Conservatory floor/foundation issues

[Christian McArdle]

How important is it to do the foundations right for a conservatory? It will go over an area that is currently half concrete slab (looks thin) and bricks (a bit wobbly). Can I just get some concrete over the whole lot to level and strengthen it, or do I need to do some serious digging? The sides would be wooden. I want to use the room as a dining room, as it is right next to the kitchen.

The back garden has no access except through the house. It is not possible to get large pieces of equipment to the rear. Is it possible to have ready mixed concrete pumped through the house through a hose? Obviously the quantities required aren't huge, but I don't think you'd get a mixer round the back. A full wheelbarrow is out of the question as there is a sharp turn and newly sanded and varnished floors. You'd need to upend it to get round the corner.

One edge of the conservatory may form the boundary, replacing a rotten fence. Windows on that side would be painted out, or replaced with ply. Does this complicate the issue, as this wall would be right on the edge of the slab? I could build just up to the fence, and just take the fence panel down when maintaining. This will probably be at the neighbours option.

Christian.

[Christian McArdle]

I thought conservatories were a specific exemption to this. Does anyone know for certain?

In case it makes a differerence, the floor area of proposed conservatory is approximately 11m2. The ground floor area of house (terraced) is about 36m2, giving approx 72m2 total area on two floors.

Christian.

[Christian McArdle]

It would be as easy to get a ocean liner through the house as a mini digger or concrete mixer. Anything of that size would need to be craned in over the house.

I suppose you could get one of those tiny mini mixers in, but it would take an age to make up the required amount and it couldn't be done in one pour, so would presumably be very weak.

Christian.

[Nick Finnigan]

You certainly can get concrete pumpers - a house near me had the solid ground floors re-made using one. IIRC it had a truck with some hydaulic extending supports to get into the house, and then flexible pipes to go inside the house. I don't know where from or how much, but I'd expect a hefty minimum charge.

[Peter Crosland]

You will need both planning permission and building regulations approval if the conservatory is attached to the house and it exceeds 10% of the existing floor area. Note that because it is a terraced property the size limits are smaller.

[Christian McArdle]

Apparently, though, the 10% applies within a range from 50m3 to 115m3, so the minimum permitted development rights are 50m3, however small the house.

A very rough estimate of volume is 3 x 3.5 x 3m, which gives 31.5m3, well within the limits and enough left over for a lean-to over the side of the kitchen. The house was built in 1909 and there has been no previous extensions, just a garden shed, not attached in excess of 5m away from where the conservatory would end.

For building regulations, different rules apply, based on a 30m2 floor area. Total area will be about 10.5m2.

So I can't see why I'd need Planning Permission or Building Regulations approval.

Christian.

[Toby]

You would be suprised at how much comes out of a mini mix tripod type mixer in a day, the only struggle is getting all the materials close by. I wheel mine through the house OK (90deg corners et al) although it's also possible to carry it, goes in the back of a small car with the seats down. If it's a really tight fit, you can remove the drum from a Belle 150.

If you were to mix the foundation for the curtain walling, and the base on separate days, you would possibly get away with a weekend hire.

A house built as infill behind existing houses 400m from here had a pumped foundation, the contractors turned up with what looked like enough kit to build a motorway and *unanounced* closed/blocked the road, until a small contingent of neighbours pointed out that they still needed to get to work somehow. The mixer, pump lorry, and gantry/rig/crew lorry stayed out the front of the site, the vertical gantry was built up out the back to form a high point for the operators to swing the nozzle about from. It did not look cheap. I havn't seen a smaller version of this anywhere, and it doesn't seem to be in my plant hire brochure as an option.

Toby.

[Peter Crosland]

Apologies I have misread it! I thought the 10% was a lower figure for terraced properties. I also assume your house is not in a conservation area.

