but that addon you linked to is not really in keeping with any elements around it, it has a slate roof etc it just looks stuck on. But if that's what you are going for....

The architect I had previously just wanted to do a flat roof with a bi-fold at the end and I think that's pretty ****

I am going to presume those stars are replacing the word 'standard'.

 

[tomfe]

Its aluminium or [medieval] timber frames for glazing.

or structual glazing

 

[JamesWins]

Each to your their own James, but that addon you linked to is not really in keeping with any elements around it, it has a slate roof etc it just looks stuck on. But if that's what you are going for....

It's a fair comment about that particular extension, which does look stuck on - I just googled it up. Our house, as I say, is a victorian townhouse and we think it'll look a lot better than that. We might struggle to blend in unless you can recommend someone who works in ashlar limestone facades...

You're right it's a matter of taste but if you haven't been in one of those oak garden room things then try one out, they're pretty lush.

I am going to presume those stars are replacing the word 'standard'.

Not exactly. BTW are we not allowed to swear on the internet now? What is the world coming too.

 

[^woody^]

or structual glazing

Yes if you want the retail look.

 

[^woody^]

It's a fair comment about that particular extension, which does look stuck on - I just googled it up. Our house, as I say, is a victorian townhouse and we think it'll look a lot better than that. We might struggle to blend in unless you can recommend someone who works in ashlar limestone facades...

You're right it's a matter of taste but if you haven't been in one of those oak garden room things then try one out, they're pretty lush.

The key thing is to get the extension to harmonise rather than to match. The two are different concepts, and dissimilar materials and construction can work well together if designed properly. The key thing is to avoid the "stuck on" approach.

 

[Footsoldier888]

I was only meaning to have a gentle joke James. I have seen oak look stunning with Viccy houses and am a fan myself. My point was you can use steel or wood to achieve that look, it doesn't have to be oak for structural reasons was all I was meaning.

They even do frameless glass now if you want to really push the boat out.