De Minimis (margin of error) help regarding new drawings & application.

[Ron_UK]

Hello.....again!

I'm currently preparing CAD drawings for application to build a single story extension.

My question is regarding the De Minimis or margin of error allowance when you come to build.

For example, on my drawings i'm making the extension 4 Metres wide, if i block on the lines the blocking width from one side to the other will be 4 Metres but if i then apply an outer render it will add 1.5cm to each side making it 3cm over to 4.03 Metres.

Would the extra 3cm fall under the De Minimis allowance?

The old existing extension (to be demolished) is 4 Metres wide at the base but 30cm up it is has been rendered making the extension above the 30cm line to be 4cm wider to 4.04 Metres. The original plans stated 4 Metres so wondering if he got away with it as the base bricking is spot on?

All good learning
Thanks in advance for any help / advice.
Ron

 

[Captain Nemesis]

Ha - Ive got a similar issue but where your extra is 3cm mine is 10 or so as its associated with applying EWI to the existing house.

 

[mrrusty]

I sent plans in for planning recently with "all dims are +/- 100mm" marked on. Never queried.

 

[Captain Nemesis]

 

[^woody^]

Drawings for what? Planning, building regulations or quotes? It makes a difference.

Anyhow, dimensions should be accurate there is no tolerance, and whatever is stated is what is built to and is what any permission is based on. No tolerance, although in practice some leeway is accepted.

When dimensioning walls, the dimension is to the masonry face whether external face or internal face. You would specify wall dimension and the render and plaster thicknesses annoted separately.

 

[Ron_UK]

Drawings for what? Planning, building regulations or quotes? It makes a difference.

Anyhow, dimensions should be accurate there is no tolerance, and whatever is stated is what is built to and is what any permission is based on. No tolerance, although in practice some leeway is accepted.

When dimensioning walls, the dimension is to the masonry face whether external face or internal face. You would specify wall dimension and the render and plaster thicknesses annoted separately.

Firstly planning permission drawings so not that technical then onto the technical drawings if / when approved.
Just planning ahead Woody.

I like MrRusty's reply, adding a +/- error.
Maybe i could do +/- 1%, that would give them pre-notice of 4cm deviation?

Thanks
Ron

 

[Ron_UK]

I sent plans in for planning recently with "all dims are +/- 100mm" marked on. Never queried.

Oh i dooooo like that!
Great idea but i'm not sure on 100mm deviation, lol.
I could go +/- 1% on the 4M wide build, that give me 4cm either way.
Thanks
Ron

 

[^woody^]

It don't matter if you put 1000% tolerance, it means jack.

The drawings must be accurate, both measured on site, annoted on plans and the extension drawn accurately relative to other features, that's planning law, no tolerance. But whether deviations matter to a basic extension in someone's back garden is another matter.

But it might matter if the extension is actually a caravan, as I am informed that "caravan dimensions matter" - and that is not a political movement but some obscure law, apparently.

 

[Ron_UK]

Ha - Ive got a similar issue but where your extra is 3cm mine is 10 or so as its associated with applying EWI to the existing house.

I think you'll be ok

It don't matter if you put 1000% tolerance, it means jack.

The drawings must be accurate, both measured on site, annoted on plans and the extension drawn accurately relative to other features, that's planning law, no tolerance. But whether deviations matter to a basic extension in someone's back garden is another matter.

But it might matter if the extension is actually a caravan, as I am informed that "caravan dimensions matter" - and that is not a political movement but some obscure law, apparently.

I guess at the end of the day the actual deviation allowance is totally at the discretion of the BCO when he or she checks it.
I'll make dimensions exact on the drawings, if they approve my chosen brick face then i can brick exactly to specs on plan.
The house is mostly rendered but trying to get away from it, fed up with painting every year .

