Accuracy of Building Control drawings?

[Codydog]

Hi all, I'm building a small 1.5 storey side extension on our house, dining room downstairs and bedroom upstairs. Just a bit of advice please.

 

I've had various issues with the Building control plans/Working drawings, the original inaccuracy I noticed was that the front to back measurement was 200mm out, meaning that the beams for the floor were too short.  I contacted the architect and told him about the difference and that I was concerned how this might effect the structural calculations for the pitched roof etc.  He told me that I should have ordered the beams from site measurements rather than from the plan measurement, which I suppose is fair enough. It only cost me an extra day and £60 for a couple of additional beams, so no great worry about the block and beam floor. (the measurement was a printed measurement, and not scaled from the plans)

 

I'm now at the stage where I'm above 1st floor joist height with the brickwork and am trying to mark out what course the wallplates will be on (different heights front and back), I've noticed that the plans and the Structural Engineers calculations show a 45 degree roof,  the existing roof is 50 degrees, so for the extension roof to run parallel it also needs to be 50 degrees.  

 

Surely the plans should be more accurate? Do the structural Engineer's calculations need adjusted?  Do I just make it up as I go along and hope it looks similar to what was approved by planning?  We have a dormer on the plans at the front, but I'm now wondering if the roof line will be above the window meaning no dormer required, but not what was granted by planning and passed by building control.

 

Thanks!

[Olf]

To start with, planners aren't bothered if it can be build or if it colapses the moment scaffolding goes down, as long as it looks nice from local planning perspective. BC on the other hand could not care less how ugly it is, as long as ticks all the required boxes of building regs. Of course it makes sense for the design to be decent enough to be used for both and be stuck to, but clearly it is not the case here.

With the planning do check what exact conditions were stipulated: it may be pitch of the roof, but it might be max height only - either as a dimension or in reference to the existing building, that may or may not give a bit of flexibility. SE calculations are based on the plans he got, so if they showed 45', he would use that value for the calcs.

Ultimately it is a blame game: BC is happy to accept stock solution, anything custom (like your roof) and you pay SE to do calcs and put it on his policy. Ultimately should anything went wrong, it is you being affected - and can get out with less of a problem if you can prove wrongdoing of SE or BC. So if you're happy to change the pitch so be it, but the 1st thing anything went wrong, the SE would wash his hands away (and so BC).

It feels like the architect is a bit light on sticking to detail, maybe check the initial spec of the drawings  - if he ignored the need to follow the pitch of the original house, surely he needs to do something about fixing it. At the end of the day he took money, so the blame game ball lands on his half.

[ETC]

Sounds like a bit of a sloppy measured survey if you ask me - if that’s what your agent was paid to do. If not and he was given dimensions by a third party or was for some reason or another using photographs (it happens) then the blame shouldn’t really lie with him/her. On the other hand - and in my opinion - if he/she was paid to do a measured survey then the drawings should have been accurate irrespective of whether or not the beams were to be measured from site dimensions or the drawings. If I was told my survey was 200mm out I’d be gobsmacked not to say very embarrassed.

 

Going forward you should ask you agent to double check his survey and to amend his/her drawings and those of any consultants that have used the measured survey to design parts if the structure. If that is if you paid for a measured survey.

[markc]

BC drawings are rarely accurate and are intended to give an idea of dimensions, materials and construction methods. 
an accurate building survey is rarely worth the cost leaving most dimensions to be confirmed on site … heights, levels and length of beams etc. Once the existing building/founds etc. Are opened up.

[Temp]

Building Control drawings are intended to satisfy Building Control that the end result will meet the Building Regulations. Architects will happily sell you a set of Construction Drawings that tell the builder what to build. They may contain more details not required by Building Control. 

[saveasteading]

Just now, markc said:

BC drawings are rarely accurate

 

Do you mean deliberately vague or plain wrong?

I'm surprised to hear that as my view has always been to present drawings to the BCO that we could build from. If you don't know the dimensions  you can't design/order/ build/properly.

 

Once worked with (against) an Architect who was keen to offload as design and build, and promptly deleted all the dimensions from his drawings. That was for the best as it happens, but the attitude  shocked me.

