Planing a door is one of those jobs that looks simple and punishes carelessness. Take too much off and you cannot put it back. Take it off the wrong edge and a panelled door stops looking symmetrical. Take it off a fire door and you may have quietly destroyed its certification. This guide covers how much you are allowed to remove, which tool to use, how to keep the edge square, and how to seal the door afterwards so it does not swell straight back up.
Short answer: do you actually need to plane it?
Only plane the door if it genuinely does not fit the opening, or if it has swollen permanently. A door that binds in one spot is usually a hinge problem, a lining problem or a seasonal moisture problem, and all three are fixable without touching a plane. Planing is the last resort, not the first move, because it is the only step in the whole job that cannot be undone.
What planing a door actually means
Planing is not sanding
A plane cuts a shaving with a blade. A sander abrades the surface with grit. They do different jobs and they are not interchangeable. A sander will take an hour to remove what a sharp plane removes in a minute, and it will leave a rounded, out of square edge while it does it. Sanding is what you do after planing to tidy the surface, not instead of it.
Where the material comes off
Width is taken off the two vertical stiles. Height is taken off the top or bottom rail. On a lipped door you are cutting into the solid timber lipping, which is exactly what it is there for. Once you plane past the lipping you are into the core, and on many doors that is the point of no return.
The trimming allowance is the hard limit
Every manufactured door has a stated trimming allowance. It is not a suggestion. It is the amount of material the manufacturer has designed into the door so that the construction still works afterwards. Find that figure on the product page before you mark anything out.
When trimming is the wrong answer
If the door is more than about 15mm too big in either direction, you have almost certainly bought the wrong size. Order the correct size rather than trying to plane your way out of it. We hold over 700 products in internal doors in a wide spread of sizes, and our door size guide covers what is standard.
Before you touch a plane
Check the lining, not the door
Doors get blamed for problems that belong to the opening. Check both legs of the lining for plumb, check the head is level, and check the lining is not twisted. If the lining is out, planing the door will produce a door that only fits a wonky opening, and it will look wrong forever. Our comparison of door frames against door linings covers what you are working with.
Let the door acclimatise
A new door arrives from a warehouse with a different humidity to your house. Stand it upright in the room it will live in, off the floor, for at least 48 hours before you cut it. A door trimmed cold and then hung in a heated house will shrink after you have finished and leave you with gaps.
Work out whether it is seasonal swelling
A door that sticks in August and swings freely in February has not grown. It has absorbed moisture from the air and it will give it back. If you plane it in summer, you will have a rattling, draughty door by Christmas. Our guide on stopping doors swelling covers how to tell the difference.
Check the hinges first
A binding door very often has a hinge recess cut too deep, which pushes the door across the opening and makes it catch on the closing edge. Shimming that recess with a slip of card takes two minutes and costs nothing. Our guide on where to fit door hinges covers the diagnosis, and we hold over 350 products in door hinges.
Working out how much to remove
Measure the opening in three places
Measure the width at the top, middle and bottom of the opening, and the height at both sides and the centre. Openings are rarely square. Work to the smallest reading, because that is the dimension the door actually has to pass through. Our guide on how to measure a door covers the method.
The gaps you are aiming for
Around 3mm at the head and down both stiles on a standard internal door, and 6mm to 10mm at the bottom depending on the floor finish and whether the room relies on that gap for ventilation. Subtract those gaps from the opening to get your target door size.
Share the cut across both edges
If you need to lose 8mm of width, take 4mm off each stile. Taking it all off one side leaves a panelled door with visibly unequal margins either side of the panel, and it shifts the position of the internal lock block that your latch has to bite into.
Height: top rail or bottom rail
Take height off the bottom in almost every case. The bottom rail is usually the deeper of the two, the cut edge is hidden by the floor and the threshold, and any small imperfection in the cut disappears from view. Only take material off the top if the door has a specific feature at the bottom that you must preserve.
Marking the line
Mark with a sharp pencil against a straightedge, then score along it with a marking knife. The knifed line gives your blade something to register against and, on a veneered door, it is what stops the face fibres tearing out as the blade exits.
The trimming allowance in detail
What the figure means
A stated allowance is the total material you may remove, spread over the door, not the amount you may take from each edge. A door quoted at 32mm is not offering you 32mm off each side. Treat it as roughly half that figure across the width and half across the height, and check the specific product page.
