How to decide how big to build?

[Ed_]

HI all,

at the design stage and feeling a little unsure how much we can afford to build.

Rules of thumb vary say £1500 to £3000+, so thats half the size...

It's hard to get proper costs without a proper design, but we don't want to create a proper design without some feedback on the costs first! Especially when planning permission timescales are accounted for, so how do you all do it?

 

Related question - lets say we are slightly ambitious in size and it ends up costing too much, what potential is there to economise later? Everything needs to be finished to get a proper mortgage so is it feasible to leave half the house as a shell for example?

 

Thanks,

Ed

[ToughButterCup]

21 minutes ago, Ed_ said:

..., so how do you all do it? ...

 

Iterate.

Start somewhere - anywhere in the cycle.

• Ooops too expensive. 
• Replan
• But that means we can't [...]
• Replan
• Oh look, I found a really much cheaper way of [...]
• Replan
• @Onoff does one of his brilliant posts and that makes you
• Replan
• @SteamyTea 's latest screed of numbers and thoughts  makes you realise you haven't thought about [...]
• Shit ! Too late, con't replan
• But with a bit of a compromise (replan ) we could [...]
• @nod posts his latest build numbers and you get depressed because he's a Whirling Dervish and you aren't ( me neither )
• Argggghhh, runin' low on money ...
• Replan
• And then you get to DIY MAX. Welcome to the club baby!

Eight years in to our build and the iterative cycle is much smaller, and less consequential now than it ever was. But it still happens every day. 

 

Start anywhere at all. Just start.

[Dunc]

I haven't got a spade in the ground yet so not best placed to advise on future economies. But I have been through the "what can we afford" question very recently.

What do you want to achieve in three key areas:

Style: Architecturally interesting or simply functional?

Performance: a bog standard building regs house? A passive house?

Build: will you do any practical or management work, or do you want a project manager or main contractor to do it all?

 

Talk to architects/designers. Some we spoke with gave us expected costings in the £3000-£4000/sqm. These were architects whos portfolios clearly show "flair" (balconies, ovehangs, fully glazed walls...i.e. expensive things to engineer) and/or who work most often to passive standards. Others suggested lower costs per square meter and clearly work more with self builders who have a tighter budget and want a nice, but fairly simple house. Even these latter types started at >£2000/sqm. I think unless you're very hands-on, the lower end of the range is not going to be achievable. YMMV.

 

Cost per area doesn't usually include the plot itself. Or the professional fees associated with that...I'm rapidly finding that I didn't budget for all sorts of things that do add up. £180 just to register the address, for example. Fees for servitude to get services to site. Site surveys of various sorts. Insurances...

 

I think self build is a bit like the stock market; it's an investment that contains an element of risk.

[ProDave]

We built the size of house we wanted.  Previous house was 5 bedrooms that we ran as a B&B and we wanted to exit that business and have a normal 3 bedroom house.  But we wanted ample sized rooms and we knew what rooms we wanted.  Even so our 150 square metre "ordinary" house was not in the end very much smaller than the previous 5 bedroom house.

 

Our key requirements were accommodation to suit our needs, and to be flexible, lower council tax, and lower heating costs than the old house.

 

The site and available space on it led the basic shape and orientation of the house and which way was south and which way had the views (not the same) dictated a lot about the layout.

 

Don't fall into the trap of building a massive house because you can.  I wired a new build like that and when I went back some time later to do the garage, after the first winter, he was bitterly regretting building such a big house that he struggled to keep warm and cost a fortune in heating bills.

 

Cost per square metre can be hugely influenced by careful purchasing and doing a lot yourself.  e.g. a Howdens kitchen with a good worktop can be every bit as good as some posh German or Italian bespoke kitchen.  But that leads into you can only ever have any 2 of the following  :  Good, Cheap, Quick.

 

If you think you are going to be short on cash and might want to pause the build part way, one option our neighbour did was build a dormer bungalow but did not do the upstairs straight away.  It was built with attic trusses so the basic structure was there from the start, but it was initially completed, signed off and occupied as a simple bungalow.  It was some years later he then finished the upstairs and added the extra rooms.

[Ed_]

One of the things i'm thinking about is the basement.

Its a walk-in basement because the site is sloping and for a number of reasons it just makes sense to do it, and obviously it cant be done later. But is it possible to erect the basement structure, not even insulate it, just block it off and for that to be signed off?

Because if so that gives me a £50-100k buffer in the worst case scenario.

[ProDave]

The basement will certainly have to be structurally formed as a basement and waterproofed.  Others who have done a basement will have to comment if the insulation can be left until later.  I see no reason it cannot be left as an empty basement with no details finished initially.

 

Other money saving tips might be dirt cheap kitchen and rip it out and fit what you really want later.  Outbuildings like garages and sheds can wait until later as can a lot of the landscaping.

[saveasteading]

20 minutes ago, ProDave said:

you can only ever have any 2 of the following  :  Good, Cheap, Quick.

...say suppliers who are expensive or slow.

