ChrisGamlin
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| posted on 1/5/06 at 07:58 PM |
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Planning / building an extension
We're in the first stages of looking into having an extension built on the side of the house, to build on a large single garage ( ), plus a
small utility room and downstairs loo.
Ive done some sketches and a bit of Photoshopping of existing house pictures to show the local planning office at a preliminary informal meeting, and
they say there's no reason fundamentally why we wouldnt get permission, so now we're into the stage of submitting actual plans etc.
During the meeting Im sure the woman said we wouldnt need to apply for building regs and wouldnt need to submit full architectural plans so I was
thinking I could exercise my Autocad skills or buy a bit of home planning software and rustle up some outline plans, but everything Ive read online
since, and even what it says in the application pack she gave us seems to suggest otherwise, that we're going to need full plans and also
probably go through building regs? If so, all this is obviously outside my skillset so we'd need to emply an architect 
Also, I know its a "how long is a piece of string" type scenario, but assuming we need to employ an architect, how quickly could we
reasonably expect to get through the enture process and be in a position to build? I know it takes ~8 weeks for planning applications to be processed,
so assuming we dont need to make any significant changes, is a late summer build an unrealistic target?
cheers
Chris
[Edited on 1/5/06 by ChrisGamlin]
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Guinness
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| posted on 1/5/06 at 08:20 PM |
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Chris
A late summer start on site will be more dependant on getting a decent builder who can do it, than the legal side. Start canvassing friends,
neighbours etc and get recommendations / numbers now.
Planning applications can be decided on amateur drawings, photos and written applications. Sometimes dependant on the size of the extension you
don't even need permission, but this one probably will, judging by your description.
For the building regs side of things, I'm certain you will need to make an application. 4-6 weeks is normal for a local authority to approve
drawings, but you can use approved private inspectors now. They can approve much quicker, but have a minimum charge that is much higher than a local
authority. I can get a £40k scheme approved for £500 plus the VAT, but it only takes days instead of weeks. Good if you need to be on site in a
hurry!
You'll need some form of technical advice to get to building regs application stage, but not necessarily an architect. They'll usually
charge you a fixed percentage fee based on the total build cost of the project. 7-10% of a £30k build soon mounts up. An architectural technician or
architectural services company might just charge you a flat fee for doing the drawings. Things you'll need to prove to the building inspector
are usually calculation based. Joist size, foundation depth, insulation values, roof pitch, drainage size / falls. These aren't too difficult
and don't take long to do. Fancy detailing stuff is where architects spend their time and make their money. If you just want a plain extension
save your money and just go plans based.
However, it depends on your experience in buildings. If you employ an architect, he'll probably act as a project manager too (for an additional
fee). If you haven't had anything built before it might be worthwhile. He can keep an eye on the builder and make sure that the right
materials are being used / quality is being acheived.
HTH
Mike
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albertz
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| posted on 1/5/06 at 08:36 PM |
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I'll second what Guinness says. A very informative reply. I regularly do plans for extensions and new builds and would definetly advise that you
find someone in your area that can prepare plans on a 'homer' type basis. Have a look at recent extensions in your area and try and find
out who did the plans, that way you'll maybe get a recommendation about someone.
I would tend to steer clear of architects, unless you want the security of them holding your hand throughout the build. Most reputable builders can
work from Local Authority building warrant type plans with ease.
If you have access to AutoCAD then have a crack yourself, try to get hold of some drawings for other work and pinch details and specifications from
them. Thats how i started, prepared my own plans then fabricated and erected my own timber frame house. Its amazing what you will learn and there is a
fair bit of satisfaction from doing your own.
Good luck.
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ChrisGamlin
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| posted on 1/5/06 at 09:31 PM |
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Cheers chaps. So whats the difference between an architect and an architectural technician or someone who can do just plans?
From the building side of things, a neighbour of ours is a builder and he's done a very nice job of his own extension, and Ive already sounded
him out as a possible to do the work, so probably my first port of call should be to speak to him and see if he can either offer advice himself or
recommend someone who can do the plans.
