Manage your self-build or hire a main contractor?

Hire a main contractor if you want one builder to coordinate the agreed work. If you hire trades directly, you take on the scheduling, purchases and payment gaps yourself, so compare both routes after allowing for your time, delays and mistakes.

What each route involves

A main contractor agrees to deliver the house, or an agreed stage, under the contract’s pricing terms. They hire and manage subcontractors, order materials and sequence the work. You deal with one party. Even on a fixed-price offer, check exclusions, provisional sums and price-adjustment clauses: the contract decides which risks the builder carries.

Managing the build yourself means hiring the groundworker, framer, roofer, electrician, plumber, plasterer and other trades directly. You decide what happens next, order or approve materials, pay each trade and keep the schedule moving. Each trade answers to you, so you must document and pursue problems separately.

Project managing can cost less because you avoid the contractor’s coordination and risk margin. Delays, missed trades and rework can absorb that saving. Price both options on the same drawings and specification before choosing.

Can you give the build enough time?

Expect daily decisions and site visits throughout construction. If you have a full-time job, decide how you will handle daytime calls, deliveries and urgent questions. Include any leave or reduced working hours in the cost comparison.

You need to understand the order of trades, when inspections happen and how to recognise work that is below standard. An architect or engineer can help, but their time must be included in the appointment and fee. Ask a quantity surveyor or experienced builder to review your trade list and programme before committing.

For each trade, collect insurance certificates and agree the scope, price and payment stages in writing. See insurance when you project manage. Keep a cushion for mistakes and delays in your contingency, and reconcile individual invoices with your lender’s stage payments.

What you still do with a main contractor

You pay the contractor’s margin for coordination and the risks allocated to them. Choose carefully: check references, inspect finished houses and confirm insurance. A cheap quote with important omissions will not stay cheap.

Agree a written contract covering scope, price, programme, payment stages, delays and variations. Settle the design and specification before work starts where possible; later changes can add cost. The contractor is answerable under the contract for their subcontractors’ work, but the scope and remedies still need to be clear.

Compare the responsibilities

Task	Who handles it?
Hiring and pricing trades	You on a direct-trades build; the contractor under a main contract.
Sequencing work and ordering materials	You on a direct-trades build; the contractor under a main contract.
Paying trades	You pay each invoice directly, or pay the main contractor in stages and they pay subcontractors.
Fixing defects	You pursue each trade directly, or pursue the main contractor under the contract.
Design, planning and certification	You and your professionals on either route, usually separately from the contractor.
Price risk	You coordinate separate prices and gaps with direct trades. A main contract allocates risk through its terms, exclusions and variations.
Construction safety coordination	You must appoint a competent project supervisor for the construction stage where required. A main contractor can accept the role if competent.

On either route, obtain planning permission before starting; see planning for a one-off house. Building Regulations apply and you must name the builder in the commencement documents. The normal statutory certification route also requires an assigned certifier, a registered professional (often your architect or engineer) who inspects the build and certifies it meets the Building Regulations; the opt-out is explained under the certification heading below.

Agree who arranges works and liability cover and check the lender’s conditions. Your lender will want to know who is building before approving drawdown. Discuss the route early, including any fixed-price-contract or experience requirements; see lender insurance requirements.

You remain the client for safety duties

Use competent designers and contractors. Appoint a project supervisor for the design process (PSDP) and a project supervisor for the construction stage (PSCS) where more than one contractor is involved, there is a particular risk, or work exceeds 30 days or 500 person-days (one person working one day is one person-day). Both appointments are made by you as the client; your designer or builder can take the role if they agree and are competent. Having one main contract does not remove the need to consider subcontractors.

Make each appointment at the start of the relevant stage and get written acceptance. Managing purchases and scheduling does not automatically make you a competent construction-stage supervisor. These roles are normally carried out by experienced designers or contractors. A competent main contractor can accept the PSCS role, but does not take it on automatically.