 

Many of my projects as a design and build contractor were negotiated when the client realised their best quote was still way over budget. "Somone says to speak to you".

Response:

Of course it will be good. It will also be as quick, probably quicker, and much cheaper than those people.

Of course huge acceleration can increase cost. The client can decide.

It is all relative.

 

[saveasteading]

13 minutes ago, Ed_ said:

But is it possible to erect the basement structure, not even insulate it, just block it off and for that to be signed off?

Yes. Don't call it a basement but an "undercroft". This is a perfectly normal thing to do on a hillside. Some become basements, some are storage accessed from outside, and others remain as voids.

You will have to debate insulation, or lack of it, with the bco.

[Ed_]

6 minutes ago, saveasteading said:

Yes. Don't call it a basement but an "undercroft".

Excellent idea!

[saveasteading]

22 minutes ago, saveasteading said:

insulation, or lack of it,

Once you have a structural principle you can plan this. If it remains an  unheated space then you need to insulate the suspended floor. 

 

My go-to for such a site is sleeper walls at about 4.5m centres, with beam and block over the whole floor.

Advantages, other than cost, are that it is semi-skilled and man-handleable whatever the weather and access constraints.

[Alan Ambrose]

>>> the insulation can be left until later

 

Suggest not - you need a waterproof, insulated concrete box. You don't have to fit it out, but you may want to put a plant room, utility, storage etc in there which will mean some minimal fitting out e.g. electricity, light etc.

 

Basements are usually expensive, but if your ground demands deep foundations or is very sloping it may not be a lot more expensive than not having one.

[saveasteading]

43 minutes ago, Alan Ambrose said:

Basements are usually expensive

Very. Basements are fighting against water ingress and ground stresses,  and  they need excavation and support.

Undercrofts on a slope don't, but they are a fair bit dearer than building on the ground ( except  those thick slabs with 4 layers of reinforcement we see sometimes).

 

I did a sports hall on a steep slope once. Our method was as above, as compared to the clients 'suggestion' from a respected SE. Saved £50k, maybe much more, plus it was buildable despite mud everywhere.

And the same another couple of times when it was my design from the outset. What you have to live with though is sturdy cross walls supporting the beams.

You can use concrete planks instead but it isn't necessary for light loads.

 

Insulation can go on top of the structural floor, then screed on that.

[twice round the block]

3 hours ago, Ed_ said:

HI all,

at the design stage and feeling a little unsure how much we can afford to build.

Rules of thumb vary say £1500 to £3000+, so thats half the size...

Go for £3000, then hopefully you won't have a nasty surprise. 

3 hours ago, Ed_ said:

It's hard to get proper costs without a proper design, but we don't want to create a proper design without some feedback on the costs first!

Have you purchased the plot yet ?

3 hours ago, Ed_ said:

Especially when planning permission timescales are accounted for, so how do you all do it?

If you've purchased a plot, what build construction do you want, style of building, number of bedrooms  

3 hours ago, Ed_ said:

Related question - lets say we are slightly ambitious in size and it ends up costing too much,

That's where part of your 100k contingency fund comes in.

3 hours ago, Ed_ said:

what potential is there to economise later?

Stay in your static caravan for another year while you work that one out.🤣🤔

3 hours ago, Ed_ said:

Everything needs to be finished to get a proper mortgage so is it feasible to leave half the house as a shell for example?

Depends on your mortgage terms and conditions.

Also depends on how much money you are borrowing, and if a lender could recover ALL THEIR MONEY if the unit is auctioned off.

3 hours ago, Ed_ said:

 

Lot's of self builders, build vast houses if they've got a plot big enough to take it. ( I'm guilty)

Rattling around in a big shell is not very pleasant. Then you need large item's of furniture to fill the room's.

 

The average mass build 4 bed estate detached house has a foot print of 10m x 12m, go round some show homes and see how much space you really need.

 

The whole self build game comes down to money.

How much capital and assets you have, and how much you would comfortable with  borrowing on a mortgage if you had too, with out bankrupting yourself and family.

 

First job is to get rid of the rose tinted glasses and do a reality check, as this journey WILL be stressful.

[DevilDamo]

Engage an Architectural Designer to produce the proposed drawings along with a basic (for now) specification and the have it costed by a QS.

[saveasteading]

16 minutes ago, twice round the block said:

to get a proper mortgage so is it feasible to leave half the house as a shell

feasible but most don't like it. Most lenders are completely unimaginative and want a building to be finished.

the same applies to insurers...I'm sure we are paying on the finished value, not the interim.

[Kelvin]

Like @ProDave we built to the size we would use with reasonably generous room sizes. Our goal is to use every sqm of the house we built. Our previous house was  more than twice as big as this and we used half of it 90% of the time. This house feels much bigger than it is (210m²) because the main room is open plan and clear sightlines to the other rooms. Our previous house had an enormous  6m x 4m vaulted hallway and balconied/bridged staircase. It was a nice wow feature to walk into but it was just a hallway/staircase. 

