Costs and budgets – how to plan, predict and understand your self-build costs.
Typically construction costs are approx. £1400-£1700 per sq m
Therefore best case scenario you could build a 71 sq m house (£100k ÷ £1400 = 71 sq m). Technical housing standards – nationally described space standard would say 71 sq m this is roughly a 3 Bed house.
Phase 1 – the budget
Across the U.K. 80% of builds are either on or under budget, the remaining 20% that are over budget are usually self-build home owners.
Factors influencing the budget level
- Borrowing ability
- Must haves/nice to haves
- Level of hands on contributions. Don’t give up your £400 a day job to be a £70 a day labourer, that isn’t smart math.
- Wider economy factors. Building materials are going up so make sure you negotiate a good deal.
- Research and market knowledge.
- Who you know, is it a benefit or a hindrance? Always plan for a commercial cost (worst case scenario).
- Design ‘freeze’ can it even be possible? On site changes are usually costly.
Preparation, preparation, preparation.
It is key.
The budget can be established at a high level by several means.
- Cost per sq m Construction cost calculator
- Subcontractors will price the scheme from outline drawings to give you a guide price.
Reduce your uncertainty by stress testing your design options before planning.
Phase 2 – the cost plan
A measured and considered means of developing the the budget into a plan which is more robust for procurement/control.
Use the drawings to give you a breakdown of labour and materials to give you quantities.
How do we figure out the inputs needed? Information is available from various sources.
- There are published price guides such as spons, laxtons or similar.
- Talking to people who have done it before, materials are easy to source but labour is harder to shop around for.
Don’t forget prelims, pay to make sure the site can operate and be safe
A 10% contingency should always be factored in for the unknowns, what have you forgotten about.
Who should do it?
Then of course there is always project managing individual trades people and DIY
Look at the risks associated with the project and pass it to someone who can handle it. If you can’t manage the risks then give them to a professional that can.
By knowing in advance the nature of the scope of works you have the ability to juggle the cost plan to suit your procurement performance.
You now have a plan, stick to it.
- Be present at valuation stages
- Be diligent for front loading
- Be prepared for up front requirements from suppliers
- Try to avoid advanced payments
- Revisit your cost plan every time you want to buy
And remember variations means cost changes!
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