 

So thanks, I will bear that in mind in these discussions in future.

3 hours ago, Codydog said:

measurement was 200mm out,

Re this post: the beams were too short, meaning that they now span further than intended?  Ditto the roof structure.

Increasing a span can be a significant change as the strength is not a linear change but related to the square of the span.

May well be ok but do get it checked by SE.

[saveasteading]

2 minutes ago, Temp said:

Architects will happily sell you a set of Construction Drawings

Good point. I forget how little input some architects are engaged to do.

So if paid for planning only then he is right that it is not down to him.

[ETC]

“BC drawings are rarely accurate and are intended to give an idea of dimensions, materials and construction methods. 
an accurate building survey is rarely worth the cost leaving most dimensions to be confirmed on site … heights, levels and length of beams etc. Once the existing building/founds etc. Are opened up.”

 

Absolute rubbish! I wouldn’t want your drawings if they’re not accurate. As I said - a sloppy measured survey.

 

“Building Control drawings are intended to satisfy Building Control that the end result will meet the Building Regulations.”

 

Correct.

 

“Architects will happily sell you a set of Construction Drawings that tell the builder what to build.”

 

How else would the builder know what to build?

 

“They may contain more details not required by Building Control.”

 

This rarely happens - in fact drawings more often contain little or no useful or confusing construction information.

Edited September 28, 2021 by ETC

[saveasteading]

11 hours ago, ETC said:

How else would the builder know what to build?

 

In a great deal of situations, the tradesperson knows better how to do it.

Specialist builders know a great deal about their type of work, whereas Architects will agree to design anything (I mean that, as I am unaware of an Architect ever declining a commission due to lack of experience.

Also I have met many an Architect who isn't too great with numbers.

 

So it depends on skill levels, and there are plenty of Architects who have these abilities.

 

On the other hand, I know a very skilled and conscientious Architect who is often only instructed to obtain planning permission, and is then paid off.

The builder and developer together then alter layouts and details to suite the marketplace, leaving the Architect none the wiser.

 

BUT it must be made clear what is expected,  we don't know the exact situation here, but it should e the expert, ie the architect, who makes it clear to the client what they are getting and not getting.

12 hours ago, ETC said:

drawings more often contain little or no useful or confusing construction information

So how does the builder know what to build?  Full circle.

[the_r_sole]

No matter the scenario, planning drawings, building regs drawings etc are not construction drawings - there may be enough information on them for a builder to take on to construction but that's not the purpose of those drawings.

With any set of drawings they should however be as accurate as possible, but with existing buildings it's absolutely critical for a contractor to do a dimension check as they start to open things up.

There should be notes on any drawings stating the purpose of the drawing and advising that all dimensions are site checked - no one would ever pay us to go and re-survey a property once it's been opened up and redo all the drawings, it has to be a coordinated effort to report any differences between the assumptions made at the initial survey and the reality on site (although 200mm is quite some way out!!)

[saveasteading]

39 minutes ago, the_r_sole said:

There should be notes on any drawings stating the purpose of the drawing

As  most self-builders are genuine amateurs, it behoves the professionals to make it very clear what they are doing or not. This may not always be to the liking of the client, and they may not appreciate that they will soon be 'on their own' unless they pay more. They may not be 'listening'.

 

The unhappy clients on this blog seem usually to be of considerate disposition. I wonder how badly the others get on.

[ETC]

“In a great deal of situations, the tradesperson knows better how to do it.”

 

Lol. I’ve met plenty of “tradespersons” that I wouldn’t trust to sit the right way on a toilet never mind build something properly. Yes there are good contractors out there but very few I would trust to build something without proper drawings. Most contractors I meet wouldn’t know what the Building Regulation requirements are with a “we’ve always done it this way” attitude.
 

“Specialist builders know a great deal about their type of work, whereas Architects will agree to design anything (I mean that, as I am unaware of an Architect ever declining a commission due to lack of experience.”

 

That’s a very cynical out look - are you sure you’re talking about registered architects and not the plan drawer who’ll knock anything up for a few hundred quid irrespective of experience.

