Plans For An Extension

MrBump

I have a small (3x4 meter or so) knackered old conservatory on the back of my house, and Mrs Bump and I are considering getting a single story brick built and pitched roof extension in the same footprint.

We went slightly down this route a year or so ago, and got someone in to do some drawings.  He was next to useless and eventually stopped emailing me... he was cheap as shite though, so I guess you get what you pay for..?

Speaking of which - anyone know what to expect for some drawings for builders to work from?  I'm expecting this to go through permitted development.  I don't know how involved those plans should be... I did email a proper architect and got a stock response from him estimating around £1500 for plans.  That seems pretty expensive to me for what is effectively a brick built square on the end of my house.

RaymondLin

It depends on your local council, you might not even need planning permission if it is under a certain size, but you will need building regs.

Jimbro66

RaymondLin said:

It depends on your local council, you might not even need planning permission if it is under a certain size, but you will need building regs.

^^ This, and building regs drawings need to be quite detailed so are more work than drawings solely for planning permission. That amount of detail is also the minimum you’d need to get competitive quotations from independent builders. How much to pay? Well bear in mind that an architect does it for his full time living so will inevitably be dearer than someone that does this sort of work part-time from home. If there is no particular element of design required for your simple extension you are better served by an architectural technician whose costs will be lower than an archictect’s. There is, however, more than a little work in building regs drawings so don’t expect (as many seem to do) to get them for just a few hundred pounds.

RaymondLin

Typically planning permission is done in 1:100 scale, it's like an A4 piece of paper for a small extension.  just a Plan, location plan and 4 elevations.  It might not even need a cross-section.

For building reg you would need like a 1:50 or 1:20 scale drawing, 1:5 for things like windows opening or any specialised designed parts like the joints to the existing and foundation.

How difficult it is depends on a lot of things.  Any plumbing needs moving, like pipework, are there drainage outside that needs moving due to foundation, how does it join up the existing building.  The position of where it is will also need to following building reg not to block your neighbour as there is a thing call Right to Light.  

It's never as simple like "I want a square brick box at the end of my house added", one has to really at least visit your house to check all these criteria over.

sw67

I paid £1800 for detailed plans and structural engineer for a extension similar to yours. I could have went permitted development but went for certificate of lawfulness from the council so I don't have issues when selling. The detailed plans paid for themselves as I had a fixed price building quote rather than a estimate

MrBump

sw67 said:

I paid £1800 for detailed plans and structural engineer for a extension similar to yours. I could have went permitted development but went for certificate of lawfulness from the council so I don't have issues when selling. The detailed plans paid for themselves as I had a fixed price building quote rather than a estimate

Bloody hell, that's the first time I'd heard of a Lawful Development Certificate...  I think I need to do some more reading...

Fuengi

This is what I do for a living, but I'm not near you so I won't be doorstepping for work!

My typical charges for survey / design / planning / building control drawing are £2500 - £3000 depending on complexity, plus you'll pay a structural engineer and planing and building control fees. 

For that you'll get laser measured survey and drawing of the house as existing, several different layout options, elevation options, planning and building control drawings. Expect to pay £4k in fees before you start. It's a lot of work.

The design work you put in pays back in the build and the final result. Personally, I never understand why anyone would take a short cut on work to their own house - usually the single biggest asset any of us own. Expecting builders to construct from no plans or from inferior drawings is asking for trouble.

Even if you think it falls under permitted development CHECK with your local authority. You can either do a Lawful Development Certificate, or most authorities will respond in writing to sketch drawings confirming the proposals fall within your PD rights for a small fee. Get it in writing. 

If you decide to employ an architect / draftsman have them submit the relevant drawings to the local authority. 

boogieman

We did basically the same as the OP a couple of years back. The builder recommended a planning guy, who we ended up using. He was really slow (except when it came to cashing our cheques) but it only cost us about £1000, including all the drawings, calculations for RSJ sizes etc and submission to the council on our behalf. I guess you get what you pay for. 

MrBump

Thanks all - there's some useful stuff in there.

@Fuengi - it's not really a case of taking shortcuts, it's not having any experience in this industry and being wary of being taken for a ride... Someone could tell me that I can expect to pay £100, and someone that I should factor in £10000 - how would I ever know?

CHrisP86

We are doing exactly this right now (builders in the garden digging foundations as I type).

If you don’t need anything complex, find a decent structural engineer who can do planning and building reg drawings for you. Ours cost around £1,100, including submitting to the council and getting the building regs approval for us. 

I think we are within permitted development on ours but we had to apply for a lawful development certificate anyway (might be different where you live).

Building control fees are around £500, including site inspection.

Fuengi

MrBump said:

Thanks all - there's some useful stuff in there.

@Fuengi - it's not really a case of taking shortcuts, it's not having any experience in this industry and being wary of being taken for a ride... Someone could tell me that I can expect to pay £100, and someone that I should factor in £10000 - how would I ever know?

