Another extension question

Beenie

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timpal

I don't think you're going about it the wrong way at all. Theres a lot of negativity here.
There isn't such a thing as a right way.
Each project evolves in its own way.
If you want to tinker about and find out what approximate costs for each bit might be, fine.
You're probably not spending any money doing so. And as long as you take them with a pinch of salt, fine.
There are some many variants in how things can be designed, doing some research before you employ the professionals is fine. We do appreciate people who invest a little time in understanding how things are built.

So long as you have it fully designed, before you go to tender/ start, that's the important thing.

As to piling costs.
It will vary. A lot. Find a local piling company email your planning drawings and they'll usually give you a quote. They quite often have in house engineers so will be fairly well informed. In fact your project engineer will not usually design piling, just say what load will go onto the piles.
Being 30m2 possibly not worth bothering with ground beams, maybe just a nice thick RC raft slab. Then you can pretty much put loads wherever you like.

Recent piling quote in Surrey for about 30m2 extension. £5,500 for 14no. CFA (bored rather than driven) 200mm dia piles to 8m. Just for piles.

Another one on south coast. 100m2 extension. 28no. 220mm piles to 6m. £11k. Had another quote for 15k.

All of that would be + slab and/or ground beams.

Or if you're handy with a spade/ digger. Dig a hole yourself and find out if you can get down to something decent (soil wise). If you're local authority has a good building control department, they may come out and have a look on site and say if you can use trad footings. (just be safe with shoring up any excavations).

And I would say its edging up to £2-2,500/m2 + specialist items (kitchen, special ground works etc).

Good luck.

timpal

I don't think you're going about it the wrong way at all. Theres a lot of negativity here.
There isn't such a thing as a right way.
Each project evolves in its own way.
If you want to tinker about and find out what approximate costs for each bit might be, fine.
You're probably not spending any money doing so. And as long as you take them with a pinch of salt, fine.
There are some many variants in how things can be designed, doing some research before you employ the professionals is fine. We do appreciate people who invest a little time in understanding how things are built.

So long as you have it fully designed, before you go to tender/ start, that's the important thing.

As to piling costs.
It will vary. A lot. Find a local piling company email your planning drawings and they'll usually give you a quote. They quite often have in house engineers so will be fairly well informed. In fact your project engineer will not usually design piling, just say what load will go onto the piles.
Being 30m2 possibly not worth bothering with ground beams, maybe just a nice thick RC raft slab. Then you can pretty much put loads wherever you like.

Recent piling quote in Surrey for about 30m2 extension. £5,500 for 14no. CFA (bored rather than driven) 200mm dia piles to 8m. Just for piles.

Another one on south coast. 100m2 extension. 28no. 220mm piles to 6m. £11k. Had another quote for 15k.

All of that would be + slab and/or ground beams.

Or if you're handy with a spade/ digger. Dig a hole yourself and find out if you can get down to something decent (soil wise). If you're local authority has a good building control department, they may come out and have a look on site and say if you can use trad footings. (just be safe with shoring up any excavations).

And I would say its edging up to £2-2,500/m2 + specialist items (kitchen, special ground works etc).

Good luck.

brigittejohn

I agree with the initial post that one needs to get a very rough idea of costs sometimes, long BEFORE hiring professionals like structural engineers and architects.
So far I already spent more than £2,000 on this and I really would have liked to know that the project would cost about £70,000 before! then I would not have asked for the plans at all, as this is way over what I am prepared to spend.
Now I have to ask for new simpler plans and pay again.

I really don't understand how people keep to a budget when doing such works, as everything seems to be rough estimates and percentages, which I hate. Very very nervous about doing any work at all now.
This is not even talking about the ridiculous party wall rules which are money making machines for surveyors.

System

brigittejohn wrote: »

I agree with the initial post that one needs to get a very rough idea of costs sometimes, long BEFORE hiring professionals like structural engineers and architects.
So far I already spent more than £2,000 on this and I really would have liked to know that the project would cost about £70,000 before! then I would not have asked for the plans at all, as this is way over what I am prepared to spend.
Now I have to ask for new simpler plans and pay again.

