Before requesting a residential estimate, gather as much reliable project information as possible. An estimator can work with limited information, but the result will be based on more assumptions and may be less reliable than an estimate prepared from coordinated drawings and specifications.
Start with the right drawings
For most domestic extensions, refurbishments and new-build projects, provide the latest revision of the following drawings where they are available:
- Location plan: this shows the property in its surrounding area, including access and the application site.
- Site or block plan: this shows the building and proposed works in relation to the boundaries, access, adjacent streets and other structures on the site.
- Existing and proposed floor plans: these should identify rooms, walls, doors, windows, storeys and the area of new or altered accommodation.
- Existing and proposed elevations: these help define external appearance, openings, finishes, roof form and the relationship with boundaries.
- Roof plans: include these where the roof shape, covering, openings, chimneys or rooflights are changing.
- Sections and level drawings: these are particularly important where there are changes in ground levels, steps, retaining structures, split levels or sloping sites.
- Detail drawings: provide these for items such as stairs, built-in joinery, unusual interfaces, traditional features, specialist finishes or complex construction details.
Include specifications, not just dimensions
Drawings show geometry, but they do not always define the complete construction standard. Add a written specification, schedule or notes covering the materials and performance you expect. This might include:
- foundations, ground floor and upper floor construction;
- external walls, insulation, cladding, brickwork or render;
- roof structure, coverings, insulation and rainwater goods;
- windows, external doors, internal doors and ironmongery;
- kitchen, utility room and bathroom allowances or selected products;
- floor, wall and ceiling finishes;
- heating, ventilation, plumbing and electrical requirements;
- fire, acoustic, thermal and accessibility requirements identified by the design team;
- external works, landscaping, fencing, drainage and paving; and
- demolition, making good, temporary protection and reinstatement.
If a finish or product has not been selected, say so clearly. For example, “allow for a mid-range kitchen” is not the same instruction as a fixed schedule naming the units, worktops, appliances and installation requirements. The estimator can include an allowance, but the basis of that allowance should be visible.
Provide schedules and consultant information
Schedules reduce the risk of important items being missed. Useful schedules may include a window and door schedule, room finish schedule, sanitaryware schedule, kitchen schedule, ironmongery schedule, equipment schedule and landscaping schedule.
Also provide relevant reports and design information, such as a measured survey, structural engineer’s drawings, drainage proposals, arboricultural information, asbestos information, ground investigation, energy or sustainability requirements and any party wall or access constraints. Not every project needs every report. The point is to identify information that changes the construction method, risk, quantity or responsibility for the work.
Explain the site, access and existing building
A drawing set may not reveal all the conditions that affect cost. Give the estimator a short site information note covering:
- the property address and project description;
- how the site is accessed and whether vehicles, skips, scaffolding or deliveries are restricted;
- neighbouring properties, shared drives, narrow roads or limited working space;
- occupancy arrangements during the works;
- known drainage, utility or service constraints;
- existing defects, damp, movement or previous alterations;
- demolition and disposal requirements;
- working-hour restrictions or sensitive neighbours; and
- any known planning, conservation, leasehold, party wall or access matters requiring specialist advice.
Photographs, a site walk-round and a measured survey can be particularly helpful for refurbishment work. If the estimator has not inspected the property, state that clearly and identify which matters remain unverified.
Record the decisions that affect the price
Tell the estimator what you have decided and what remains open. Important decisions include the intended quality level, preferred materials, sanitaryware, kitchen, appliances, windows, doors, heating system, renewable technologies, decoration standard and external works.
Also confirm whether the estimate should include professional fees, surveys, statutory charges, utility connections, finance costs, VAT, contingency, client-supplied items and contractor preliminaries. These inclusions vary between projects, so they should be agreed rather than assumed.
Early budget estimate or detailed estimate?
An early budget estimate is appropriate when the design is still developing. It may be based on outline drawings, approximate floor areas, an initial specification and stated assumptions. Its purpose is to test affordability, compare design options or support an early decision. It should not be treated as a fixed construction price.
A more detailed estimate normally needs coordinated drawings, specifications, schedules and clearer site information. It can assess quantities and work sections in greater detail, but it remains dependent on the completeness and consistency of the information supplied. RICS states that effective cost prediction depends on a clear definition of scope, appropriate data, suitable skills and an appropriate system. Its professional standard also highlights the problems that can arise when accurate inputs are not available at the right time. Read the RICS cost prediction professional standard for the wider principles.
What happens when information is missing?
Missing information does not always prevent an estimate, but it changes its basis. An estimator may need to assume foundation conditions, construction build-ups, product quality, access arrangements, service routes, working hours or the extent of making good. Those assumptions can affect both the total and the confidence that can be placed in it.
A responsible estimate should identify qualifications, exclusions, provisional allowances and items requiring confirmation. Ask for the assumptions to be listed in plain English. If a major design decision changes later, the estimate should be reviewed rather than quietly compared with the original figure.
Where structural stability, ground conditions, hazardous materials, drainage, fire safety, planning compliance or building regulations are uncertain, obtain advice from the relevant qualified professional. An estimator can price defined work, but should not replace a structural engineer, building surveyor, architect, designer or statutory authority.
If you are unsure what level of estimate is right for your project, tell us about your project and we can suggest a practical next step.
Residential estimate preparation checklist
- Send the latest drawing issue and clearly mark superseded information.
- Include existing and proposed plans, elevations, sections and site information relevant to the work.
- Attach the written specification and all available schedules.
- List preferred products, finishes and quality standards, or state where allowances are required.
- Provide surveys, engineering information and reports that affect construction.
- Explain access, occupancy, restrictions, demolition and external works.
- Confirm whether VAT, fees, contingency, utilities and client-supplied items are included.
- State the purpose of the estimate and the level of detail expected.
- Ask for assumptions, exclusions, provisional allowances and unresolved information to be identified.
- Arrange a review when drawings or client decisions change.
The best time to request an estimate is when the project information is sufficiently clear for the estimator to understand the scope, but early enough for cost advice to influence decisions. If some information is not ready, send what you have, label the estimate as an early budget and ask which missing items would most improve its reliability.