There are a range of services and associated fees, of course. To put things in context I generally work on properties of £400k to £800k. I've yet to hear anyone complain that good design has negatively impacted their enjoyment of their home.

However, in ten years of running my own practice I've lost count of the number of times I have been called in to pick up the pieces on a job after a poor initial design. 

By analogy, I've got two guitar pedals which were made by a local tech / builder. The cost of two of these are about the same as a Thorpy pedal. Neither work particularly well and they are worthless 2nd hand. Probably should have bought a Thorpy pedal! 

viz

I just do it myself in powerpoint, fill in all the paperwork, then got planning permission, and I use a local building consultancy for the building regs. 

ToneControl

I got French windows put in (I need planning permission for that)
The major local window company knew how to do it, and the RSJ to use, but I needed a plan of the rooms affected
I gave up trying to find someone affordable, and did it myself on graph paper with a scale ruler
The council accepted it and approved

RaymondLin

Planning is easy, I’ve seen it drawn free hand on scruffy bits of paper.  All the planners want to see is what it will look like, it’s doesnt need to be too technical.  If it’s to scale then you are 9/10th of the way there.

Drawing building reg drawings however is a whole other kettle of fish.  I went got an architecture degree and they don’t even teach you how to draw building reg drawings. I basically learned it during my year out between my RIBA part 1 & 2. 

King85

The drawings for my kitchen extension were £480 iirc with the beam calculations. Architect was excellent and made several changes at no extra cost. You don't have to post through the roof especially if it's something simple.

TTony

We’ve just had a £30k garage conversion done.

IIRC, plans were about £300.

Which is way cheaper than you’d normally expect because the builder knew the architect and we were happy that we’d work things out with the builder as we went along.  It could have been disastrous, but we knew and completely trusted the builder.

If we’d not had that situation, we’d have spent a lot more on the plans, because that’s really the basis of the “contract” that you have with the builder.  The plans should set out, clearly and in detail, what you want the builder to do.  If there’s any vagueness in the plans, the builder will have to interpret them, and builds X when you wanted Y.  There’s a huge amount in the detail that can make the difference between something that really works for you, and something that’s worse that what you’ve got now.

Iamnobody

As you have no experience then I’d get the plans done professionally including your regs and material specification so you get appropatiate and comparable quotes from builders.

Also if you want a particular brand/style of tile or insulation - whatever, make sure it’s specced or else your builder will quote for the very basic spec needed to throw the thing up. 

Try not to get generic statements on the drawing like ‘or equivalent’ or ‘to client spec’. A cheap insulation board might have the same thermal properties as top brands but costs a third of the price etc.

Get a reccomended builder if you can. 

We had a two story extension done in 2017 and lived through the build with two young kids. I’m not sure I’ve fully recovered from the stress yet!

Dominic

You don't need Building Regs drawings.........that's 20 years out of date for a small domestic project
Instead you serve Building Notice and appoint a private surveyor who is qualified to sign off the works
You would be best doing a package deal from cradle to grave for the whole lot ......and he should do a design spec for the builders 
 If there are any structural support elements you will need engineers prescription and calcs for proving of any beams etc

jonnyburgo

Chances are that a good builder will know a decent architect, ours did and he came in about £2500 for a big extension single story back and side of house extending 4 metres from back of house and 2 from side.

lovestrat74

I did mine a few years ago when the permitted development regs were doubled - one of Cameron's better ideas to get people spending/building again - so we went out 6m. 

We had a clear design in our head (drew up several plans over a long period and finally agreed on what we wanted) and got a structural engineer to do the calcs and the building drawings to get it approved by local authority. Couldn't justify the additional cost of an architect as we were not looking for ideas and a design as we had done this ourselves.

Get a good builder, one that is either known to you personally that you can trust or one that comes recommended and work can be verified.

Keep on top of it and make sure you get what you want because all trades are well known to a) blame the last trade that was in before them if they 'say' they cannot do it the way you want, or that it won't work like that because chippy/brickie/sparkle etc didn't do x,y,a. And b) take the easiest route not necessary the actual path to completing their job.

Even though at times it was painful ours was well worth it! Good luck  

RaymondLin

lovestrat74 said:

I did mine a few years ago when the permitted development regs were doubled - one of Cameron's better ideas to get people spending/building again - so we went out 6m. 

We had a clear design in our head (drew up several plans over a long period and finally agreed on what we wanted) and got a structural engineer to do the calcs and the building drawings to get it approved by local authority. Couldn't justify the additional cost of an architect as we were not looking for ideas and a design as we had done this ourselves.

Get a good builder, one that is either known to you personally that you can trust or one that comes recommended and work can be verified.

Keep on top of it and make sure you get what you want because all trades are well known to a) blame the last trade that was in before them if they 'say' they cannot do it the way you want, or that it won't work like that because chippy/brickie/sparkle etc didn't do x,y,a. And b) take the easiest route not necessary the actual path to completing their job.

Even though at times it was painful ours was well worth it! Good luck  

Essentially, you got to be a good project manager as you are it!