How much will new flooring raise the floor, and when to trim doors
By Michał Białas · Last updated
Add up every new layer — leveler, thinset or adhesive, membrane, underlayment and the tile or planks — then subtract the old covering you take up. Tile over a thin leveler typically raises the floor 3/4 to 1 in (15–25 mm), laminate about 3/8 in (10 mm). Check each door before you start: if the gap left under it is smaller than you want, trim it by the difference.
Add up every layer
The height of a new floor is simply the sum of its layers. The ones people forget are the thin ones: a thinset bed under tile, a self-leveler pour, an uncoupling membrane or a foam underlayment each add a few millimeters, and together they can decide whether a door still swings. Thinset is easiest to estimate from its coverage — 1 lb of powder per sq ft makes a bed a little over 1/8 in thick (1 kg/m² ≈ 0.7 mm) — so a larger notch or back-buttering raises the floor too.
| Layer | Typical thickness |
|---|---|
| Self-leveler | 1/8–1/2 in (3–12 mm) per pour |
| Sand-cement screed or mortar bed | 1 1/4–2 in (30–50 mm) or more |
| Thinset bed | 1/8–3/16 in (3–4 mm) |
| Uncoupling membrane | 1/8 in thin, 5/16 in thick (3–7 mm) |
| Underlayment | 1/16–1/4 in (1.5–6 mm) |
| Porcelain tile | 3/8 in (10 mm) |
| Click vinyl, laminate, engineered wood | 3/16 in, 5/16–1/2 in, 9/16 in (5, 8–12, 14 mm) |
Subtract what you take up
Only the old covering you remove gives height back. Sheet vinyl is about 1/8 in (3 mm), laminate with its pad about 3/8 in (10 mm), tile with thinset or carpet with its pad about 1/2 in (12 mm). If you keep an old floor and lay over it, nothing comes back — which is why an overlay often needs more door trimming than a full tear-out.
Over an out-of-level subfloor the leveling layer is deeper at the low spots, so the raise is a range rather than a single number. Measure the depth at each doorway; the floor height calculator shows the range from the high spot to the low spot when you use the level-difference or height-grid mode.
Door clearance and when to trim
- Measure the gap from the bottom of each door to the floor that is there now.
- Subtract the net raise: that is the gap left after the new floor goes down.
- Compare it with the gap you want to keep — about 3/8 in (10 mm), more where the door is the return-air path for heating or cooling.
- Trim the difference, rounded up to the next 1/16 in or 1 mm.
- Undercut the jambs and casing at the new floor height so the flooring slides underneath.
Example 1 (feet): tile over self-leveler, sheet vinyl taken up
- Take up sheet vinyl, 1/8 in (3.2 mm). Put down 1/4 in (6.35 mm) of self-leveler, thinset at 1.23 lb per sq ft (a 4.2 mm bed) and 3/8 in (9.525 mm) porcelain.
- Added: 6.35 + 4.2 + 9.525 = 20.1 mm, about 13/16 in. Net raise: 20.1 − 3.175 = 16.9 mm, about 11/16 in.
- The door clears the old floor by 3/4 in (19.05 mm): 19.05 − 16.9 = 2.15 mm is left.
- To keep 3/8 in: 9.525 − 2.15 = 7.37 mm → trim 5/16 in. The 11/16 in step to the next room needs a threshold or ramp profile.
Example 2 (meters): tile replaces laminate
- Take up laminate with underlay, 10 mm. Put down 3 mm of self-leveling compound, adhesive at 4 kg/m² (2.8 mm) and 10 mm tile.
- Added: 3 + 2.8 + 10 = 15.8 mm. Net raise: 15.8 − 10 = 5.8 mm.
- The 12 mm door gap shrinks to 6.2 mm; to keep 10 mm, trim 3.8 mm, rounded up to 4 mm.
- The 5.8 mm step to the next room is under 6 mm, so a flat threshold strip works.
Transitions at doorways
| Step between rooms | Transition |
|---|---|
| Up to 1/4 in (6 mm) | Flush transition or T-molding |
| 1/4–1/2 in (6–13 mm) | Reducer, beveled no steeper than 1:2 |
| Over 1/2 in (13 mm) | Threshold or ramp profile, or a thinner build-up |
These limits follow a common accessibility rule of thumb (US ADA 2010 §303) and are worth following at home too: steps over 1/4 in catch toes and vacuum cleaners. If the next room is being redone as well, enter how much its floor rises — the step is the difference between the two. The transition strips themselves are on the shopping list in the floor renovation calculator.
Other places the height matters
- Dishwashers and other built-in appliances: check that they still slide out under the counter.
- The bottom stair: a higher landing floor makes the first riser shorter than the rest.
- Toilet flanges and floor drains: they may need an extension ring.
- Baseboards, door stops and cabinet toe kicks: plan their height after the new floor.
Common mistakes
| Mistake | Result |
|---|---|
| Forgetting the thinset or adhesive bed | Floor ends up 1/8–3/16 in higher than planned |
| Trimming doors before checking the leveling depth at the doorway | A second trim after the pour |
| Laying over the old floor without counting it | Doors and appliances that no longer clear |
| Ignoring the step to the next room | A trip edge where a reducer was needed |
If the build-up is close to a limit, a thinner leveler or a membrane instead of a mortar bed often solves it — see screed vs self-leveling compound.
Frequently asked questions
How much does tile raise the floor?
Porcelain set in thinset adds about 1/2 in (13 mm): 3/8 in of tile and a 1/8–3/16 in bed. Add any leveler or membrane underneath and subtract the covering you take up.
Do I have to trim my doors for new flooring?
Only if the gap left under the door is smaller than you want. Measure the gap now, subtract the net raise and compare it with the 3/8 in (10 mm) you want to keep.
Should I undercut the door jambs?
Yes. Cut the jambs and casing at the new floor height, using an offcut of the flooring on its underlayment as a guide, so the floor slides underneath with its expansion gap.
What if the new floor is much higher than the next room?
Use a reducer up to 1/2 in (13 mm) and a threshold or ramp profile above that, or make the build-up thinner with a thinner leveler, underlayment or tile.