Home & property

Wall area minus the openings, divided by the coverage on the tin, times the number of coats, and it is the last one people get wrong. A second coat uses noticeably less than the first, because it is going onto paint rather than into a porous surface, so doubling the first-coat figure over-orders. Bare plaster goes the other way and drinks the mist coat. Ceilings are the other trap: people measure the walls carefully and then guess the ceiling, when it is usually the biggest single surface in the room.

Because a screen emits light and a wall reflects it, and no amount of clever software gets round that. Your monitor is making the colour out of red, green and blue light at whatever brightness and colour temperature it happens to be set to; the wall is bouncing back whatever your room lights give it, minus what the pigment absorbs. The same tin genuinely looks like two different colours in a north-facing room and a south-facing one. Any visualiser, ours included, is for narrowing the shortlist. The tester pot is the only thing that answers the question.

Usually not, and the number that decides it is two metres. Under permitted development you can generally put up a fence, wall or gate to two metres without applying, but that drops to one metre where it adjoins a highway used by vehicles, or a footpath beside one, which catches most front gardens. Listed buildings, conservation areas and properties with permitted development rights removed are all outside that, and so is anything that would block a required sightline. The height is measured from the ground on the higher side.

Source: Fences, gates and garden walls, Planning Portal

Completely, and converting the number rather than the container is how people end up short. America buys paint by the gallon, which is 3.785 litres, with the quart as the sample size. Britain and Australia sell 2.5 and 5 litre tins. So the American question is how many gallons, the British one is how many 5 litre tins, and the two do not divide into each other tidily. Coverage is quoted differently too, square feet per gallon against square metres per litre, so the tools here switch the unit and the container together rather than converting a British answer into American words.

Cut it into rectangles and add them up, which sounds obvious and is still the bit people skip. Almost every awkward room is a rectangle with something taken out of it or added on: a chimney breast, an alcove, an L, a bay. Measure the main box, then measure each lump separately and add or subtract. For anything genuinely curved, treat it as the rectangle that contains it and accept you are ordering a little over, because the offcut is cheaper than the second delivery. What you should not do is average two unequal walls, since that quietly loses area in one direction and gains it in the other.

Because carpet arrives on a roll of a fixed width and your room almost certainly is not that width. The roll decides everything: a room slightly wider than the roll needs a second drop and a seam, and the offcut from that drop is usually unusable. It is why a room that is barely bigger can cost noticeably more, and why turning the lay direction sometimes saves a whole strip. The calculator here tries both orientations and tells you which wastes less, because the cheaper answer is often the one that looks wrong on paper.

Not a letter band. NatHERS, the Nationwide House Energy Rating Scheme, is run on behalf of every state and territory government and has been going for more than three decades. It is how a new home shows it meets the energy efficiency requirements of the National Construction Code, and around nine in ten new homes use it to do that. Two things catch people out. It is now presented publicly as Home Energy Rating, so anything written before the rebrand calls it the older name. And disclosure when a home is sold is set state by state rather than nationally, so it is not the automatic requirement a British EPC is.

Source: Nationwide House Energy Rating Scheme

Both, depending on who is talking, and it is not a mistake. A Canadian estate agent quotes square feet, because that is what buyers picture, while the building code, the drawings and the energy rating are all metric. So a house is advertised at 1,800 square feet and built to a code written in millimetres, and both numbers are correct. The practical effect for anybody ordering materials is that the listing and the plan will not use the same units, and converting the listing is the wrong direction: work from the plan.

Longer than people wait, and the tin is the authority rather than the clock. Emulsion is usually touch dry quickly and ready to recoat in a couple of hours; oil-based takes much longer, sometimes overnight. What moves both is temperature and humidity, so a cold room in November is not the same job as the same room in June, and a bathroom is slower again. Recoating too early is the commonest cause of a finish that looks patchy or drags: the roller lifts the coat underneath instead of covering it, and no amount of extra paint fixes it afterwards.

No, and the two answer completely different questions. Everything here works from dimensions you supply, so it can tell you how much of something you need and roughly what a job involves. A survey tells you what is actually there: what the wall is built of, whether the damp is rising or falling, what is under the floor, whether the thing you want to remove is holding something up. No tool can know any of that from a number you typed. What these are genuinely for is walking into that conversation knowing what to ask, and not paying somebody to measure a room you could have measured yourself.