I have access to Autocad and did it at uni (Mech Eng degree) but that was a few years ago and Im not sure Ive got the patience/time to re-learn it
again and then produce something thats submittable. I was considering using something like this as its specifically
written for designing houses so imagine it would be much quicker than drawing everything from scratch in Autocad? The things that concern me if doing
it myself are fundamental things like roof angles, I assume if I submitted plans that say only had a 30 degree roof slope when I actually needed
something different, it would get rejected and Id have to start the process again?
Chris
[Edited on 1/5/06 by ChrisGamlin]
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Guinness
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| posted on 1/5/06 at 09:58 PM |
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Thanks for the compliment Albertz
(Two years as an architectural technician, three as an interior designer, the last 8 as a project manager, now running the regional office of a design
build company)
Chris, an architect spent 7 years at uni, so has a massive overdraft, which you are going to help repay! The architectural technician is a college
graduate who is employed by the architect to make the grand designs work / do the dirty work of actually picking up a pen / moving the mouse!
As I said everything tends to be calculation based and interlinked. The roof for example, what are you thinking of flat roof or pitched, slate or
tiled? If you go for a tile, it will have a minimum angle of installation (below which you will have problems of water going back up and into the
felt) and a weight. As long as the angle you propose is steeper than the minimum then you should be OK. The steeper the angle though the more tiles
you need to cover a given floor area. The more weight you need to be able to support. Therefore you need thicker / more roof trusses / joists. Then
you'll need walls thick enough to hold that lot up and foundations deep enough to hold the walls still!
Drainage is similar. For rainwater pipes and guttering = Roof area x rainfall x frequency. The roof area is dependant on slope, the rainfall is
calculated by region and easily found. Frequency is what you want the system to cope with, the type of event that happens every 20 / 50 or 100 years.
For foul use readily available pipe sizes for the wastes 32mm hand basin, 40mm sink, dishwasher / washing machine etc. Join them up to a soil pipe
and make sure the falls are above the minimum spec for that size of pipe / drainage run. Got to check trap sizes conform to the regs etc.
Electrics also have to conform, as does the insulation and just about everything else, sound transmission, spread of fire etc etc. It all seems a bit
daunting, but break each element down individually and it's not too bad.
The Office of the Deputy Prime Minister very kindly publish all the Building Regulations Approved Documents on the web. Here
http://www.odpm.gov.uk/index.asp?id=1130478
and for free!
Feel free to ask for help if you want.
HTH
Mike
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ChrisGamlin
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| posted on 1/5/06 at 10:15 PM |
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Thanks again Mike, we're planning on a sloped tiled roof so all that will need to be calulated in. Electrics arent an issue thankfully as my
mum's partner is a sparky and has already completely rewired the house for us.
I think first stop as you say is to speak to the neighbours and find out if they can recommend someone, have a dig through the link you gave and take
it from there.
cheers
Chris
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Guinness
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| posted on 1/5/06 at 10:23 PM |
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Chris
It's good to have a tame electrician, but it's not enough to get building regs. You'll need to have plans with positions of
light fittings / switches on them. Also you'll need an extract fan for the bog / utility room so you'll need to show them on the drawings
(ventilation) and get the sparky to put feeds and switches in for them.
Once you have building regs approval, expect a couple of visits from the inspector once you start on site. Usually when the founds go in (to check
they are deep enough), just before you cover the underground drainage (to check the falls), when the walls are half way up (to check the cavities /
insulation), and then when it's finished.
Cheers
Mike
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Aboardman
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| posted on 2/5/06 at 07:02 AM |
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for the planning dawings you will need a plan (existing & proposed), elevations (existing & proposed) to scale (1:100 is fine). on the
proposed drawings you should have dims on showing plan size and heights.
