One Line Moved on a Drawing
The kitchen layout needed another 800 mm of run, so the door slid 800 mm along the wall. On the drawing that is a line moved. On the wall it is a lintel whose new bearing lands within a brick of a chased-out service run, a switch drop that now sits inside the opening, and a radiator whose tails come up in the exact spot the latch jamb wants. Mark both jambs on the wall before agreeing to the change, not one: the first mark tells you the door fits, the second mark finds the obstruction.
It helps to stop thinking of a doorway as a component and start treating it as three problems that happen to share a name. There is a hole in a wall that has to keep carrying whatever the wall was carrying. There is a frame inside that hole holding a leaf plumb enough to latch and stay where it is put. And there is floor on both faces of the wall that has to stay clear enough and flat enough for a person to work the door. Those three are sized in different orders, governed by different documents, and they fail independently of each other.
The order that keeps you out of trouble runs inward first and then back out. Start at the leaf, because everything dimensional is stacked on it. Build the frame around the leaf, the rough opening around the frame, and the structure around the opening. Then step outside the wall and check what you have done to the floor on each side, which is the check that gets skipped and the one that costs a rebuild. Renovation inserts a step nobody has on new build: the wall is already there, already loaded, and already full of things somebody else installed.
Clear Width Is Not Leaf Width
A 32 in door is a name. The dimension that matters is the clear width through the opening with the leaf swung to ninety degrees, measured from the face of the door to the stop on the opposite jamb, and the 2010 ADA Standards for Accessible Design set that floor at 32 in in section 404.2.3. Everything physical in the opening subtracts from it. The leaf gives back its own thickness once it is standing in the way. The stop takes a bite off the far side. A lever, a panic device, a projecting closer arm or a heavy weatherseal all take more, and they take it from the narrowest part of the route rather than from anywhere convenient.
This is why a leaf whose name matches the required clear width never delivers it. On a tight existing opening the usual moves are hardware rather than carpentry: swing-clear or offset hinges that carry the leaf out of the reveal when it opens, a flush pull instead of a lever on the trailing face, a surface closer relocated to the other side of the door. Each buys back a fraction of an inch that a wider leaf would have bought at the price of a wider hole, and in a renovation the hole is the expensive part.
The number itself travels badly. Approved Document M in England, BS 8300-2 for buildings beyond dwellings, AS 1428.1 in Australia, NZS 4121 in New Zealand, and ISO 21542 internationally each set their own effective clear widths, and several of them vary that width with the width of the corridor the user approaches along, which the ADA table does not do. Carrying a remembered figure from one jurisdiction into a job governed by another is a specific and common way to fail an inspection while being certain you were right. Find out which document has been adopted and amended locally before you commit a leaf size.
Existing buildings rarely offer the choice cleanly. A Victorian terrace with 686 mm openings will not yield 815 mm of clear width without moving masonry, and an honest early conversation about which doors on the route can realistically be widened is worth more to the client than a schedule that quietly assumes all of them can. Measure the leaves and the frames you already have before ordering anything: reused leaves are almost never the nominal size stamped on the schedule, and an out-of-production frame section changes the whole width chain below.
| Dimension | Measured between | Set by |
|---|---|---|
| Clear opening width | The face of the leaf at ninety degrees and the stop on the opposite jamb | The accessibility standard adopted where the job is |
| Leaf width | The two vertical edges of the door itself | The door schedule, and what the supplier actually stocks |
| Frame outside width | The outer faces of both jambs, over any casing leg the section includes | The frame manufacturer's profile drawing |
| Rough opening width | The inner faces of the two jack studs, or the finished masonry reveals | Frame width plus a shim space each side plus an out-of-square allowance |
| Structural opening | The bearing points of the lintel or header, past both reveals | The end bearing the lintel needs, which the door does not influence at all |
The Chain From Leaf to Rough Opening
Width is an additive chain and a forgiving one: an opening framed a little generous costs a wider shim stack and nothing else. Height is additive and unforgiving, because everything you place under the frame pushes it upward into a head that is already fixed. A moulded sill pan lifts the unit by its own thickness. A tapered packer under that pan, put there so water drains outward instead of standing, lifts it again. A floor build-up that changed between design and delivery lifts it a third time. All three come out of the same clearance at the head, and the head gap is the only part of the chain you cannot recover once the header is nailed off.
