Conservatory into an extention

khickey88

Thanks I had a little Google search and found a few companies that convert conservatory roofs into lightweight Thermoroof with skylights. Obviously keeping the doors in but do the  doors into the house have to be a certain standard of door?

Jeepers_Creepers

thearchitect said:

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.

I know I know I know...

But the whole idea is that the existing roof remains. Presumably that roof corresponds with BS whatevs or the connie equivalent. Either way, it's a recent roof that's already in place and it works. All he'll be effectively doing is adding a few A-frames that would be built independently of the original roof construction to carry the new skylights. You don't need an SE to know that if 4 or 6 A-frames and ditto skylights will bring the walls down, he's got much bigger issues. 

We are talking as many A-frames as are needed for whatever number of skylights - probably just 4 in that ~5m length (2 each side) so 4 A-frames hangered into the side walls but carrying nothing other than their own weight and that of the skylight. You are not going to tell me that this is going to bring the walls down.

The new internal roof will have lovely timber A-frames and clear glass skylights that'll allow beautiful shafts of sunlight through, and will be much better insulated. 

The alternative is as you say, but I won't even begin to add up the costs of checking the founds, underpinning them if necessary, and then constructing a whole new roof on top, but it'll be multiple tens of £ks. 

Hey, it's just an idea. But to remove that existing roof and replace it with a 'proper' one is going to cost big.

I doubt very much the OP will entertain my idea tho'... :-)

AdrianC

khickey88 said:

...but do the  doors into the house have to be a certain standard of door?

Basically, regard the conservatory as "outside" - so they want to be exterior-grade.

snowcat75

Davesnave said:

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.

Id agree 100% there would be zero point in even getting BC out around here to inspect at 600mm they would just tell you to go down another 400mm min, even at 1000mm there likely to want a further 250mm.... and even at 1250mm they may want bar in there as well....
That's real world building vs what the book says.

thearchitect

Someone better tell NHBC then, get then to change their guidance too, what with that having a table showing different foundation depths depending on the soil types. And the Scottish BSD, they'll need to change their small buildings guidance.......and the NI regs, which say 450mm.

You see, the important bit you've overlooked is the need for a suitable strata or solum.  In the south of England, you have highly plastic clays which shrink under certain conditions.  In much of the rest of the UK, we have medium to heavy clays which are stable.  Therefore frost cover is the key issue (generally 450mm) or dealing with soft spots.

But what would I know, I'm only a chartered architect. 

Incidentally you need to use trench fill at depths much over 750mm, unless you want a lot of benching off or use bracing, making things very expensive.  And popping in a layer of steel mesh has been common for the last thirty years or so as it bridges any localised defects.  A142 or A252 are typical.

Davesnave

Where's Doozergirl when I need her?

snowcat75

thearchitect said:

Someone better tell NHBC then, get then to change their guidance too, what with that having a table showing different foundation depths depending on the soil types. And the Scottish BSD, they'll need to change their small buildings guidance.......and the NI regs, which say 450mm.

You see, the important bit you've overlooked is the need for a suitable strata or solum.  In the south of England, you have highly plastic clays which shrink under certain conditions.  In much of the rest of the UK, we have medium to heavy clays which are stable.  Therefore frost cover is the key issue (generally 450mm) or dealing with soft spots.

But what would I know, I'm only a chartered architect. 

Incidentally you need to use trench fill at depths much over 750mm, unless you want a lot of benching off or use bracing, making things very expensive.  And popping in a layer of steel mesh has been common for the last thirty years or so as it bridges any localised defects.  A142 or A252 are typical.

Likewise we also have pockets of pure ballast a lot of stones pulled out from the SE, I grew up from a farming background so am pretty good at understanding soil types, possibly even better than an chartered architect 

No matter what's down there our local BC always wants a min of a 1000mm..... simple as and iv done a reasonable amount of building work  
I understand what the recommended can say but attempt to argue that with a local authority that has a blanket policy.

and btw locally we don't even put foundations onto the proper blue clays that pocket the estuary's its all rafted.

thearchitect

Have you considered that perhaps you just live in an area with excessively plastic clays?

Incidentally, some blue clays are expansive which can lead to problems.

snowcat75

thearchitect said:

Have you considered that perhaps you just live in an area with excessively plastic clays?

Incidentally, some blue clays are expansive which can lead to problems.

I'm sited on a 3500 acre shelf pushed here by the ice age which has just over a 100' of ballast bellow a 5" overburden, the 100 acres of historic gravel extraction are a hint, and certainly failing another ice age pushing one of the estuary's over the high ground there's not a drop of clay down there.... but good luck arguing with BC for a 600mm footing.

Jumblebumble

Jeepers_Creepers said:

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... :-)

We put in a false ceiling in our conservatory a few years ago with removable hatches into the roof space for the summer
We specified very good lighting 
This cost less than 2K all in and has made it usable beyond all expectations
It does make the living room a bit dark but we are not bothered
I could not care less about BR as it is our forever home and all work  could be reversed in a couple of hours
The job was done by a professional roofing company ( although the roof was not touched)