Structure & materials

If anything you are doing changes what the building carries, yes, and nothing on this hub is a substitute for one. What these tools are for is walking into that conversation knowing what you are asking, which is worth real money because an engineer charges for the time it takes to work out what you meant. Turn up with a span, a load and a dimension and you get an answer. Turn up with "can I take this wall out" and you pay for the survey that establishes what the wall is.

It depends on the tool, and the page says so rather than leaving you to guess. Britain is Building Regulations with Approved Documents. America is the International Residential Code and International Building Code, adopted and amended state by state, so "the code" is really the version your own state adopted. Australia is the National Construction Code, which contains the Building Code of Australia. Canada is the National Building Code of Canada, adopted provincially. Quantities are arithmetic and are the same everywhere; anything that reports a limit or a size names the code it came from.

Sources: Approved Documents, gov.ukNational Construction Code

Because they are the same board and the two words are not close to equal in search. Drywall is searched roughly forty times as often as plasterboard across America and Canada, and Britain is the only market that says plasterboard at all. Rather than pick one and lose the other half of the audience, the calculator carries both names and the tool switches its sheet sizes with them: a British board is 1200 x 2400mm, an American sheet is 4 x 8 feet, and those are not the same number of boards for the same wall.

On the tools where it changes the answer, yes, and the switch converts what you already typed rather than reinterpreting it, so flipping the unit never silently changes the size of your room. Where you will still meet metric is anything quoting a British or Australian standard, because the figure in the standard is metric and rounding it to inches would be inventing a number the standard does not contain. Those pages convert the result rather than the rule.

Because we cannot read one without paying, and we will not guess. The span tables live in the International Residential Code, which is ICC copyright, and the only free access is behind an account, which breaks the promise at the top of every page on this site. Where a US federal lab has already republished a code table for its own guidance, we use that and cite it, which is how the insulation R-value tool exists. For spans, nobody has, so there is no tool rather than a tool full of numbers somebody half remembered.

Source: ICC Digital Codes, and the account gate

It appears on every tool that outputs a size or a capacity rather than a quantity, and it says what the number is and what it is not. A quantity tool tells you how much to order and being wrong costs you a second delivery. A sizing tool tells you what will hold something up, and being wrong costs considerably more, so those pages say plainly that the output is for scoping and pricing and that somebody qualified signs the actual design. The note is automatic rather than a judgement call per page, which is why it reads the same everywhere.

Work out the volume first, then divide, and the second step is where people go wrong: a bag yields far less finished concrete than its own weight suggests, because the dry mix loses volume once it is wet and compacted. The volume calculator here does the first half and the mix page does the second. The other thing to add before you order is waste, and on a slab poured onto ground rather than into formwork the ground itself takes more than you would expect.

No, and that is exactly why the brick calculator claims Britain, America and Canada but not Australia. A standard Australian brick is 230 x 110 x 76mm against a British 215 x 102.5 x 65mm, which changes both the number per square metre and the coursing, so running Australian work through British figures is wrong by enough to matter on a delivery. The reason it is not simply built is the same one that stops the American span tables: the dimensional standard is AS/NZS 4455, Standards Australia sells it, and nothing on this site is built on a figure we had to buy or guess. Badging the tool for a market it would get wrong is worse than leaving the market off.

Source: Think Brick Australia, technical FAQs

Because the country converted and the lumber trade did not. Canada builds to a metric code and prices fuel and distance in metric, but a stud is still a two by four and a sheet is still four by eight, and those are nominal imperial names for pieces that are actually 38 x 89mm and 1220 x 2440mm. So a Canadian job routinely mixes a metric drawing with an imperial materials list, which is not a mistake and does not need correcting. The tools here follow the same split rather than forcing everything into one system.

Source: Lumber, Canadian Wood Council

Not the steel, most of the time. The section itself is sold by weight at a rate that moves slowly, and on a domestic job it is usually the smaller half of the bill. What moves the number is everything around it: the padstones or columns it lands on, getting it into a building that already exists, whether it needs craning or can go in by hand, the fire protection, and the engineer and building control behind all of it. A beam that is cheap to buy and awkward to install costs more than a heavier one that walks in through a doorway.