Head clearance is deliberately larger than the jamb shim space, and not because the trade is being cautious. The header above will deflect under load, a timber frame will shrink as it dries, and a heavy leaf on a wide opening earns a bigger allowance from most manufacturers for exactly those reasons. Squeezing it because the pan came in thicker than scheduled produces a door that binds at the head the first season the structure moves, and by then the casing, the finishes and the decorator have all been over it.
Where the unit maker publishes a rough opening, use theirs and stop calculating: it already contains their shim requirement and it is the dimension the warranty is written against. Reconstruct it yourself when you have a unit size and an installation detail but no published opening, or when a pan and packer under the sill mean the published figure no longer describes what you are building. For exterior doors that installation practice is set out in ASTM E2112, Standard Practice for Installation of Exterior Windows, Doors and Skylights, and the unit's own declared size and instructions are written against AAMA/WDMA/CSA 101/I.S.2/A440, the North American Fenestration Standard.
The height chain, header down to floor
- Header or lintel, with cripples over — sized for what the wall carries rather than for the door under it, and it needs bearing past the reveal at both ends Masonry Lintel Bearing Length Checker
- Head clearance and its packers — the only slack in the whole height chain, and every millimetre of pan and packer under the sill is taken out of it Fenestration Rough Opening Calculator
- Frame, stop and the leaf hung in it — clear width is read to the face of the open leaf and the far stop, never between the two jambs ADA Door Maneuvering Clearance Calculator
- Threshold pan with its upstands — cannot be retro-fitted under a hung door, so it is built before the leaf arrives or it is not built at all Window Opening Flashing Membrane Calculator
- Two finished floors over one subfloor — the level difference under the leaf is a change in level in the accessibility standards, not a trim detail Floor Transition Strip Calculator
Add the chain up before the jacks are cut: unit size, a shim space at each jamb, the head clearance, the pan and whatever is packed under it, plus something for an opening that will not be perfectly true.
Overall outside frame width of the window or door unit.
Overall outside frame height of the unit, sill to head.
The clear gap the manufacturer requires at each jamb.
The clear space required above the head of the unit.
Thickness of the pan the unit will sit on at the sill.
Any packer, sloped bevel or sub-sill placed under the pan.
Extra carried for a rough opening that will not be perfectly true.
Rough opening width
35.99 in
- Rough opening height
- 48 in
- Shim stack at each jamb
- 0.37 in
- Clear space at the head
- 0.5 in
- Build-up under the sill
- 0.25 in
- Rough opening area
- 12 ft²
They open the calculator with your figures already in it
Fenestration Rough Opening Calculator: 35.99 in — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 35.99 in — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- The manufacturer's installation instructions govern. Where they state a rough opening directly, use theirs rather than this reconstruction of it.
- Structural clearance under a header that will deflect, and any allowance for frame shrinkage, are design decisions this sum does not make.
Taking the Load Before Taking the Wall
New build gets to frame the opening while the wall is a stack of loose studs. Renovation does not. Before a saw touches an existing wall, settle what is standing on the line you are about to cut: joists bearing on it, a roof structure it has been propping since it was built, or masonry above that has quietly arched over the last opening and will stop doing so when you disturb its abutments. Settle what is buried in it too. A cable, a gas run or a hot-water pipe found with a reciprocating saw turns a doorway into an incident, and existing walls in older stock may also need a refurbishment survey for hazardous materials before any of it is opened.
Support is temporary works, and it is a designed item rather than a judgement call. In the UK that discipline sits under BS 5975, Code of practice for temporary works procedures and the permissible stress design of falsework, and the same logic applies wherever you are: somebody names the loads, somebody sizes the needles and props, and somebody checks what the props are standing on. That last one catches people out on upper floors, where a prop lands on a boarded floor that is itself spanning and needs a sole plate to spread the point load across more than one joist.
Needle spacing decides everything above it. Too few needles and the masonry between them has to span further than a bed joint will carry, so it drops out in a wedge while everyone watches. Cut needle holes rather than hammering them through, keep them tight to the underside of the course you are supporting, and pack the needle up to the masonry so it is taking load before the wall below it is removed rather than after. Nothing above should be able to move before the props are tight.