 

“Also I have met many an Architect who isn't too great with numbers.”

Especially when it comes to fees. Most people would rather spend a few grand on a new tv than pay their architect a decent fee. And I’m talking about an architect not your pseudo “architectural designer”.

 

 

“No matter the scenario, planning drawings, building regs drawings etc are not construction drawings - there may be enough information on them for a builder to take on to construction but that's not the purpose of those drawings.”

 

I disagree. Building Regulations drawings should have enough information on them to at least build the shell. It may not itemise sanitary ware, finishes or other PC/Provisional items - and perhaps foundations where trial holes have not been excavated - but there should be enough information on the drawings to build from. I wouldn’t accept planning drawings as a BC submission - they’d be sent straight back to the agent.

 

“With any set of drawings they should however be as accurate as possible, but with existing buildings it's absolutely critical for a contractor to do a dimension check as they start to open things up.”

 

I agree completely but getting the contractor to do a dimension check doesn’t excuse a sloppy measured survey - especially one that it 200mm out on a single dimension.

 

“There should be notes on any drawings stating the purpose of the drawing and advising that all dimensions are site checked - no one would ever pay us to go and re-survey a property once it's been opened up and redo all the drawings, it has to be a coordinated effort to report any differences between the assumptions made at the initial survey and the reality on site (although 200mm is quite some way out!!).”

 

if I was paying you to do a measured survey I would expect it to be accurate the first time around - and if it wasn’t and a mistake had been made I’d expect you to redo the survey and any consultant’s drawings that were affected by the error free of charge.

 

“As most self-builders are genuine amateurs, it behoves the professionals to make it very clear what they are doing or not.”

 

Absolutely - and make sure it’s in writing for both parties to agree to and sign.

 

“This may not always be to the liking of the client, and they may not appreciate that they will soon be 'on their own' unless they pay more. They may not be 'listening'.”

 

That’s why it’s critical to put everything in writing and for both parties to agree the extent of the service and the fee to be paid.

 

My honest opinion is that any architect worth his salt will or should provide any client with accurate drawings and should clearly set out the terms of his or her appointment. If that means just doing the planning or just the building control drawings then so be it.

 

Thank you for reading.

 

ETC.

 

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[the_r_sole]

50 minutes ago, ETC said:

I disagree. Building Regulations drawings should have enough information on them to at least build the shell

 

Why should they?

The drawings should have all of the relevant information to show compliance with the building regulations, that's it - yes you might be able to use them to get all the building components and build from, but that's not the purpose of the drawing 

53 minutes ago, ETC said:

if I was paying you to do a measured survey I would expect it to be accurate the first time around - and if it wasn’t and a mistake had been made I’d expect you to redo the survey and any consultant’s drawings that were affected by the error free of charge.

 

My survey drawings would be as accurate as possible on site, but I'd be making loads of assumptions as to what wall build ups are, where floor levels might run through from room to room, how plumb walls are etc - once a building has started to be opened up you get more information so you shouldn't expect that the new state of the building is exactly as was measured when it was in a different state - if you had someone who could do a 100% accurate xray survey at the start of project before any design had been done, they'd be worth a fortune!

We've even had point cloud surveys done which are mm perfect on projects and you still have to make assumptions on the bits you can't see!

 

If your expectation is that nothing changes from drawings to site work and you can assume all the drawings are mm perfect, you end up in a scenario like the op - building work, especially extensions, isn't an exact science, there are too many variables for nothing to change from the start to the end of a project, if you understand and accept that you'll get a much better result at the end of the process

[ETC]

I think this is a debate where we are going to agree to disagree.

 

If drawings prepared for a Building Control submission aren’t capable of being built from - what is their purpose?. A good set of Building Control submission drawings should be capable of being built from. They may not be Tender Drawings but should be able to be built from. As I said, they may not list finishes, sanitary ware, ironmongery or PC or Provisional Sum items - although many commercial submissions will do where there is a requirement for the submission to comply with facilities for the disabled and visual contrast but they should be detailed enough to build from.

