How to Get an Early Construction Cost Estimate Before Your Design Is Finished
One of the most common misconceptions about quantity surveyors is that you need a complete set of architectural drawings before you can get a meaningful cost figure. In reality, some of the most valuable cost advice a QS provides happens long before the design is finished, sometimes before it has even properly started.
If you have a project in mind, a rough sketch, a concept plan or even just a clear idea of what you want to build, it is not too early to get an independent cost assessment. This post explains how early stage cost advice works, what it can and can't tell you, and what you need to provide to get a useful number.
Why Early Construction Cost Estimate Advice Matters
The earlier in the design process you get independent cost advice, the more value it delivers. This might seem counterintuitive. Surely a more complete design produces a more accurate estimate? That's true, but accuracy and usefulness are not the same thing.
A detailed pre-tender estimate prepared from fully documented drawings is highly accurate, but by that stage the design is locked in and the budget impact of any changes is significant. Redesigning a documented set of drawings because the tender comes back over budget is expensive and demoralising, and it's a situation that could have been avoided with earlier cost input.
Early cost advice, by contrast, gives you the information you need when it still has the power to influence decisions. Should the house be single or double storey? Should the basement be included or deferred? Is the proposed specification level realistic for the available budget? These are design-stage decisions that carry major cost implications, and they are best made with an independent cost view in hand rather than on gut feel or a builder's rough estimate.
What "Minimal Information" Actually Means
Early stage cost estimates can be prepared from a surprisingly limited amount of information. Depending on where the project is up to, this might include:
A project brief only
If you know the type of building, the approximate floor area, the location, and the intended specification level, a preliminary feasibility estimate can be prepared from that information alone. This is the highest-level estimate, often called an order of magnitude estimate, and is used to establish whether a project is broadly feasible before design costs are committed.
A sketch or hand-drawn concept
Even a rough sketch that conveys the general layout, the number of storeys, and the approximate footprint provides enough information to prepare a concept estimate with more confidence than a brief alone. The key inputs at this stage are floor area, general construction type, and site conditions.
Concept plans with sections and elevations
This is the most common scenario for early cost enquiries. An architect or designer has produced concept drawings showing the layout, form, and general intent of the design, but the documentation is nowhere near complete. This level of information is more than sufficient to prepare a concept estimate that gives a realistic indication of the cost range for the project.
A set of DA drawings
DA documentation is generally the point at which an estimate moves from concept level to a more structured cost plan, with elemental cost breakdowns across structure, envelope, finishes, services, and external works. This is also typically the stage at which a formal council cost report is required.
What the Estimate Can and Can't Tell You
Honesty about accuracy at early stages is important. A concept estimate prepared from minimal information is not the same as a pre-tender estimate prepared from full documentation. The difference is in the range of uncertainty around the figure.
As a general guide, accuracy at each stage is broadly as follows:
Order of magnitude estimate (brief only): plus or minus 25 to 30 per cent
Concept estimate (sketch or concept plans): plus or minus 15 to 25 per cent
Preliminary estimate (concept plans with sections and elevations): plus or minus 10 to 15 per cent
Design development estimate (advanced documentation): plus or minus 5 to 10 per cent
Pre-tender estimate (full documentation): plus or minus 5 per cent
An order of magnitude or concept estimate with a 20 per cent range on a $1.5 million project means the actual cost could reasonably land anywhere between $1.2 million and $1.8 million. That's a wide band, but it's still enormously useful information. It tells you whether the project is in the right financial territory, whether the budget needs to be reconsidered, and whether there are aspects of the brief or design that need to be reined in before further design investment is made.
What it doesn't do is give you a number precise enough to sign a contract against. That level of precision requires full documentation, and attempting to use a concept estimate as a contract figure is one of the more common causes of budget blowouts in residential construction.
How a QS Builds an Early Estimate
When design information is limited, a quantity surveyor draws on a combination of benchmarked data and professional judgement to arrive at a cost figure.
Benchmarking involves applying known cost data from comparable completed projects, adjusted for differences in location, specification level, site conditions, and current market rates. For a Sydney residential project, this means drawing on cost data from similar homes built in comparable suburbs, adjusted for current labour and material costs and the specific characteristics of the proposed design.
Where design information exists, even at a concept level, elemental cost planning is used to structure the estimate around the main cost components of the building: substructure, superstructure, roof, external walls, internal walls and finishes, wet areas, services, preliminaries and external works. Each element is assessed based on the available information and priced at a rate appropriate to the specification level intended.
Where information is missing, the QS makes clearly stated assumptions. A good early estimate doesn't pretend certainty it doesn't have. It documents what has been assumed, flags the areas of greatest cost uncertainty, and identifies what additional information would improve confidence in the figure.
What You Need to Provide
To get a useful early stage cost estimate, you don't need much. The more you can provide the better, but a meaningful assessment is possible from:
The project address or suburb
A description of what you want to build, including approximate size and number of storeys
Any drawings, sketches, or concept plans available, even rough ones
An indication of the intended specification level, whether standard, mid-range, or premium
Any known site constraints such as slope, access limitations, heritage overlay, or bushfire attack level
That's genuinely enough to get started. If you have more, provide it. If you only have a sketch on a napkin and a clear idea of what you want, that's a starting point too.
Is an Early Estimate Worth the Cost?
For most projects, yes, and often substantially. The fee for an early stage concept estimate is modest relative to the design fees, approval costs, and construction costs that follow. If the estimate reveals that the project as conceived is over budget, that information is worth far more than the cost of the estimate, because it allows the design to be recalibrated before significant resources have been committed.
The alternative, discovering at tender stage that the project exceeds the budget by 30 per cent, means either funding the shortfall, redesigning at significant cost, or abandoning the project altogether. None of those outcomes is cheap, and all of them could have been avoided with early independent cost advice.
Get an Early Cost Assessment for Your Project
CPP Quantity Surveyors provides early stage feasibility and concept cost estimates for residential and small commercial projects across Sydney and Regional NSW. If you have a project in mind and want an independent cost view before committing to further design work, contact us to discuss what you have and what we can do with it. A meaningful assessment is often possible from less information than you think.
By Gary Uys, FAIQS CQS, Director - CPP Quantity Surveyors
📞 (02) 9629 3495