The permanent support goes back in with its own arithmetic. A masonry lintel to BS EN 845-2, Specification for ancillary components for masonry — Lintels, arrives with a manufacturer's bearing requirement and often a padstone requirement with it. A timber header is sized from the adopted code's span tables or by an engineer where the span or the load falls outside them. Either way the end bearing is measured past the reveal at both ends, on sound material, and the props stay in until the lintel is bedded and whatever it is bedded in has gained strength. Striking props early is how a perfect opening acquires a crack that runs diagonally away from one corner.
Work out what each needle and each prop is actually carrying, and how much sole plate has to sit under the prop, before anybody cuts the first hole through the wall.
From the head of the new opening up to the top of the wall, or to the next support.
The thickness of the masonry being held, excluding any leaf that is not being supported.
The bulk unit weight of the wall being held, mortar included.
The clear width of the opening being formed under the supported wall.
Centre-to-centre spacing of the needles through the wall.
The combined permanent and imposed load of any floor framing into this wall.
How much floor this wall carries — normally half the span of the floor either side of it.
What the surface the props stand on can take without settling or punching through.
Load carried by each needle
3.63 kips
Needling and propping is temporary works. This gives the loads to design to; it does not select the props, check them for buckling at their extended length, or confirm that what the props stand on can take them. All three belong to a temporary works designer.
- Load carried by each prop
- 1.81 kips
- Needles across the opening
- 4 needles
- Combined line load along the wall
- 1,208.77 lbf/ft
- Masonry share of that line load
- 707.52 lbf/ft
- Floor share of that line load
- 501.25 lbf/ft
- Sole plate bearing area required beneath each prop
- 0.87 ft²
They open the calculator with your figures already in it
Needle and Prop Load Calculator (Temporary Masonry Support): 3.63 kips — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 3.63 kips — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- Takes the full rectangle of masonry above the opening. That is deliberately conservative — arching can carry some of it away, but only in sound masonry with enough height and no nearby opening.
- Does not check the prop itself. A prop's safe working load falls sharply with extension and with any eccentricity at the head, and the manufacturer's chart is the only place that answer lives.
- Does not check the needle. Bending, shear and bearing on the masonry at the needle hole all need sizing against the load this page gives.
- Assumes props each side of the wall share equally. A single-sided scheme, or props at different extensions, does not.
Hanging It Plumb in a Wall That Is Not
Old walls lean, and you cannot plumb a frame to gravity and to the wall at the same time. Pick gravity. A hinge jamb that is out of plumb builds a door that swings itself open or drifts shut all day, and no adjustment to the strike will settle it. Plumb the hinge jamb in both planes first, then set the strike jamb parallel to the leaf rather than to the wall, and let the architrave or casing absorb the difference between the frame and the plaster. A tapered reveal that nobody notices is a better outcome than a door that will not stay where it is left.
Everything after that is bearing. Shims belong at the fastener positions and nowhere else, tight enough that the jamb cannot draw in when the screw is pulled home, and the hinge-side fixings need to be long enough to reach solid framing or a properly plugged reveal rather than stopping in the lining. Check both diagonals before the last fastener goes in, because a frame racked by two millimetres reads as a latch that catches on one corner and a gap that opens at the top of the leaf. It is a two-minute fix at this stage and a half-day fix once the casing is on and painted.
- Set the hinge jamb plumb in both planes and fix it at the top hinge only.
- Hang the leaf on that jamb and let it tell you whether it drifts before anything else is fixed.
- Fix the hinge jamb at the remaining hinge positions, shimming tight at each one.
- Set the head level and the strike jamb parallel to the closed leaf, holding an even margin all round.
- Pull both diagonals and correct before the final fixings go in.
- Work the latch and the closer through full travel, then fix off and pack the remaining voids.
The Landing Belongs to the Doorway
A doorway that is dimensionally perfect can still be unusable, and the reason is almost always floor. The 2010 ADA Standards deal with this in section 404.2.4.1 and its table, which sets the clear space a manual swinging door needs in front of it — and that space is not one number. It changes with the direction the user arrives from, with whether they are on the push side or the pull side, and on some cases with whether the door carries both a closer and a latch. The pull side always asks for more, because the user has to reach past the leaf, draw it toward themselves and then travel around the arc it sweeps before going through.