I really don't understand how people keep to a budget when doing such works, as everything seems to be rough estimates and percentages, which I hate. Very very nervous about doing any work at all now.
This is not even talking about the ridiculous party wall rules which are money making machines for surveyors.

It is literally impossible to give a precise costing for something that isn't designed or specified! If you want cost certainty you have to pay for professional services and a proper design team from the outset (so architect, engineer, quantity surveyor min) unfortunately, none of them are interested in working for free until you decide if something is too expensive or not. The cost of materials varies day to day and brexit is having a huge impact on these at the moment.
The problem is people tend to be overly optimistic when imagining the true costs of construction projects, no one factors in professional fees or VAT into costs and people still band about the impossible £1k per m2 all over the internet. At the moment when I'm designing, I'm looking at 3k per m2 to try and get things in to a clients budget but it inevitably means that you have to tell people they can't get what they want

teneighty

the_r_sole wrote: »

It is literally impossible to give a precise costing for something that isn't designed or specified!

They aren't asking for a "precise" figure, they just want an approximate budget estimate to see if their ideas are likely to be within their projected budget.

I am more than happy to give my clients some approximate figures, even approximate piling costs if appropriate, otherwise I could be designing something that far exceeds their budget. A point illustrated nicely by Brigittejohn where design fees were wasted because the "architect" didn't bother to check. It would be nice if all clients had limitless funds but in reality we all have to work within cost constraints.

At a very early stage it should be possible to prepare an approximate budget estimate based on a simple square metre rate depending on the nature of the project with some contingencies thrown in as necessary to cover special items.

Good post by timpal which shows any good designer/builder should have lots of experience of their local conditions and build costs so should be able to put together some rough figures fairly easily. I was rather baffled why the OP thought that just because they are on clay they need piled foundations, there must be something more here we are not being told.

System

teneighty wrote: »

They aren't asking for a "precise" figure, they just want an approximate budget estimate to see if their ideas are likely to be within their projected budget.

I am more than happy to give my clients some approximate figures, even approximate piling costs if appropriate, otherwise I could be designing something that far exceeds their budget. A point illustrated nicely by Brigittejohn where design fees were wasted because the "architect" didn't bother to check. It would be nice if all clients had limitless funds but in reality we all have to work within cost constraints.

At a very early stage it should be possible to prepare an approximate budget estimate based on a simple square metre rate depending on the nature of the project with some contingencies thrown in as necessary to cover special items.

Good post by timpal which shows any good designer/builder should have lots of experience of their local conditions and build costs so should be able to put together some rough figures fairly easily. I was rather baffled why the OP thought that just because they are on clay they need piled foundations, there must be something more here we are not being told.

The post I quoted was someone saying they wanted cost ideas before starting, that they don't understand how rough estimates and ball park figures are useful in keeping on budget.
With no design and no professional input theres nothing to cost. I'm sure you charge for your time...
Square meter rates are a poor way of estimating costs for domestic alterations and extensions in my opinion, that's why we always err on the side of caution when advising clients, however 90% of clients ask us to include things that they want in the tender package to see if they can afford it in the current market then wonder why their project is above their budget.
Either they need professional advice and take on board what they are being told in terms of costs in the local market then design accordingly or design what they want and see how much they have to cut to get on budget - it's amazing how many come in quoting figures from the internet which are measurably far away from real world costs of using a main contractor to carry out works, and then dont believe the advice you are giving.

Furts

brigittejohn wrote: »

I agree with the initial post that one needs to get a very rough idea of costs sometimes, long BEFORE hiring professionals like structural engineers and architects.

For everyday extensions and conventional building countless consumers could do their own budget figures. It is simply a matter of sketching out what they require, converting this to floor area and then slotting it into the tables in the likes of Homebuilding and Renovating Magazine.

I am all for professional help to guide consumers and I also maintain it is a little like chicken and egg. There is no way budget figures can be produced without first having a concept drawn out. Hence this means having the assistance of a professional. One could then argue that if brigittejohn is unhappy at paying professional fees then a DIY approach could have been undertaken. This is why the tables exist, that is why the magazines exist.