Thanks for your input.
Ron

 

[frutbunn]

Accurate plans, that's a laugh, half the apps are building notices in any case. Half of the "plan drawers" don't do B Regs these days and most of the ones that do never look for a drain never mind lift up a cover to see where it goes or how deep it is, there's a few I deal with who knowingly show things differently to the actual site conditions to get them passed on paper, job starts, guess who ends up sorting it out on site and its not the plan drawer! Even chartered Architects, one "copied" the plans I'd drawn for a terraced house next door, but assumed the ridge was central. it was actually offset and had two different pitches front to back and the purlins were in different positions, staircase only worked on paper, he'd never even popped his head in the roof space. Ended up sorting that one out as well as it was a mate of mine doing the work!

 

[johnny2007]

Never seen a BC officer carrying a tape measure.
30mm?
100mm?
On landlord's instructions I built extensions 500mm over the plans and never had a come back.
100mm in building terms is nothing, unless you're going over the boundaries of course.

 

[^woody^]

I guess at the end of the day the actual deviation allowance is totally at the discretion of the BCO when he or she checks it.

Don't confuse dimensioning for planning and that for building control.

Planners don't do any site checks unless someone complains. Building control wont measure on site but if you dimension something incorrectly on the plans or build something incorrectly measured on site then if its a structural matter, it will either be rejected or you'll need to justify it via calculations.

And if your builder quotes for one dimension and finds its actually bigger on site, expect to pay more for materials and labour.

I really can't understand what's so difficult in actually doing it right. Non of this tolerance nonsense, just measure it and dimension it properly how hard can it be?

 

[DevilDamo]

@Ron_UK Assuming your render will not be taken down to ground level, will you have facing bricks for the first courses up to DPC level? If so, remember those courses end up having to accord to brick dimensions in order to save cutting and wastage on site.

Another example are brick plinths. The dimensions Planning are interested in is the main wall above the plinth. Your so called ‘Planning Architects’ seem to ignore this so when the Building Regulation/working drawings are produced, positions of walls are adjusted for access, fire separation, door openings, etc... One of the reasons I refuse to take on projects that have already secured Planning approval by others.

 

[Ron_UK]

Don't confuse dimensioning for planning and that for building control.

Planners don't do any site checks unless someone complains. Building control wont measure on site but if you dimension something incorrectly on the plans or build something incorrectly measured on site then if its a structural matter, it will either be rejected or you'll need to justify it via calculations.

And if your builder quotes for one dimension and finds its actually bigger on site, expect to pay more for materials and labour.

I really can't understand what's so difficult in actually doing it right. Non of this tolerance nonsense, just measure it and dimension it properly how hard can it be?

This is amazing, the planners don't do site checks and the BCO does not measure anything.....so who does?

@Ron_UK Assuming your render will not be taken down to ground level, will you have facing bricks for the first courses up to DPC level? If so, remember those courses end up having to accord to brick dimensions in order to save cutting and wastage on site.

Another example are brick plinths. The dimensions Planning are interested in is the main wall above the plinth. Your so called ‘Planning Architects’ seem to ignore this so when the Building Regulation/working drawings are produced, positions of walls are adjusted for access, fire separation, door openings, etc... One of the reasons I refuse to take on projects that have already secured Planning approval by others.

The original extension has brick face up to DPC, that measures 4 Metres spot on from left to right, then it's rendered above the DPC, this added 20mm each side, so at the bottom below DPC it's 4 Metres across and above DPC it's 4.04 Metres. The original plans state 4 Metres.

I'm doing all the new plans myself, i have a technical CAD background, plus bricklaying, woodworking, plumbing, electrical....but not plastering, i hate it!

 

[^woody^]

This is amazing, the planners don't do site checks and the BCO does not measure anything.....so who does?

No one does.

The process is reliant on the plans being accurate, on trust, and things are only re-measured if a complaint or issue arises.

But when used for construction, dimensions do matter and if the dimensions are wrong, unworkable and the builder moves things, then knock-on problems arise when other things don't fit, or calculations then no longer work.