Typical allowances
Lightweight hollow core doors often allow very little, because there is only a narrow solid rail behind the edge. Engineered solid core doors with real timber lippings are far more generous. The Deanta Windsor white primed door, for example, is listed with a 32mm allowance and a real oak lipping, which is unusually forgiving.
Fire doors have almost none
Fire doors are certified as a tested assembly and their allowance is deliberately small. Exceeding it invalidates the certification of the entire door. If a fire door will not fit, the answer is a different size, never a bolder plane. We hold over 150 products in FD30 fire doors and over 240 in fire doors overall.
What happens if you go past it
On a hollow core door you break into the void and the edge collapses. On an engineered door you lose the lipping, so the edge will not hold screws, will not take a clean paint finish and will chip every time the door swings past the frame. In both cases the guarantee goes with it.
Choosing the right tool
The previous version of this guide advised using a rebate or shoulder plane on softwood and a block or jack plane on hardwood. That advice was wrong, and it is worth correcting properly because it would send you to the wrong tool entirely.
The jack plane
A jack plane, usually a number 5, is the right tool for taking material off the long edge of a door. Its sole is long enough to bridge high spots and produce a genuinely straight edge, which a short plane cannot do. If you only own one plane for this job, own this one.
The block plane
A block plane is small, held in one hand, and has its blade set at a low angle. It is for end grain, chamfers, easing arrises and tidying up. It is useful at the end of the job and on the top and bottom rails. It is not the tool for straightening a two metre edge.
What a rebate or shoulder plane is actually for
A rebate plane cuts a rebate, which is a step along an edge. A shoulder plane trims the shoulders of a joint. Neither is chosen on the basis of whether the timber is hard or soft, and neither is a door trimming tool. They belong to joinery work, not to fitting a door.
The electric planer
A power planer removes material fast and is the usual choice when you have a houseful of doors. Speed is also its danger, because it will take 2mm off in a single careless pass. Set the depth low, keep both hands on it, and let the machine do the cutting rather than pushing it.
Belt sanders
A belt sander can be used for very small adjustments and for cleaning up after a saw, but it rounds edges over easily and it will not give you a square edge on its own. Use it as a finishing tool, not a shaping one.
A saw for larger cuts
Anything over about 5mm off the height is faster and more accurate with a circular saw run against a clamped straightedge, followed by a plane to clean the edge. Trying to remove 15mm of height with a hand plane is an afternoon of work and an uneven result.
Keeping the blade sharp
A blunt blade does not cut, it crushes. It tears grain, it wanders off square, and it makes you push harder, which is when accidents happen. Hone the blade before you start rather than halfway through when the edge is already ragged.
Planing the long edges
Set the door up properly
Clamp the door on edge in a portable workbench or between two sturdy trestles, at a height where you can look down the edge. A door that moves while you plane it will produce a wavy edge. This is not the step to improvise.
Which direction to plane
Plane with the grain, not against it. Look at the edge and work in the direction where the fibres lie away from the blade. If you start getting tearout rather than clean shavings, you are going the wrong way, so turn round and work back from the other end.
Depth of cut
Set the blade for a fine shaving. You should be producing something you can see light through. Heavy cuts feel productive and are how people overshoot their line, dig in and tear the grain.
Keeping the edge square
Check the edge against the face with an engineer's square every few passes. A plane pushed with uneven pressure will round the edge over without you noticing, and a rounded edge will not close cleanly against a door stop.
The slight back bevel on the closing edge
The leading edge of the door, the one that swings into the frame, is traditionally given a very slight bevel of about two or three degrees so the corner does not catch on the lining as the door closes. It is a small detail that makes the difference between a door that swings and a door that scrapes.
Checking as you go
Offer the door up to the opening regularly. Ten small checks beat one big mistake. Mark the high spots in pencil while the door is in the opening, then take those off specifically rather than planing the whole edge again.
Trimming the height
Take it off the bottom
The bottom rail is usually deeper than the top rail, the cut is hidden, and it is where you want the extra clearance anyway if you are fitting carpet or a thick floor covering.