[JohnMo]

5 hours ago, Ed_ said:

at the design stage and feeling a little unsure how much we can afford to build.

No point starting the journey if you want a house, but can only afford to build a shed.

 

You must have an idea of what you need at the end of the journey? Otherwise you wouldn't even be looking to go this direction.

 

Going underground, even on slope can become a money pit quite quickly - limited funds you need to reduce risk, not increase it. We are a hill and spent £50k before we got out the ground, that is cheap. We spent another £70k landscaping and retaining slope. That's all before we started building.

 

If you think you need 250m², you in reality possible only need 200m² or less. 200m² is big roomy house, 3 double bedrooms with ensuite s, big lounge and kitchen. As mentioned big rooms are difficult and if done poorly look rubbish.

 

Use where you live now, as a yard stick. Are the rooms sized well, need a bit bigger, bit smaller, need twice as big start questioning yourself.as you need a reality check.

 

 

Edited August 13 by JohnMo

[garrymartin]

4 hours ago, ProDave said:

Outbuildings like garages and sheds can wait until later as can a lot of the landscaping.

Unless you want to take advantage of any VAT savings on the garage and on the landscaping (assuming you submitted a landscape plan with your application)...

[JohnMo]

26 minutes ago, garrymartin said:

(assuming you submitted a landscape plan with your application)...

And have a garage on your plan, otherwise you can't get it VAT free.

[Kelvin]

We built the garage first. It gave us a large secure storage space to stage materials and a workshop to work in when the weather was crap. 

[Pendicle]

I’m still at demolition stage but regards price, it all depends what kind of self build you’re doing DIY, builder provide super structure you then take over and possibly project manage with contractors or turn key where a builder does everything. There are a number of variables in between but the costs are subject to how you intend to self building, turn key being the highest. Don’t underestimate the surveys costs they add up and keep a healthy contingency. We are building the same size and footprint of original house, as that works for our plot, if I was building on a different plot I would know doubt build a different layout but think the footprint would be the same as it has everything we need and gives us some flexibility. Every plot is different and that may also determine price from foundation design to access of utilities. Maybe give us a bit more information. 

[Bozza]

Lots of good advice so far @Ed_.

 

Most self builders have a finite budget and have to build to it.  It’s easy to get carried away (per many episodes of Grand Designs) then face genuine financial hardshape or even bankruptcy, or an unfinished house. Don’t be that guy.    No house is worth that.

Better to build smaller with good design, and good quality.

 

We were tempted to build bigger than we did (214 sqm) as at the time each extra 1sqm was going to cost us an extra £1k, due to economies of scale.  It took real self discipline to say no and stick to budget/size.  The day before we moved in, my wife was made redundant.    We coped financially because to self build was a heart decision, but the choices we made were head decisions.
 

As it turns out we could have had a great house for maybes 180sqm so could have gone smaller.

 

Even turn key as we were there’s lots of ways to save money.  Make good choices.

 

what size house do you wish to build?  And for how many people?  And what’s your budget?
 

 

 

 

 

 

[Kelvin]

We also built it for us, not the next owners. While technically it’s 4 bedrooms we configured it for two. The other two bedrooms are a study (downstairs) and an open plan sitting room upstairs. To convert that back into a bedroom will require adding in a wall and a doorway so easily doable. But it currently gives us the whole of the top floor as a bedroom suite. I wasn’t sure how well we’d use the upstairs sitting room but it’s used a lot more than we thought. 

[Dave Jones]

On 13/08/2024 at 13:45, Ed_ said:

HI all,

at the design stage and feeling a little unsure how much we can afford to build.

Rules of thumb vary say £1500 to £3000+, so thats half the size...

It's hard to get proper costs without a proper design, but we don't want to create a proper design without some feedback on the costs first! Especially when planning permission timescales are accounted for, so how do you all do it?

 

Related question - lets say we are slightly ambitious in size and it ends up costing too much, what potential is there to economise later? Everything needs to be finished to get a proper mortgage so is it feasible to leave half the house as a shell for example?

 

Thanks,

Ed

 

work backwards from the m2 sale price for your location. 

 

You dont want to spend 500k when it sells for 250k

[Mike]

1 hour ago, Dave Jones said:

work backwards from the m2 sale price for your location. 

 

You dont want to spend 500k when it sells for 250k

Yes, that that's a key consideration. Build to suit the neighbourhood and don't over-develop / under-develop the site - or if you do, be aware that that's what you're doing and what the consequences may be.

 

On 13/08/2024 at 16:28, Ed_ said:

But is it possible to erect the basement structure, not even insulate it, just block it off and for that to be signed off?

In principle, but the floor between it and the rest of the house above will need to be thermally insulated to Building Regs standards as it it were to permanently stay that way, without heating, with ventilation, the same as any other unheated under-floor void. Though you could still insulate it, read for future conversion.

 

Since it would have been signed off that way, you'd need a new Building Regs application to incorporate it into the house at a later date.

 

Or you could go half way - build as part of the house, but not divide it up into rooms and install the minimum of services, so it can be used as a games room / gym.