BuildTrue Estimating FAQ
Estimating questions tend to repeat because the traps repeat: a volume that looked right in the wrong unit, a waste allowance that was never added, a price built with markup when the plan assumed margin. This page answers the most common questions for Canadian contractors and serious DIYers in plain language, with the method behind each answer so you can apply it to your own measurements. For the calculations themselves, use the free BuildTrue calculators linked from the hub overview, and always verify local code and product instructions for the specific job in front of you.
How accurate does a construction estimate need to be?
It needs to be accurate enough that you order the right materials once and price the job without missing a whole category of cost. Early planning estimates can carry wider allowances because scope is still moving. An order quantity or a client bid needs tighter work: measured dimensions, base quantities shown separately from waste, consumables listed, and labour counted in hours. The standard to aim for is traceability. If someone else can follow your measurements and formulas and land on the same numbers, the estimate is doing its job, even if site conditions later require a documented change.
How much waste should I add to an estimate?
There is no single correct percent, and any source that gives one without asking about the job should be treated with caution. Simple, rectangular, well prepared work needs a smaller allowance. Cut heavy, irregular, or difficult access work needs a larger one. Choose an allowance that matches the complexity, write it as its own line beside the base quantity, and review it after the job against what you actually used. Over several jobs, your own records will calibrate the allowance better than a generic table, because they reflect your crew, your suppliers, and your typical work.
How do I convert cubic metres to cubic yards for a concrete order?
Multiply cubic metres by 1.30795 to get cubic yards. For example, 2.00 cubic metres times 1.30795 equals 2.6159 cubic yards, about 2.62 cubic yards. Work the whole takeoff in metric first, convert once at the ordering stage, and confirm which unit your supplier will use on the order and the delivery ticket. Most estimating unit errors happen when measurements in metres, millimetres, feet, and inches are mixed inside a single calculation, not during a single, careful final conversion.
Should I deduct doors and windows from drywall area?
It depends on the size of the opening and your consistency. A common approach is to leave a single standard door in the area calculation, because the sheet must still be cut around it and the offcut is rarely fully usable, while deducting large openings such as wide cased openings or full height glazing. Whichever approach you use, note it on the takeoff and apply it the same way across every room in the job. Document the choice rather than chasing a perfect rule, and let your waste allowance reflect how cut heavy the rooms actually are.
What is the difference between markup and margin?
Markup is a percent added to cost: price equals cost times one plus the markup rate. Margin is a percent of the final price: price equals total cost divided by one minus the margin rate. The same percent produces a lower price as a markup than as a margin, because the percent is applied to a different base. Confusing the two is a common reason a job that looked profitable on paper returns less than planned. Decide which method your business uses, label it on every bid calculation, and check the result by dividing profit by price to confirm the margin you intended.
Why does my bid need overhead if I already counted materials and labour?
Materials and direct labour are only the costs tied to that one job. Overhead covers the costs of running the business itself, such as insurance, vehicles, tools, licences, software, and administration, which continue whether or not a particular job is underway. If bids do not recover a share of overhead, those costs are paid out of margin, and the business earns less than the bid suggests, or loses money while staying busy. Apply overhead recovery as a separate, labelled step based on your own business figures, so you can see whether each job is carrying its share.
Bags or ready mix: which is better for a small concrete job?
Neither is automatically better. Bags suit very small volumes, tight access, and work that can be placed in stages, but mixing labour and time grow quickly with bag count. Ready mix suits larger volumes and single continuous placements, with plant batched consistency and truck pace placing, subject to the supplier delivery terms and site access. Compare total placed cost for your job: material, delivery terms, any pump needed, and the crew hours each method requires. Calculate the volume first, in cubic metres and as a bag count at the yield printed on the bag you would buy, and let that real comparison drive the choice.
How do I estimate labour hours without just guessing?
Break the job into tasks and estimate each one: preparation and protection, layout, installation, finishing, cleanup, disposal, and handling or travel where it applies. Consider crew size, access, height, and whether the space is occupied, and record hours per task rather than one total. After the job, compare actual hours to estimated hours task by task and note why they differed. That review loop, repeated across jobs, turns guessing into calibrated judgement. A single job will still surprise you sometimes, but the surprises get smaller and better understood.
Sources and figures note
Unit conversion used above: 1 cubic metre equals 1.30795 cubic yards. Material yields, fastening patterns, and coverage figures vary by product: check the manufacturer instructions for the products you buy. Building requirements are governed by the applicable provincial building code and local bylaws. Verify local code. This FAQ teaches estimating method only and is not financial or structural advice.