Conservatory into an extention

khickey88

So I viewed a house yesterday which ticked most of the boxes. It had a large conservatory on the back which is integrated into the kitchen with no doors in between, the sellers told us that they have to fit a door between the kitchen and the conservatory and take the radiator out before we buy because of regulations. My question is how easy would it be to turn the conservatory into a proper extension and what sort of cost? One wall is from the original house the other wall is from the extension on the side from the kitchen and the other wall is been made up for the conservatory. I have left photos cheers

AdrianC

khickey88 said:

So I viewed a house yesterday which ticked most of the boxes. It had a large conservatory on the back which is integrated into the kitchen with no doors in between, the sellers told us that they have to fit a door between the kitchen and the conservatory and take the radiator out before we buy because of regulations. My question is how easy would it be to turn the conservatory into a proper extension and what sort of cost? One wall is from the original house the other wall is from the extension on the side from the kitchen and the other wall is been made up for the conservatory.

No, they don't HAVE to before selling. There's nothing to stop you agreeing to buy it in its current form. Sure, it wouldn't have had sign-off at the time it was done. How long ago was that?

To turn it into a "proper extension", you'd almost certainly need to demolish the current conservatory completely, and replace it with a properly insulated wall or window.

dimbo61

There are lots of companies who can replace the conservatory roof with a light weight insulated roof but it will make the rooms darker and little natural light in the lounge/dinning room

Davesnave

That would be horribly dark with a solid roof. If windows were added to compensate, what would they look out at? 

Most conservatory walls have foundations around 450mm deep. Building regs normally require 1m depth, so the added wall may be no use if you want to comply with building regs. What evidence do you have that the foundations would be adequate?

thearchitect

Foundation depth is dependent upon ground conditions.  In some areas 450mm is fine, in most 600mm.  I've only seen 1m a handful of times, where there was peat on site.

That's academic though.  Roof loadings are likely to be higher for a "proper" roof, even if lightweight, and of course their are insulation standards.  

In summary:  get an architect or building surveyor in.

Jeepers_Creepers

Wow - that's nice! 

Khickey, two of the walls are 'internal' so no insulation worries. The other wall - the one built for the connie - what's it made of? I presume blockwork, but what insulation does it have? If 'next to none', then this can be transformed by lining the inside with insulated plasterboard - I wouldn't bother going more than a 2" layer, as insulation savings fall away very quickly above that. (On our single-skinned garage wall, I added only 1" Jablite between the timber straps, and overboraded with 35mm TLB - it's the cosiest room in the house.)

The end windows and french doors - are they double-glazed? 

If all that is good, then only the roof needs attention. 

Ok, if you do this properly - architect, Building Regs, etc - it'll cost quite a bit. How much? I dunno - £20-£30k? Possibly more. 

What would I do? I'd let the current owner fit these internal doors and isolate (don't bother removing) the rad; it is now officially a 'connie', and I would treat this as improving the 'connie' rather than full BR compliance. At the end of the day, there will actually be very little difference in comfort and habitability in that room, but you should save quite a few £k in the process. The walls ain't going to fall down when you add a proper roof, because you'll use lightweight materials. 

Roof - find a good carpenter or roofing specialist if needed, and outline that this is an improvement to a connie, and not part of the main house. Therefore you want a lightweight timber construction whilst keeping it vaulted as it is - 4x2 rafters should do (tho' you might prefer 6"), cross-braced with timber collars (perhaps steel rods if you like that look?) to make attractive A-frames which will become an internal feature. Sterling board outer skin which is GRPed, with the guy adding vertical battens under it to give the appearance of a lead roof. Anthracite grey GRP. Add 4 skylights to keep the light level up - it won't be as bright as now, but - hey - they'll be clear so you'll see the stars through them. Make that 6 if you think you'll get away with it.

Cold roof construction - 2" of insulation cut to fit tightly between the rafters and flush with their lower surfaces, and then insulated plasterboard - say 45mm - to finish the inside. 

It won't conform with current BRegs, but it'll be perfectly warm and useable.  

Keep the doors until you are confident your local BCO ain't going to pay a visit. Then remove them and store in the garage - in case he turns up later... :-)

Davesnave

thearchitect said:

Foundation depth is dependent upon ground conditions.  In some areas 450mm is fine, in most 600mm.  I've only seen 1m a handful of times, where there was peat on site.

You call yourself an architect and I'm just an old bloke on the internet, but I read here often of  1m x 600mm being standard these days, varied  with the ground conditions, trees around etc. I've no reason to doubt that, having been involved with 3x foundations since 1987, all about 1m deep.

thearchitect

You're wrong.  Dig out a copy of Mitchell's, McKay, or Chudley .  A minimum of 450mm for frost cover, usually 600mm does it, as long as you're on a bearing stratum.

Davesnave

thearchitect said:

You're wrong.  Dig out a copy of Mitchell's, McKay, or Chudley .  A minimum of 450mm for frost cover, usually 600mm does it, as long as you're on a bearing stratum.

  I know what's often written here, what's written frequently in other forums and I know what was required when I built.

Maybe all those things are/were wrong, but the main thing I got wrong was saying what Building Regs require, when I should have said 'building inspectors.'

Jeepers_Creepers

Khickey, thinking about it, the job of sorting that roof doesn't have to be anywhere as complex as I said before. I'd now keep the existing roof and treat the project as one of two halves - the outside and the inside. For the former, simply have it battened and clad in lightweight interlocking tiles, something like this or similar (if you think it'll look ok):   https://www.roofingsuperstore.co.uk/product/lightweight-tiles-roof-tiles.html

On the inside get a joiner to install a number of timber rafters, A-framed as mentioned before, but these will be corballed or joist-hangered into the side walls; they will be self-supporting, sat tight against the underside of the existing roof, but largely independent of it. Make them nicely beefy - at least 6x2s. These will serve three purposes:
 
1) They will be used to support the DG skylights that you'll undoubtedly want inserted at regular intervals - 2 or 3 along each side? 
2) They will accommodate a couple of inches of celetox-type insulation sheet (leaving a small ventilated gap above them - it'll need ventilating out through the existing roof covering), and
3) look good; a vaulted timber-beamed ceiling with skylights. 

That's the 'gist', not a recipe. I'm just thinking that to transform this roof into an insulated covering to make that lovely room into a properly habitable space should be pretty straight-forward, and not even require a roof replacement - surely a giant saving.

thearchitect

I'm sorry but that advice somewhat oversimplifies matters.

Firstly, any roof requires to comply BS 6399: Part 3 (amongst other things) which sets out the requirements for both imposed loads and uplift.  The latter also comes under BS EN 1991-1-4:2005.  It will be necessary for a structural engineer to carry out these calculations, whether in practice or employed by a truss manufacturer.

Secondly, the walls themselves (including fixings for the rafters or trusses) must be able to carry the loads transmitted from the new roof.  Much will depend on the type and quality of construction, and on the foundations. Again, the advice of a structural engineer should be sought.

Thirdly, either building warrant must be sought (Scotland) or the work designed in accordance with the Building Regulations (England and Wales).  Insulation will be important.  A couple of inches of ever-flammable Celotex aren't going to meet current standards, and that's before we even get to issues around potential interstitial condensation.