Approach direction is decided by the geometry you build, not by the drawing's intent. A door reached along a wall is a latch-side or hinge-side approach whatever the plan shows, and those cases demand space alongside the opening as well as in front of it. Both faces need checking separately: a landing that works for somebody leaving the room can fail for somebody arriving at it, and in a renovation the two faces frequently belong to different rooms with different constraints and different trades.
The floor of that space has to be level, within a slope of 1:48 in any direction under section 404.2.4.4, which is a drainage fall rather than a usable gradient. Renovation supplies endless ways to break this quietly. The landing turns out to be the top tread of a stair. It falls toward a floor gully somebody added. It is where the new floor build-up feathers out to meet the old. Or the door has been moved to a position where its own maneuvering space now overlaps the swing of the door opposite. None of these show on a plan at 1:100, and all of them are cheap to fix before the frame goes in.
Alteration work can also pull the requirement in from outside the room. Under the Department of Justice title III regulation at 28 CFR 36.403, altering an area containing a primary function carries an obligation to make the path of travel to that area accessible, within a proportionality limit, and the International Existing Building Code addresses the same ground where it has been adopted. A door being relocated inside a refurbishment is frequently on that path of travel, which turns the landing from a courtesy into a requirement someone will eventually measure.
Run the approach direction, the side of the door and the hardware fitted through the table before the frame position is fixed, and run it once for each face of the door rather than once for the doorway.
The direction someone arrives at the door from in a wheelchair.
Whether the door swings toward the person or away from them.
Whether the door has a self-closing device.
Whether the door has a latch that must be released to open it.
The clear width through the doorway with the door open ninety degrees.
Required clear depth at the door
60 in
The clear opening entered is at or above the 32 in minimum. The space alongside is measured beyond the latch side for front and latch approaches; for a hinge-side approach, check the figure in 404.2.4.1 for which jamb it is taken from before setting out. The maneuvering space must be level, within a slope of 1:48 in any direction, and must be clear of the door's own swing. Matching the figures quoted is not compliance. The rest of the requirement, and the installed work, are outside what this page can see.
- Clear space required alongside the doorway
- 18 in
- Total clear width of the maneuvering space
- 50 in
- Minimum clear opening width at the door
- 32 in
They open the calculator with your figures already in it
ADA Door Maneuvering Clearance Calculator: 60 in — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 60 in — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- Manual swinging doors and gates only. Sliding, folding, automatic and power-assisted doors are covered by different provisions, and doorways without doors different again.
- Does not cover doors in series, recessed doors, or the additional clearance a recess deeper than 8 in (203 mm) imposes on the approach.
- Says nothing about opening force, closing speed or hardware operability, which are separate requirements a compliant landing does not satisfy on its own.
Two Floors Meeting Under One Leaf
Under the leaf, two floor build-ups meet, and after a renovation they are rarely the same height. Engineered board on one side, tile on a decoupling mat on the other, and the doorway becomes a change in level. The 2010 ADA Standards treat that on its own terms: section 404.2.5 limits a threshold at a doorway, and the changes-in-level provisions in section 303 allow a small vertical step and require anything above it to be beveled rather than left square. Deciding this once, on paper, before either floor is laid is far cheaper than discovering it when the tiler has finished and the door will not close.
The undercut is the other half of the same decision, and it is usually being made for a different reason. Return air needs a path back to the plant in a house with central heating or cooling, and the gap under the door is how most dwellings provide it. But the leaf is bought to a length, the floor arrives later, and a door ordered against the old floor level fouls a new one by the thickness of the new finish. Fix the finished floor level at the opening before the door schedule is released, and where a leaf has to be trimmed check what the manufacturer permits — a fire door and most engineered leaves have a stated limit on how much can come off the bottom rail.
Then there is the strip itself, and this is a takeoff item rather than a detail. Every doorway and every material change on the job takes a transition, cut to the opening width with an allowance for trimming, and on a refurbishment of any size the count runs well past what anyone carries in their head. Choose the profile to suit the level difference before ordering: a flat strip, a ramped strip and a square-edge strip are not interchangeable once one floor stands proud of the other.
Count every doorway and every material change on the job at once, with an allowance for the cuts, rather than ordering strip a room at a time and running short on the last two openings.