Score across the face first
Run a marking knife along your line across both faces of the door before you saw. This severs the surface fibres so the saw cannot tear them out as it exits. On a veneered door this step is the difference between a clean edge and a ruined face.
Saw, then plane
Cut a millimetre or two proud of your line with a circular saw against a clamped straightedge, then take the last of it back to the line with a plane. Sawing straight to a finished line leaves you nothing to correct with.
Watch for the core
On a hollow core door there is only a narrow solid rail at the bottom. Cut too much off and you open the honeycomb, at which point you have to glue a new timber infill into the void before the door is usable. Know your door's construction before you cut.
Veneered and engineered doors
Why veneer tears
A veneer is a thin skin of timber glued to a substrate. It has almost no strength across its thickness, so any blade exiting through it will lift and break it out unless the fibres have already been severed.
Score the line
Marking knife, twice, on both faces. It takes thirty seconds and it prevents the one damage type you cannot really repair.
Plane in from the corners
When planing across the grain on a rail, work in from each corner towards the middle rather than running the plane off the end. Running off the end is exactly where breakout happens.
Repairing a small breakout
A small chip on an edge that will be painted can be filled with a two part wood filler, sanded flush and primed. On a lacquered oak or walnut door it is much harder to hide, which is another argument for scoring the line first. We hold over over 280 products in internal oak doors and over 30 in internal walnut doors, and our comparison of oak against walnut covers how each behaves.
Sealing the cut edges
Why this is not optional
Every surface you expose is bare timber or bare core, and bare timber absorbs moisture from the air. That is what makes doors swell, stick, and eventually bow. Sealing the cut edge is normally a condition of the manufacturer's guarantee as well.
What to seal with
On a door you are painting, primer followed by your topcoat. On a prefinished or lacquered door, a clear sealer or lacquer that matches the existing finish. Do not leave a lacquered door with two raw edges because you could not find a matching product.
The top and bottom edges
Nobody sees the top edge, so nobody seals it, and it sits closest to the warm humid air that collects at ceiling level. Seal it. The bottom edge sits nearest to damp floors and cleaning water, so seal that too. All six surfaces, every time.
Timing
Seal before you hang the door, not after. Once the door is up you cannot properly reach the top and bottom edges, and the temptation to skip them becomes overwhelming. Our guide to maintaining painted doors and our product care advice cover finishing.
Rehanging and checking
One screw per hinge first
Hang the door on a single screw in each hinge and test the swing before you commit. Adjustments at this stage take seconds. Adjustments once every screw is driven do not.
Checking the gaps
Run your eye down the closing edge with the door almost shut. A gap that tapers means the door or the lining is not parallel, not that you need to plane more. Diagnose before you cut again.
The latch and strike
If you have taken material off the closing stile, the latch will now sit further back and the strike plate on the lining almost certainly needs moving. Do not solve this by filing the strike into an oval. Move it properly. We hold over 700 products in locks and latches.
Adjust rather than re plane
Shims behind hinge leaves, moving a strike plate, and easing a stop are all reversible. Planing is not. Exhaust the reversible options first.
Fire doors: read this before you cut anything
The allowance is small and it is binding
Fire doors carry a much smaller trimming allowance than standard doors, and it is stated in the door's certification rather than being a general rule. Exceeding it means the door is no longer the product that was tested.
Do not trim the stiles beyond the allowance
The stiles carry the intumescent seals and the fixings. Cutting into them past the allowance compromises both. If the opening is genuinely too narrow, the opening or the door has to change, not the certification.
Seals and the edge
Intumescent and smoke seals sit in grooves in the door edge or the frame. Any trimming has to leave those grooves and seals intact and correctly positioned. Check before you mark out, not after.
If it will not fit, buy the right size
This is not a case where enthusiasm is rewarded. Our comparison of FD30 against FD60 and our guide to fire door materials cover specification, and we hold 8 products in FD60 fire doors alongside the FD30 range.
Troubleshooting
The door still binds
Find where. Close the door slowly onto a strip of paper and see where it grips. If it binds at the top of the hinge side, the top hinge recess is too deep. If it binds down the whole closing edge, the door is genuinely too wide.
The door rattles now
You have taken too much off, or the seasonal moisture has dropped. A rattling door is usually fixed at the stop or with a seal rather than by replacing the door.
