Any architects out there?

teneighty

Building Regulations drawings for a single storey residential extension costing £1200 I would expect to see 2 or 3 A1 size plans showing all elevations, existing and proposed at a scale of 1:50 for proposed and 1:100 for existing. I would also expect to see detailed floor plans, proposed and existing at 1:50 with all the necessary construction and building regulation notes including all details for the roof structure and covering, wall construction including insulation and lintels etc. floor construction, pretty much everything you would need to build it except internal finishes, decoration schedule, electrical layout etc. I would also expect to see at least 1 section through the extension at 1:20 preferably or 1:50 to show further construction details. (Things are different in Scotland where I understand a structural engineer will certify all the structural elements but thankfully that does not apply in England)

These plans are usually what you would need to get builders quotes and what the vast majority of clients for this type of small project would use. You would only have detailed construction drawings and specification if the designer was providing a full contract administration/project management service or you wanted the full belt and braces approach to get very accurate detailed quotations or it was a more complex project.

That is what I would provide anyway. If you Google "Building Regulations Plans" there are countless examples of the sort of thing in images.

By the way I do not know where this idea that all buildings on clay sub-soil need piled foundations came from. Half of the south east of England sits on clay and piled foundations are NOT usually needed. You would usually pile if you had bad ground at the surface like peat or soft wet sand but good solid ground like clay deeper down. The piles go through the bad ground until they sit in the good solid clay or similar layer deeper down.

Furts

OP clealy has the hump with me. That is why I was "out" much earlier. I did chip in there after so more fool me But here goes again.

Much like teneighty and Kiran I agree regarding clay and piles. I have personally been involved with building thousands of new homes - physically working on them. Dealing with the technicalities, taking these and implementing them. I know ground conditions and much else.. Put on the spot I cannot recall one home where clay required piling. One challenging clay site incurred additional ground work costs - a lot - but piles were still not required.

I suggest OP chews over these observations.

OP has asked where they went wrong. The answer here is as obvious as the nose on my face. Between OP and the "friend" who was deemed "designer" was joint total incompetence. Quite likely the "friend " has shafted OP . Only OP knows why and how here. Regardless, had a competent professional been properly engaged from day one, and OP engaged with this person, then everything would have been plain sailing.

By OP quoting the friend doing sketches, and the other friend having a conservatory built shows how little OP knows about construction. The old saying is a little knowledge can be dangerous. This has applied to OP. But also these two examples from OP illustrate perfectly why OP should not have been going about matters as they were, and possibly still are.

EachPenny

Beenie wrote: »

Our current house is not piled. However, the new build will be sitting on metres of clay, and we cannot have an extension built that will move independently of the main house. Hence the piling. This area is full of piling companies; it's very common as I said earlier.

The metres of clay is largely irrelevant, it is only the uppermost level where there might be changes in moisture content which would be of concern. However many tens of metres there are below that level will have no impact on movement at ground level.

The bit in bold above goes to the heart of the issues other posters are mentioning about piling. The logic you've used is wrong. Having piled foundations for an extension with (say) strip foundations for the original house is an excellent way of virtually ensuring the house and extension move independently of each other. The house is effectively 'floating' on a sea of clay, whereas the extension would be firmly anchored to the sea bed.

In an ideal world you'd look to match the foundation type of the extension to the type used for the original house, subject to there being no evidence of problems with differential movement.

Unfortunately in some parts of the country piling is seen as the only option to dealing with clay soils. In part that may be because the depth of foundations BCO's require result in very deep excavation, creating large quantities of spoil to be disposed of, plus large quantities of concrete to fill the holes back in. Piling becomes economic where the cost of bringing in the plant is less than the spoil disposal/material costs involved in deep conventional foundations.

The economics often work in the favour of piling when you are building several whole houses and there is enough work to keep a piling rig busy for a few days. I raise an eyebrow at the notion that piling the foundations of a single storey extension could generate the same economic advantages.

If you'd already had input from a BCO then I'd understand if the choice of piling was driven by a very strong indication from the BCO that nothing else would be acceptable. But I'm not sensing that is the case from what you've previously posted.

teneighty

I wonder if they have some large trees in close proximity to the extension and it is that causing the issue with piling rather than lovely firm clay.

Beenie

sloping site, trees, conservation area.....all these problems.

This photo is the closest style to that of my house. Excavated into a hill side, and garden (where the extension will be built) is above ground level.

https://www.homebuilding.co.uk/foundations-for-difficult-sites/

EachPenny

Beenie wrote: »

sloping site, trees, conservation area.....all these problems.

This photo is the closest style to that of my house. Excavated into a hill side, and garden (where the extension will be built) is above ground level.

That small detail makes the issue of roof material far more important. If you want to deviate from the approved plan you will almost certainly need to go back to the planning authority and get consent to alter the materials you previously specified. The builder(s) who suggested you just switched because it couldn't be seen should not be relied on for advice on any other subject.

If your project is as complex as the house in that picture then you will need a structural engineer involved without doubt.

Beenie

The structural engineer has already done the calcs and provided drawings of the piling, the lintels and the roof rafters. That was two months ago. He was instructed from the word go as all the builders said such plans would be necessary. Because the architect in his contract says he will liaise with structural engineer/BR inspr, we assumed that he would incorporate the SE's drawings into his drawings (the ones I thought we were getting for our money, but seem to have misunderstood the process -- and he did nothing to clarify matters).

The PP drawings show zinc raised roof, and that is probably what we will go with anyway.

System

The usual process would be to have the Architect involved in the design as well as the building control drawings, sounds like it's a reasonably technical excercise here in a conservation area, changing consultants halfway through is definitely not the money saving way as now someone has to do the technical excercise on a set of drawings which can't change much...

EachPenny

Beenie wrote: »

The structural engineer has already done the calcs and provided drawings of the piling, the lintels and the roof rafters. That was two months ago. He was instructed from the word go as all the builders said such plans would be necessary. Because the architect in his contract says he will liaise with structural engineer/BR inspr, we assumed that he would incorporate the SE's drawings into his drawings (the ones I thought we were getting for our money, but seem to have misunderstood the process -- and he did nothing to clarify matters).

So are you saying the structural engineer has already designed the roof then? I thought this was what you were expecting the architect to do?

I think the builders have confused matters. the normal approach would be to obtain structural design calculations/plans (if necessary), but only once the architect has developed the design in the way the client wants.

It sounds like you are asking your architect to draw up a design based on the structural engineer's work - which to be frank leaves little for them to do other than to annotate the structural engineer's plan (or attach to it) the details that would be required by the BCO.

I'm confused... and I can imagine how your architect feels.

Newuser1987

I am not too sure what it is you are expecting the architect to do in addition to what he has done. The roof rafters have been designed by the engineer as they should.

It seems more like you personally want to know how and where every nut and bolt is going. You wont get this and dont need it. I really dont understand what you mean by the roof needs designing?
The engineer has told you the roof rafter sizes
The material finish is what it is and installed as per manufacturers recommendation
I then imagine the architect has put what insulation is required in his notes
You have elevation drawings from the planning drawings.

What more do you want or need? When I do BR drawings (I'm an architect) I dont change the elevation drawings from planning. I do provide a cross section of the building in a bit of detail but I probably wouldn't go into that detail for something simple like this.

What you should now do is ask the architect to submit the drawings under a full plans application to your local authority and wait to see what conditions they come back with. If none then clearly your architect has done his job. If they come back with conditions then give him a chance to respond to them.

I think you need to be clearer on what you actually want. More importantly ask your builder what exactly they want to be able to give you a robust price.