Building & Construction Tools
Framing, concrete and masonry layout, with the geometry the rules of thumb quietly get wrong.
Common, hip, valley and jack rafter lengths from a pitch — plus why a hip sits at a shallower angle than the common on the same roof.
Concrete Volume & Bag CalculatorCubic yards and bag counts for slabs, footings, piers and steps — and whether the pour can be finished before the concrete starts setting.
Stair Stringer CalculatorRiser, tread and stringer layout with code checks — including the bottom cut that makes the difference between an even flight and a violation.
Rebar Spacing, Quantity & Lap SpliceBar counts, weight and ACI lap splice lengths for a slab — plus the height the steel has to sit at, which is where most reinforcement fails.
Joist Span CalculatorMaximum joist spans by species, size and spacing — with which limit actually governs, and the notching and boring rules for what comes after.
Header Size CalculatorHeader sizes for an opening, with jack studs and bearing — and why the plywood in a sandwich header is a spacer rather than a structural member.
Deck Framing CalculatorJoists, beams, footings and board counts for a deck — and the load each ledger fastener carries, which is where decks actually fail.
Stud & Wall Framing LayoutStud counts, layout marks and materials for a wall — starting with why the first mark goes at 15¼ inches rather than 16.
Handrail & Baluster SpacingBaluster counts and gaps for guards and stairs — with the three different sphere rules, and why thinner balusters need more of them.
Sheathing & Plywood Cut OptimizerSheet counts and cut layouts for 4×8 sheathing, with offcuts reused — because rows times columns overstates the order.
Rough Opening CalculatorRough openings and framing for windows and doors, with the egress check — where meeting both minimums still fails the code.
Trim & Crown Molding CalculatorLinear feet for trim plus crown compound miter and bevel angles — where neither number is 45 and the profile name misleads you.
Shelf Span & Cabinet LayoutShelf sag and maximum spans, 32mm pin spacing and door sizing — with the levers ranked by how much they actually do.
Wall Square & 3-4-5 DiagonalDiagonals for squaring a layout, and why the 3-4-5 triangle everyone uses is far too small to square a real wall.
Concrete Mix Ratio & PSI GuideMix ratios, water-cement ratios and required strengths — and why one extra gallon of water per bag costs a fifth of the strength.
Control & Expansion Joint SpacingControl joint spacing for a slab, with the panel-shape rule that governs narrow slabs — and why you probably need no expansion joints.
Block, Brick & Mortar QuantityBlock and brick counts, courses and mortar bags — and why the nominal size already contains the joint, which is what makes it all divide neatly.
Retaining Wall Block & BaseBlock, base and drainage quantities for a segmental retaining wall — and the two facts that decide whether it stands up.
Paver Quantity, Base & SandPaver counts, base aggregate, bedding and joint sand — and why the sand is a bedding layer rather than a levelling one.
Concrete Crack DiagnoserRead a crack in concrete and pick a repair that holds — starting with why orientation matters more than width.
About these building & construction tools
Almost every rule of thumb in framing is a simplification of something that is cubed, and that is where they break. Stiffness rises with the CUBE of a member depth and only linearly with its width, which is why one deeper joist normally beats two shallow ones — but nominal lumber sizes are not evenly ratioed, and the gaps close as they get bigger. A 2x8 is 32 per cent deeper than a 2x6 and a 2x10 is 28 per cent deeper than a 2x8, so going deeper wins both times. A 2x12 is only 22 per cent deeper than a 2x10, and doubling up wins there instead. The crossover sits exactly at the cube root of two, a depth ratio of 1.26, because a second ply always buys precisely twice the stiffness and nothing more. The same cubing explains why the plywood in a sandwich header does nothing: two 2x plies make three inches, a 2x4 wall is three and a half, and the half inch of plywood is there to close that gap so the header finishes flush. Credit it generously as though it were graded lumber and it adds one sixth, against 80 to 129 per cent for one size deeper. Geometry catches people out in the other direction too. A hip rafter sits at a SHALLOWER angle than the common rafter on the same roof, because it crosses the corner diagonally and travels 1.41 times as far horizontally to reach the same ridge height — 19.5 degrees against 26.6 on a 6/12 roof, which is the entire reason a framing square has a 17 printed on it. And the arithmetic that ruins most concrete orders is simply that slab thickness is quoted in inches while everything else is in feet, so four inches is a third of a foot rather than four. What these tools try to do is show which constraint is actually binding, since that is what tells you what to change: the limit on a bagged concrete pour is not how many bags you can carry but whether you can place it before it sets, and the limit on a stair is not the stringer but the three eighths of an inch the code allows between the tallest riser and the shortest. Everything here is layout and quantity rather than structural design. Span tables, local codes and, past a point, an engineer are what settle whether something is safe to build.