For the building regs you will need normaly a section and specification and some details about drainage, lot easier if you have manholes around the
extension.
on thing to check before starting if you house is a modern house is to check with the building inspector if you house was piled or deep strip, if it
was then you foundations could be expensive.
if i can be any help just ask
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Peteff
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| posted on 2/5/06 at 09:25 AM |
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They will most likely also want your new building to match your present building, as probably you will too, so if your roof pitch on your extension is
different to your house they will ask for it to be changed, which will mean an alteration to your plans and more expense so find out their policy. My
mate is an architect technician for a local council and does a lot of this including submitting for planning so expect to have to comply with some odd
requests like steel reinforcing in the roof depending who checks your application.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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Syd Bridge
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| posted on 2/5/06 at 09:45 AM |
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Hello Chris,
I've just gone through all of this for a new detached garage(10.5mx14m) with proper pitched roof with office upstairs, and a loft conversion for
the house for 3 more rooms for my monster sons.
Your best friend will be a builder you can trust. He'll know the building regs, and can advise on timber sizes/foundations/ technical details
needed for permissions.
I also found our local planning officers very helpful, especially after they saw the preliminary drawings I had done for them to scrawl all over.
(Also done quickly in A'cad.)
If you can do the drawings yourself, then find a good builder first, then between the two you you should be able to get the plans and permissions
without an architect or achitectural tech, and save yourself a good amount of beer money.
And as I put above, visit the Planning Office a couple of times as you do the drawings, and let the officers make their corrections on an informal
basis. This lets them think they have an active role(which they actually have) in your building. The planning officer I have dealt with told me that
'it is nice to put a face to an application, makes it less impersonal', and they also like the chance of personal involvement.
Also gives you some come-back if the inspector wants changes. Just pull out the preliminaries with the PO's corrections.
Cheers,
Syd. 
[Edited on 2/5/06 by Syd Bridge]
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ChrisGamlin
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| posted on 4/5/06 at 09:10 PM |
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Thanks for all the advice chaps, sorry I havent posted back for a couple of days
The house is a 1950's semi in a clay area so not sure what that might imply about foundations, although the neighbour builder mentioned that you
generally need to go down deeper than the existing foundations, and his were just over a metre deep.
I will have another look at the weekend and see if I can convince myself I'll be able to rattle something passable up
cheers
Chris
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Aboardman
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| posted on 4/5/06 at 09:42 PM |
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if you are stuck let me know i will be able to get you a specification for the building regs side of it, and check over your drawings if you wish.
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ChrisGamlin
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| posted on 5/5/06 at 05:49 PM |
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Many thanks, much appreciated. I'll maybe give it a go over the weekend and then see what you think if you really dont mind having a look over
the plans
Chris
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ChrisGamlin
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| posted on 23/5/06 at 08:35 PM |
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Hi chaps
Im now drawing my plans by hand (dug out my old A2 drawing board I used at school!) as the CAD type packages are either too simple and don't
produce the desired result, or need about 4 years training in them!
A couple of quick questions to the architect types among you....
On the planning application form it says that all trees to be removed or left have to be included in the drawings. What do they class as a tree
though, Ive got one single Conifer thats about 3m tall that will be chopped down, plus a half dead lilac "tree" thats also no more than
about 8ft high. Do I need to include them in the elevation drawings?
Also, do I include things like fences etc in the elevation drawings? I will mark them on the plan drawings to show the boundaries but wasnt sure if
they needed to be included in the elevations too.
To give you an idea of where the fences are, its the one joining up to the house in the 3D drawing below, which I did using the app I linked to above,
a pretty nifty app for the 3D stuff but doesnt produce very good plans / elevations unfortunately, and doesnt allow you to print out to scale so would
need trial and error to get them the right size on paper to be submittable
 
House 3D
cheers
Chris
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Aboardman
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| posted on 23/5/06 at 09:46 PM |
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no need to show fence or trees on elevation drawings, but would note them on the plans.
a good tip would be to go to you local council web site and to the planning department section most council have the plans available online and you
can download them in pdf format it will show the typical amount of information that is required on the drawings.
here is a typical application and it is not one of mine,
http://www.blackburn.gov.uk/upload/pdf/10_06_0169.pdf
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JoelP
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| posted on 23/5/06 at 09:59 PM |
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my approach would be to simplify the forms by chopping the trees down in advance!
