Does anybody know where I could possible get hold of cavity wall specs ? basically I'm looking at managing a extension project myself but I want to be sure that everything is done right and according to BC. Some of the builders I have had in for a quote tell me that for the floor be it solid or wooden, they have to dig about 8" down and then build it up with a mixture of hardcore, insulation and DPM, is this correct ?
Any advice/help will be greatly appericated.
This should be specified by your archtect. 8" sounds about right. It will certainly be checked by building control during the construction.
John
The first step is to commission an architect to draw up the plans. (They do not have to be done by an architect but need to contain a full construction specification so it is often an architect who does them)
He will visit the site to measure up and discuss with you what you want
The plans will contain all information regarding footings construction materials insulation roof structure etc. He would also commission a structural engineer should one be needed
These plans are then submitted to the local council building department for approval.
The architect will normally know if the plans will also require planning permission
Once the plans have been passed you would then use them to get quotes from builders based on those plans or from individual tradesman for each aspect of the work
When I last did this I also ordered all materials and contracted in such labour as I needed so essentially I acted as the builder would have done
As project manager you will then supervise the builder/tradesmen to see that they follow the plans and do the work to the standard you require you would notify the building control dept as required to inspect each stage
I know other people who have started the process by asking a builder for a price based on talking with them and then the builder arranged for the plans to be drawn and submitted and then carried out the work
Tony
Out of interest, how much did the architect charge? I've been quoted 10% of the project cost by a RIBA architect - but it's a bit chicken/egg - I need the plans to cost the project.
Thanks, Rob
Hi rob
Was a few years ago & I can't remember the fee
Unfortunately he died suddenly (in his 40's) a couple of years after otherwise I would have asked him for you
Tony
How are you going about getting Building Regs approval for your extension? Assuming you're in England or Wales (Scotland may be different) there are two different approaches which you can adopt. The more usual one is to draw up (or pay someone else to draw up) detailed plans which contain the full technical details of how the building will be constructed - and get them approved *before* getting quotes from tradesmen for the actual work. These will contain details of the cavity wall construction, floor construction and insulation, roof construcion, door and window specs, etc. - and leave little room for argument.
The alternative approach is to do it on a Building Notice - where you submit much less detailed plans and then negotiate each detail with the Building Inspector as the work progresses. This gives you more flexibility to 'refine' the design but also makes it much harder to get fixed price quotes from tradesmen because the BCO might insist that they do something they weren't expecting, thus adding to the cost.
It's a good idea - especially if you're doing your own plans - to go to have a chat with a BCO at your local council and find out exactly what they'll be looking for before you start. If it's obvious from your approach that you want to do it right, but are not quite sure what to do, I have always found them to be very helpful and supportive. They'd rather help you get it right first time than get into a dispute when they come to inspect something which
*hasn't* been done right.If you're doing your own project management, this book
Yes it is worth speaking with BCO and if others nearby have had extensions built recently you may be able to get some good info about the nature of the ground and likely footing depth issues, routes for foul water and storm drainage pipes that may affect the groundworks as many people have had unforeseen expenses once the digging started. However if your architect is local he may have good knowledge anyway
There are lots of cautionary tales to be told about building work e.g.
My next door neighbour has last month applied for a single storey garage/store attached to the side of his house as has been told by BCO (not Planning) that he cannot simply put in a concrete raft for this but must put in proper footings in case in the future there is an application to add an upper floor (the difference in cost is 4 extra skips for the waste say £600 and £1200 extra for the concrete and then the extra time and labour which has doubled the cost of the project)
Tony
I was thinking about going the lawful development route and I have been speaking to the planning dept about this. I live in London in the borough of Barnet. My Ext is going to be around 18m2 (6x3) with a flat roof at the back of my house, my neighbours has the same ext already. Currently the space is occupied by a conservatory which will get removed.
Only eight inches?.. mine was dug down by about 6 feet and a concrete raft laid with more steel in it than a motorway bridge.. then the floor was laid about 2-3 feet thick with more steel in it. If it ever sinks I should be able to put a cable under each corner and lift the damn thing if I can hire a big crane.
Totally ott as the house next door has 3 foot deep strip foundations and there aren't any mines or anything like that here.
On Fri, 22 Jun 2007 13:56:34 +0100, a particular chimpanzee, "Roger Mills" randomly hit the keyboard and produced:
With the caveat that the BCO won't design it for you, and will get very pissed off very quickly if you start asking him to.
Not if it's in his area, there seems to be a number that will moonlight out of area.
AJH
I didn't suggest that he would. But hopefully he will tell you what U value you need to achieve, and where to find tables of material properties that you will need when working out how to achieve it, and things like that. When I did my extension on a Building Notice, I bounced my plans informally off a BCO and got some very useful pointers on bits which I needed to modify. I don't know whether all councils are the same, but my council always has one 'duty' BCO in the office whom you can drop in and see if you need advice.
On Sat, 23 Jun 2007 15:55:37 +0100, a particular chimpanzee, "Roger Mills" randomly hit the keyboard and produced:
No problem with that, but it's the owners who ask, "what size rafters do I need?", "how much insulation do I need in the walls, roof and floor?", "what's a damp-proof membrane?". I've some single storey extensions in progress that I've spent more hours on than I have on whole housing estates or multi-storey office blocks. The owner saves £500 on a set of plans, everyone else who puts plans in has to cover the £500 of extra work it takes to sort out their mess.
We were thinking about having a conservatory built, and since we've had "seasonal movement" in the past, I asked our tame structural engineer about the foundations for the conservatory - he was talking about
2m foundation, or micropiling. The foundations of the house date from the 1890s and I doubt if they're 18" deep ...We didn't bother. I built a deck instead.
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