AFAIUI Building regs will apply since it is an extension. The best thing is to talk to BCO before you do the work since it can be incredibly expensive to correct. Don't forget the new rules on insulation standards if you are DIYing the conservatory. You WILL need approval for that unless it is installed by a FENSTRA registree.

[Tony Bryer]

The limiting factor is how much you can shovel in a day - a bigger mixer just means fewer larger batches. When I did my foundations I arranged things so that my Belle Minimix (on swivel stand) was positioned so as to tip straight into the section being concreted, and my pile of ballast likewise to go straight into the mixer. You'd be surprised how much you can do in a day if things are in the right place.

[Christian McArdle]

It is. Non-terraced properties seem to get 15% between 70m3 and 115m3. Mine falls off the bottom anyway, though, hitting the 50m3 minimum. As an Edwardian building, it has no restriction on permitted development rights that has been common on more recent estate conveyances.

OTOH, I don't want to use too much permitted rights up. I'm thinking of a dormer rear roof extension if it can be made to look OK. A quick back of envelope calculation shows 20m3, so it'll be marginal and probably require PP, especially if the lean to is constructed. I probably overcooked the estimate on the conservatory so could probably squeeze both in.

I still think not. Conservatories below 30m2 floor area appear to be exempt, with loads of conditions that aren't too onerous. It needs to have a transparent roof, 75% glazed walls, a proper external door between it and the house, seperately zoned and controlled heating (if heated), below a certain height etc.

Christian.

[Grunff]

It certainly is a heft minimum charge - I was recently quoted £800 to hire the pumping gear for one day. This didn't include the concrete.

[Christian McArdle]

Oh. Are the new conditions really bad?

What about flammability? It's going to be wood and on the boundary.

Christian.

[Christian McArdle]

I'm going to insulate anyway. But there is no way a conservatory would meet general building regulations. Perhaps the exemption is finished, but only a tiny subset of rules apply?

Christian.

[BigWallop]

This should explain a bit more about it:

[Peter Crosland]

Let me make it a bit clearer. Yes the standards for conservatories is lower than other extensions. This does not alter the fact that they are, if attached to the main house, subject to building regulations approval.

[Michael McNeil]

Any building stands or falls according to its foundations. But why are you considereing a slab for what is only going to be a lean to? Get a bore hole auger from a toolhire shop. If the ground is suitable they work fine if not hard luck. Test it and see. What would it cost to hire one for a day? a few quid.

Now you can pour concrete piles or sink bitumin treated wooden ones. If you buy them long enough they will make the sides of your dining room. Put them in a window wide apart or whatever and there you are

-built in the time it takes to lay the concrete.

[Andy Hall]

That isn't what the Statutory Instrument says.....

In the Approved Document to Section L1, paragraphs 1.58 to 1.62 apply and there is a difference when the conservatory is attached to a new building vs. an existing one. With a new building, there would be Building Control involvement anyway.

The situation here is of a conservatory associated with an existing house. In any event, the conservatory will be *physically* attached, but that isn't the issue if you read the document. The discussion there is about *thermal* separation, which is not the same thing. .andy

To email, substitute .nospam with .gl

[Peter Crosland]

Yes but according to the local BCO it IS subject to building control UNLESS the installation is done by a FENESTA approved installer. Two installations locally since 1st April have gone through this and not without problems either. Are you saying that there was no legal basis for this?

[Andy Hall]

That's what the Statutory Instrument says and so does FENSA.

the ones that you mention not exempt because they didn't meet one or other of the requirements perhaps? Also, the applicable date seems to be April 2002.

.andy

To email, substitute .nospam with .gl

[Peter Crosland]

I must wake up! I of course meant FENSA. Yes I see what you are saying now. What it comes down to is that Chris did not give enough information to decide one way or the other. Certainly the local BCo people seem thoroughly confused about some of the detail. No doubt they have been dropped in the brown and malodorous. The April 2003 date of course refers to boilers which on of these schemes involved replacing and relocating that added to the confusion.