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jollygreengiant
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| posted on 24/5/06 at 02:23 AM |
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One bit of advice, on the plans make sure that you make the foundations of the extension deep enough so that in the future it could be possible to
extend upwards over the top of the existing single storey extension. If you don't do it yourself then should you come to sell, then it could be
useful to prospective buyers.
Oh I used an architect and found an excelent rcomended builder from start of planing to finish of build (single storey of top of exisiting garage)
approx 10 months, had to wait for builder but was worth it (until mother-in-law moved in).
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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ChrisGamlin
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| posted on 24/5/06 at 06:32 AM |
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Cheers chaps, I have found my local planning office website which does have all the submitted plans scanned in, and having seen a couple of them
such as these, I think
I could produce better drawings even with my eyes closed!
I was told that for the planning phase for an extension my size, the drawings don't need to show the foundations as such, certainly havent seen
anything on the plans Ive seen on the local authority website? Also I think all foundations now have to (?) be the same depth regardless of whether
its a single storey or not don't they?
cheers
Chris
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ChrisGamlin
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| posted on 15/6/06 at 09:42 PM |
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Hi chaps, just resurrecting this old thread to ask a question to the architect / builder types among you.
On a pitched roof, what is the minimum / maximum angle of slope you can have? If it makes any difference, looking at the above 3D image, the extension
will be on the side of the house with a single plane pitched roof leaning up against the existing side wall of the house (perpendicular to the slope
of the main roof), and will span approximately 3.8m
cheers
Chris
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Peteff
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| posted on 15/6/06 at 11:17 PM |
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I'm not an architect.
but a builder would go for the least pitch to save on materials and the roofing material would be the deciding factor, around 30* is common though.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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Aboardman
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| posted on 15/6/06 at 11:20 PM |
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the min roof pitch will depend on your roof covering,
concrete tiles can go down to 15 deg but very limited choice on tiles and to be honest does not look very good, slates need to be laid ideally at 30
deg but you can come down to 25 if you increase the lap.
i would say a roof pitch of 20 - 25 would be about right.
you may wish to check out the tile company for techincal and design data.
http://www.marleyeternit.co.uk/
www.lafarge-roofing.co.uk
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ChrisGamlin
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| posted on 16/6/06 at 04:47 PM |
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Cheers, so its totally dependent on tile used rather than any blanket minimum?
The reason I ask is because with a 25 degree slope, the roof would meet the house wall just above the window sill of the upper side window which
obviously isnt desirable and would add complication insetting the window into the roofline partually. I'll do some tile research then!
cheers
Chris
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Aboardman
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| posted on 16/6/06 at 05:12 PM |
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20 or 22.5 deg are ok to use with a marley modern tile.
you should allow 2100 to underside of fascia board and a 150mm fascia board, if you are coming under a window allow 150mm below window to allow for a
flashing.
you could alway pitch it on 3 sides, instead of gables on either end.
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ChrisGamlin
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| posted on 16/6/06 at 05:56 PM |
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Yep the plan was to pitch it at least on 2 sides (across the front too) so it linked into the front of the house. The front of the extension (a
garage) will extend about a metre further out from the front of the house, so the pitch roof would continue across and create a porch type overhang
over the front door. Actually the extension wont extend right back to the rear of the house, so pitching it there as well might mean it cleared the
top window completely.
Thanks
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ChrisGamlin
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| posted on 16/6/06 at 07:08 PM |
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Something like this
 
Extension
Thats about 20 degree slope on all three pitches, but could go up a bit higher if needbe, but Im not sure if 3 equal slopes like that is the
"done" thing, any reason why not?
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