Draughts around the door
Gaps larger than about 3mm at the head and stiles will be felt. Draught seals fitted to the lining close them without touching the door. Our guide on draughty doors covers the options.
The edge looks torn
Blunt blade, wrong grain direction, or too heavy a cut. Sharpen, reverse direction and take finer shavings. Sand the damaged section back with a block, not by hand, so you keep the edge flat.
The door is out of square
Check the edge against the face with a square. Rounded or tapered edges come from uneven pressure on the plane. Correct with light passes concentrating on the high side.
You have taken too much off
A few millimetres of excess gap can be closed with a planted door stop or a draught seal. More than that and you are looking at gluing a new lipping on, which is a repair, or replacing the door. We hold over 20 products in clearance doors if you need a replacement without the full price.
Seasonal movement, and why the door may fit again by itself
Timber takes up and gives back moisture with the humidity around it. In a UK house that means doors are at their tightest in late summer and at their loosest in the middle of a heating season. A door that catches slightly in August and is fine in January is behaving exactly as timber does, and planing it will leave you with a permanently loose door. If a door has genuinely swollen because of a leak, damp or a bathroom with no extraction, fix the source first and let the door dry before you decide anything.
Common mistakes
Planing before checking the lining
You end up with a door shaped to fit a defect.
Taking all the width off one edge
Unequal margins on a panelled door, and a displaced lock block.
Planing in summer
The door is at its largest. Wait, or take less than you think you need.
Skipping the knife line
Thirty seconds saved, a torn veneer earned.
Leaving the cut edges bare
The door will absorb moisture and swell straight back into the problem you just solved.
Using a sander instead of a plane
Slow, rounded edges, and dust everywhere.
Trimming a fire door to fit
The one mistake on this list with consequences beyond the cosmetic.
Frequently asked questions
How much can I plane off a door?
Only as much as the stated trimming allowance, spread across the edges rather than taken from one. Check the product page for the specific figure.
Which plane should I use to trim a door?
A jack plane for the long edges, a block plane for tidying and end grain, or an electric planer if you have several doors to do.
Should I take the height off the top or the bottom?
The bottom, in almost every case.
Do I need to take the door off to plane it?
For the closing edge and the bottom, yes. Small easing of the hinge edge can sometimes be done in place, but you will get a better result with the door on trestles.
What gap should there be around an internal door?
Roughly 3mm at the head and stiles, 6mm to 10mm at the bottom depending on the floor finish.
Can I plane a hollow core door?
A little, yes, but the solid rail behind the edge is narrow. Check the allowance and expect it to be small.
Can I plane a fire door?
Only within the very small allowance stated in its certification. Beyond that the door is no longer certified.
Do I have to seal the edges I cut?
Yes. Bare timber absorbs moisture, swells and bows, and unsealed edges usually void the guarantee.
Why does my door only stick in summer?
Humidity. It is seasonal movement, not a fault, and planing it is the wrong fix.
My door is 20mm too wide, can I plane it?
Almost certainly not. Order the correct size instead.
Related guides and ranges
Before you cut
Read how to measure a door, check the door size guide and confirm whether you need a lining or a frame in door frames against door linings. We hold over 30 products in internal frames.
Hanging it afterwards
Our guide on where to fit door hinges covers setting out, and we hold over 350 products in door hinges, over 50 in fire rated hinges and over 2,900 across door hardware.
Finishing the opening
See our guide to door architraves, plus over 15 profiles in door architraves and over 15 in skirting.
Choosing a door in the first place
We hold over 350 products in fully finished internal doors, over 80 in internal white primed doors, over 280 in glazed doors and over 250 across the Deanta range. Our guide to door finishes covers primed against prefinished.
Why buy your doors from Doors2Floors
We have supplied doors and flooring to homes and businesses across the UK. We hold over 700 products across internal doors and over 90 across external doors, in a wide enough range of sizes that most people never need to plane more than a few millimetres. If you are not sure which size your opening needs, talk to our team before you order, because that conversation is a lot cheaper than a ruined door.
Fire door trimming allowances, certification and any work affecting means of escape should be confirmed with the door manufacturer's documentation and with your local building control body or a competent professional. The guidance above is general and does not replace advice specific to your door or your building.