 

I agree that the accuracy of a survey may depend on the type of building to be surveyed and how much of the existing structure and construction is visible - if this was a large listed type building or structure it might not be possible to determine the make-up of all elements of the structure and construction - but that’s not being debated.

 

However, it should be totally possible to locate walls, floors and roofs in relation to each other even when they are not in the same plane. I do agree that things can change when a building is opened up but the overall dimensions measured shouldn’t change from the survey to the start on site - unless of course the survey was inaccurate to start with or the elves were in over the holidays and started moving walls and floors around - sorry for being facetious.

 

In my experience inaccurate measured survey drawings and the knock-on effect for other disciplines can cause additional unwarranted and unnecessary cost implications for a project, can make professionals look incompetent and can incur the wrath of clients.

 

I’m not getting at anyone and yes we don’t know the situation of this particular project but I do expect a measured survey - at least for a small domestic project - to be accurate.

 

Thanks.

 

 

[saveasteading]

2 hours ago, ETC said:

are you sure you’re talking about registered architects

 

I am afraid so. I used a capital A consciously.

If you are one, then the thing is that you don't work with the others.

 

I was careful with my wording and stated 'specialist contractor' by which I also imply some standing.

 

2 hours ago, ETC said:

I am unaware of an Architect ever declining a commission due to lack of experience.”

 

Anyone disagreeing with that? I speak from experience of some Architects having a go at anything, and some very serious errors needing to be sorted. I mean basic physics, keeping the weather out, building reg's and design principles for the function. Designing to a budget is another matter for another day.

But good and less good, a or A...do they ever say 'no, it is not something I am familiar with'?

 

20 minutes ago, ETC said:

 

I’m not getting at anyone

Nor am I. An interesting discussion though, from which I learn that there are very different experiences.

 

 

2 hours ago, ETC said:

Thank you for reading.

Thank you for writing.

[the_r_sole]

17 minutes ago, ETC said:

If drawings prepared for a Building Control submission aren’t capable of being built from - what is their purpose?

 

To show compliance with the building regulations, in a similar way that planning drawings show the information relevant to planning, building regulation drawings show information pertinent to building regulations - there is no other purpose for building regulation drawings. 

 

Construction drawings are used for construction - the name gives it away...

 

There might be information which can be extrapolated from any set for construction purposes, but that isn't the intent of the drawing

21 minutes ago, ETC said:

I’m not getting at anyone and yes we don’t know the situation of this particular project but I do expect a measured survey - at least for a small domestic project - to be accurate.

 

The point is, it can only be accurate at the time of the survey.

Believe me when I say, lots of clients don't even want to pay for a single day to do a survey and draw it up.

 

We have also seen times where we've done a survey for say a ground floor extension and only done a basic layout of the upper floor as it's not within the scope of our project, later the client will ask to make alterations on that level and not understand why we are saying we need to do a more detailed survey of the area...

[ETC]

Great debate.

 

I suppose we all have some valid points to make.

 

In my professional life I have seen some very, very good Building Control applications that can be built from and some very, very bad applications which are that terrible that a contractor would never in a month of Sundays be able to mark out from never mind build from even though the application may comply with the Building Regulations.

 

My question about what BC drawings are for was rhetorical - I know that they are to show compliance with the Building Regulations but there are varying degrees of BC submissions. Some are good. Most are not. However, in my experience the good BC drawings can be built from.

 

Just as a matter of interest what is the difference between your BC application drawings and your construction drawings. I’d be interested to know what additional information you provide that wouldn’t have some reference or relationship with and to the Building Regulations.

 

It’s unfortunate that you have experienced clients who wouldn’t pay for a measured survey. I’m afraid I wouldn’t be happy going forward with a project without one.

 

As I said before I’m not getting at anyone - we all have different experiences in our professional lives - different experiences of interacting with consultants, clients and the statutory agencies.

 

Thank you.

[the_r_sole]

13 minutes ago, ETC said:

Just as a matter of interest what is the difference between your BC application drawings and your construction drawings. I’d be interested to know what additional information you provide that wouldn’t have some reference or relationship with and to the Building Regulations.