Notify the Health and Safety Authority (HSA) where the duration thresholds apply, cooperate with the supervisors and retain the safety file. See insurance when you project manage for construction-stage safety-plan checks.

Compare the full cost

Use the same drawings and specification to price both routes. Include:

• Trades and materials at current quoted prices.
• Contractor margin and overheads for the main-contract route. Ask for a breakdown rather than a total alone.
• Your time, including unpaid leave or reduced hours.
• Contingency, with a larger reserve when you coordinate trades yourself.
• Delay costs, including extra interest, rent or temporary housing.
• VAT, checked with your accountant. Invoices from unregistered tradespeople and from a contractor are treated differently, and labour and materials need separate consideration.

Ask a quantity surveyor for a fee proposal to compare the options and identify omitted work. If the apparent saving disappears after these costs, use that result in your decision rather than the initial trade totals.

Protect payments on either route

Agree scope, price and payment stages before work starts, even with someone you trust. Pay against completed, inspected work and avoid large deposits for materials you cannot see. Money paid ahead of the work is what you are most likely to lose if a builder goes bust or walks off the job.

Keep invoices, quotes and certificates in one folder. Agree which documents your lender, insurer and professionals require; keep the others as your project record. When a main contractor pays subcontractors, your own payment and certification obligations still come from the main contract.

Write down final-payment conditions and any retention. Holding back an agreed amount can help you get defects addressed, but follow the contract. Before withholding money for defective work, get advice on contractual and statutory remedies: the amount and notice can matter. See snagging a new build and choosing a builder and contract.

Choose the certification route before starting

Submit the commencement notice and required plans before work starts and name the builder on either route. Under normal statutory certification, the documents include the design certificate, assigned-certifier appointment and undertakings, builder undertaking and preliminary inspection plan. The completion certificate must be validated and registered before occupation.

An owner building a new single dwelling on a single-unit development may instead submit a Declaration of Intention to Opt Out of Statutory Certification with the commencement notice. With a valid declaration on the register, the statutory completion-certificate procedure does not apply.

Building Regulations compliance remains your responsibility. The opt-out does not waive planning, safety or lender requirements. Decide with your professionals and lender before starting. One lender, for example, still requires professional reports and a final compliance certificate for an opted-out build; check what your own offer requires.

If you hire trades directly, agree who collects electrical and other specialist certificates. A main contractor’s scope should state which documents they supply. See the build stages for the full sequence.

Would a project manager suit you better?

You can pay a project manager, or an architect administering the build, to run the programme and check quality while you control the money. Agree the fee, whether a fixed sum, day rate or percentage, and list the exact duties. Record whether they can instruct trades on your behalf.

Compare the fee and your remaining responsibilities with the main-contractor quote. A lower total is not guaranteed. You still hold the direct trade contracts unless agreed otherwise, so allow for gaps and overruns.

Another option is to hire a builder for the shell and manage the finishes yourself. Put the division of work, documents and responsibility in writing, rather than assuming the shell contract covers later trades.

Make the decision before committing

Ask yourself:

1. Can I give the build the hours it needs every week?
2. Do I have a trusted architect, engineer or experienced person to help identify problems?
3. Can I absorb a larger overrun than a fixed-price route might allow?
4. Would the saving be worth the stress if things went badly?

If most answers are no, a main contractor or paid project manager is likely to fit better. If most are yes, managing the build yourself may be realistic, subject to checking the budget, programme and safety appointments.

Whichever you choose, ask your lender and insurer in writing how the route affects their terms. Agree professional appointments, inspections and certification. Write down who is responsible for each task before signing contracts.

Allow time between trades: one late job can delay the next and leave you paying for idle workers. Check availability alongside references and insurance, rather than choosing the cheapest quote alone. Keep scope and decisions in writing so that neither you nor the builder has to rely on “I thought that was included” halfway through construction.