SettingsSettings for this calculation
Waste is set to 5% by hand. Pick a tier above to replace it, or keep your own figure.
How many doorways or flooring-material changes need a transition strip.
The typical width of each doorway or transition opening.
Extra material for cuts and fitting at each transition.
Transition strip needed
15.75 ft
They open the calculator with your figures already in it
Floor Transition Strip Calculator: 15.75 ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- Every transition is measured from the single Average Opening Width figure, so a job that mixes standard 0.9 m (3 ft) doorways with one wide archway comes out short, and the field itself stops at 1.5 m (5 ft) — narrower than a set of double or sliding doors, which have to be entered as their own separate run.
- The opening width is treated as the finished strip length, with nothing added for a strip that overruns the jambs, tucks under the door stop, or turns a corner where the material change runs L-shaped into the room.
- Waste is one flat percentage applied to the whole total rather than to each opening, and it caps at 15% — at the default 5% across five doorways that is around 22 cm (8.5 in) of spare material for the entire job, not a guaranteed second attempt at any one threshold.
- The answer is a single continuous length in metres with no piece count derived from it, so a 4.73 m (16 ft) total still usually means buying a strip per doorway rather than splitting 4.73 m (16 ft) of stock between them.
- Fixing hardware falls outside the arithmetic entirely: the screw-down track or channel that two-part strips clip into, the plugs and screws, and any adhesive all have to be quantified separately from the linear length shown here.
Giving the Wall Back What the Hole Took
A wall does more than stand up, and cutting a doorway through it removes whichever of those jobs the wall was doing. If the wall was fire rated, the opening now needs a rated assembly, and NFPA 80, Standard for Fire Doors and Other Opening Protectives, governs how that assembly is installed and maintained. It is far stricter than ordinary joinery practice: clearances between the leaf and the frame and at the bottom of the door are limited, the door has to latch and self-close, and field modifications that are routine on an unrated door — planing the leaf, drilling for a different lock case, adding a vision panel — will void the label unless the manufacturer's listing permits them. Steel frames and leaves for this work are specified under ANSI/SDI A250.8; wood flush doors under the WDMA industry standard for architectural wood flush doors.
Sound is the quieter failure. A partition's laboratory rating is measured under ASTM E90 and expressed as a single number by ASTM E413, and none of that describes a wall with a door in it: door assemblies are tested separately under ASTM E1408, and the finished partition performs closer to its weakest element than to its average. Perimeter seals, a drop seal or a sealed threshold, and a continuous bead of acoustic sealant behind the frame all do more than upgrading the leaf alone. It is worth saying out loud when a client asks for a quiet room and an undercut for return air in the same conversation, because the two requirements are pulling in opposite directions and only one of them can win.
Close out on the things that only show once everything else is finished. Operate the leaf through full travel with the floor finish down and the hardware on, check latch engagement at the top and bottom of the strike, and confirm the closer speed and force against the accessibility requirement rather than against how it feels to a person standing up — the ADA sets an opening force limit for interior hinged doors and a minimum closing time, and a fire door's force is a matter for the authority having jurisdiction because it has to latch. Then take a tape back to both landings, with the furniture in and the flooring laid, and confirm the clear space you designed is still there. That last measurement is the one nobody takes and the one an inspector starts with.
What to fix before the jacks are cut
Six decisions, all of them cheaper on paper than on the wall, and the last two are the ones that get left until the floor is down.
- Clear opening width required, and under which document — The ADA figure, an Approved Document M figure and an AS 1428.1 figure are not interchangeable — confirm what has been adopted locally.
- Leaf and frame sizes actually available — Measure reused leaves rather than trusting the schedule; an out-of-production frame section changes every width below it.
- Rough opening, width and height — Frame size plus shim space each jamb, head clearance, pan thickness, anything packed under the pan, and an out-of-square allowance.
- What the wall carries, and how it will be held — Needle and prop scheme, sole plates sized for what they stand on, and the lintel's end bearing at both reveals.
- Maneuvering clearance on both faces — Run the approach direction and push or pull side separately for each side of the door; the two answers are rarely the same.
- Finished floor level each side, and the undercut — Fix it before the door schedule is released, and check the manufacturer's limit before trimming any leaf.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.