Managing a Building Project from Drawings to Completion

From Drawings to a Buildable Package

Good projects rarely go wrong on site; they go wrong in the weeks before anyone lifts a spade. Once your planning permission is through and building regulations approval is under way, the drawings need to become a package a contractor can actually price and build from. That means a full set of scaled plans, elevations and sections, a detailed specification of materials and finishes, and a schedule of works that breaks the job into stages.

If structural work is involved, you will also need engineer's calculations and details — steel beam sizes, padstone positions, lintel specifications. Your building control body will want to see these, and so will any competent builder. Ask your designer to include a finishes schedule and a clear list of exclusions so no one is guessing whether the £28,000 quote includes the kitchen or just the walls around it.

Appointing a Contractor Without Guesswork

Get at least three tenders on the same information, and give each contractor the identical pack. If one prices from a sketch and another from the full specification, you are not comparing like with like. Ask for a breakdown by stage rather than one lump sum, so you can see where the money sits.

Before you appoint, do the boring checks properly:

• Ask for two recent references from similar-sized extensions and actually ring them.
• Confirm public liability and employer's liability insurance, and ask for current certificates.
• Check whether they are VAT registered, and whether they use directly employed staff or subcontractors.
• Agree who is the principal designer and principal contractor for CDM purposes if the project is notifiable.

Put the appointment in writing. A JCT Minor Works contract or a Homeowner contract is the standard route for domestic extensions and gives both sides a clear framework for payment, variations and dispute resolution. Never rely on a verbal agreement and a handshake, however well you get on.

Setting Up on Site and Checking Progress

Before work starts, agree a programme with dates for each stage: demolition, foundations, drainage, superstructure, roof, first fix, plaster, second fix, decoration. Pin a copy to the site hoarding or the kitchen wall. It will change, but having it in writing makes slippage visible early rather than in month four.

Agree a payment schedule tied to completed stages, not to calendar dates. Typical milestones for an extension might be foundations signed off by building control, damp-proof course and oversite complete, roof watertight, plaster finished, and practical completion. Hold back a retention of 2.5 to 5 per cent until snagging is done — it is standard practice and a reasonable contractor will expect it.

Walk the site weekly with the contractor. Keep a simple site diary: date, weather, who was on site, what was done, any issues raised. Photograph everything, especially anything that will be covered up — drainage runs, insulation, steelwork, noggins for future fittings. These photos are gold if a question arises later.

Check the work matches the drawings as it progresses. A wall built 100mm off line is easy to fix on day one and expensive to fix after plastering. If your designer or a project manager is overseeing the job, make sure their site visits are scheduled and that they report back in writing.

Handling Variations Sensibly

Changes are the single biggest cause of budget overrun. Some are unavoidable — a drain discovered under the footprint, or a beam that needs a deeper section. Others are self-inflicted: deciding halfway through that you want bi-fold doors instead of sliders.

Set a clear rule from day one: no variation proceeds without a written price and your written approval. A quick text saying "go ahead" is not enough. Ask for the cost, the time impact and any knock-on effects, then confirm by email. Keep a running variations log with dates, descriptions and amounts, and reconcile it against the final account.

If you want to add work, expect it to be priced at the contractor's day rate or a fair quotation, and expect it to push the programme. Try to batch decisions — a single variation covering three items is easier to price than three separate ones.

Completion, Sign-Off and Snagging

Practical completion is the point at which the work is substantially finished and you can use the space, even if a few minor items remain. Before you agree it:

• Obtain the building control completion certificate — you will need it when you sell.
• Collect warranties, guarantees and any manufacturer certificates for boilers, glazing, roofing or render systems.
• Ask for the electrical installation certificate, gas safety record and any Part P notification.
• Get as-built drawings if the layout changed during the build.

Walk the property room by room and compile a snagging list — every scratch, sticking door, uneven tile and missed paint edge. Send it in writing and agree a deadline for completion, typically two to four weeks. Release the retention only when the snags are done and any defects that appear in the first few months have been put right.

Finally, confirm the final account in writing: original contract sum, agreed variations, retention released, and confirmation that no further sums are due. Keep every document together in one folder. A tidy paper trail is the difference between a project you remember fondly and one you would rather forget.