 

Our building regulation drawings will state the relevant regulations in the spec whereas the construction drawings will have specific products specified,

building reg dims are generally internal room dims, construction are to structure,

loads more details added for construction stage

Sections for building regs will show a typical wall, we'd add more specific section details for construction

Window/door details for construction would be updated for specific manufacturers once they've been selected

detailed finish layouts, setting out etc internal elevations

we have a lot of energy calcs to go with building regs drawings usually due to people wanting loads of glass, so that needs to go with the regs but there's zero point in showing that to a contractor.

 

you could add all that to a building regs pack (sometimes when we're working with a self builder we'll do a building regs + set which gives a lot of that detail) 

but in our experience a building control officer only wants to see compliance, if you swamp them with information you make their job harder - clearly everything needs to comply with the regs but there's a point of "reasonable enquiry" to illustrate compliance.

 

Different drawings for different purposes - when a planning drawing shows a timber clad wall, you wouldn't expect it to tell you the fixing details for it - it's an iterative process where you add more and more detail as you go - we recently did an application over in Ireland where the building regs set was 6 sheets and the tender set which then went on to construction was 38!

[saveasteading]

I think there is a big difference between small domestic and anything else. The former is to the regulations document, quite detailed for England, and to generally accepted practices.

Anything bigger needs special details.

My career has been heavy civils and  commercial building construction, and the full drawings went to the inspector, with the absence only of setting out (ie where on the site) and externals.

With a growing relationship with the same independent inspector, we came to know what he didn't need or want to see.

 

On this hub we are mostly doing small domestic of course.

 

Any answers to 'do any Architects ever turn down a commission?'

 

[the_r_sole]

1 hour ago, saveasteading said:

 

Any answers to 'do any Architects ever turn down a commission?'

 

 

We do, on a daily basis!

If we can't add any value and our skills aren't needed or suitable we pass work on to others who might be a better fit 

[saveasteading]

Hooray. you are my first, although I won't count if you mean that it was too small.

 

But would you turn down something because you hadn't done one, and you might not know all there is to know?

My bugbear was sports halls. So many badly designed buildings, as if nobody had ever done one before.

Not knowing how much they don't know.

 

Actually it was good for business when the architect had done ignorant or  expensive designs because we could sort it, 

 

But it shouldn't be necessary.

[the_r_sole]

9 hours ago, saveasteading said:

But would you turn down something because you hadn't done one, and you might not know all there is to know?

 

Tbh most of the time it's nothing to do with the actual project type, we've done a lot of building types over the years and have some very experienced staff but a lot of the time we try to look at whether it's actually worth doing, whether we can do it, and whether doing it is right for the business - being all things to all people isn't a good business strategy imo

[Ferdinand]

On 28/09/2021 at 22:22, saveasteading said:

 

Do you mean deliberately vague or plain wrong?

I'm surprised to hear that as my view has always been to present drawings to the BCO that we could build from. If you don't know the dimensions  you can't design/order/ build/properly.

 

Once worked with (against) an Architect who was keen to offload as design and build, and promptly deleted all the dimensions from his drawings. That was for the best as it happens, but the attitude  shocked me.

 

So thanks, I will bear that in mind in these discussions in future.

Re this post: the beams were too short, meaning that they now span further than intended?  Ditto the roof structure.

Increasing a span can be a significant change as the strength is not a linear change but related to the square of the span.

May well be ok but do get it checked by SE.

 

@Codydog

 

I hope it is still the size you told Planning it was going to be ?

[Codydog]

I've plotted out the roof line and it misses the top of the window where we were meant to have  a dormer.  I prefer to have a full height ceiling and no dormer, but it's not what we have planning for.

 

I'm confused about what should I have asked the architects for? We paid for a measured survey, then design and plans for planning permission, then Building control drawings, then structural calculations and drawings. 

 

 

[Dave Jones]

any drawing that has to be scaled from using a ruler is a joke.

 

Construction drawings with every single measurement on them are mandatory. Once the builder has these he can then turn them into something close that can be built.