How much will new flooring raise the floor?
Every layer you put down adds height, and only the old covering you take up gives some of it back. A tile floor over a thin self-leveler typically adds 3/4 to 1 in, laminate on foam underlayment about 3/8 in, and a 2 in mortar bed with tile 2 1/2 in or more. It shows up at every door, at the next room and under the dishwasher.
The calculator takes the layers you set up — leveler or screed, thinset bed, uncoupling membrane, underlayment, tile or planks — and stacks their thicknesses from the bottom up. Thinset is worked out from how much powder goes on each square foot, so a bigger trowel notch or back-buttering shows up in the height too. When the subfloor is out of level, the leveling layer is deeper at the low spots, so you also get a range from the high spot to the low spot.
Typical thickness of each layer
Typical values; your data sheet wins, and every layer can be changed:
- Self-leveler: 1/8 to 1/2 in per pour; a sand-cement or mortar bed 1 1/4 to 2 in or more.
- Thinset bed: about 1/8 in with a 1/4 in notch, 3/16 in with a 1/2 in notch and back-buttering.
- Uncoupling membrane: 1/8 in thin, 5/16 in thick or heated-floor.
- Underlayment: 1/16 in for vinyl plank, 1/8 in foam, 1/4 in cork.
- Tile: 1/4 to 3/8 in porcelain, up to 3/4 in natural stone.
- Planks: about 1/8 in glue-down LVT, 3/16 to 1/4 in click vinyl, 5/16 to 1/2 in laminate, 9/16 in engineered wood.
- Old covering taken up: sheet vinyl about 1/8 in, laminate with underlayment 3/8 in, tile with thinset or carpet with pad 1/2 in.
The floor height formula
H_add = Σ layer thicknesses; ΔH = H_add − H_removed; trim = max(0, Q − (G − ΔH))
G is the gap under the door today, Q the gap you want to keep (3/8 in by default) and H_removed the old covering you take up. Thinset beds are estimated from their coverage: 1 lb of powder per sq ft makes a bed a little over 1/8 in thick. The step at the doorway is ΔH minus any change on the other side.
Worked example
- Take up sheet vinyl, 1/8 in. Put down 1/4 in of self-leveler, thinset with a 1/2 in notch and back-buttering (1.23 lb per sq ft, a 3/16 in bed) and 3/8 in porcelain.
- Added: 1/4 + 3/16 + 3/8 in ≈ 13/16 in (20.1 mm). Net raise: 13/16 − 1/8 = 11/16 in (16.9 mm).
- The door clears the old floor by 3/4 in, so about 1/16 in is left. To keep 3/8 in, trim 5/16 in off the door.
- The step to the old floor next door is 11/16 in — more than 1/2 in, so use a threshold or ramp profile.
How much to cut off a door
Measure the gap between the bottom of each door and the floor that is there now, and enter it under the door. The calculator subtracts the net raise and shows the gap that is left. If that is less than the gap you want to keep — 3/8 in by default — it tells you how much to trim, rounded up to the next 1/16 in. Keep more if the gap under the door is the return-air path for your heating or cooling.
Trim before the new floor goes down if you can, and undercut the door jambs and casing at the same height so the flooring slides underneath instead of being scribed around them. A door that does not swing over the new floor, such as an exterior door opening out, can be switched off.
Transitions between rooms of different height
Where the new floor meets a room that keeps its old floor, the step is the net raise. A rule of thumb from accessibility guidance (US ADA 2010 §303): up to 1/4 in can be flush or covered with a T-molding, 1/4 to 1/2 in needs a reducer beveled no steeper than 1:2, and anything higher needs a threshold or ramp profile — or a thinner build-up. If the next room is being redone too, enter how much its floor goes up and the step shrinks to match. The transition strips themselves are on the list in the floor renovation calculator.
Frequently asked questions
How much does tile raise the floor?
Porcelain set in thinset adds about 1/2 in: 3/8 in of tile and a 1/8 to 3/16 in thinset bed. Add any leveler or membrane underneath and subtract what you take up.
Do I have to cut my doors for new flooring?
Only if the gap left under the door is smaller than you want. Enter the gap you have now; if the floor goes up by more than that gap minus about 3/8 in, the door needs a trim.
How much gap should be under an interior door?
About 3/8 in is common. A door that lets air return to the furnace or air handler often needs more, so check before you trim.
Should I undercut the door jambs?
Yes. Cut the jambs and casing at the height of the new floor — use a scrap of the new flooring with its underlayment as a guide — so the floor slides underneath with its expansion gap.
What if the new floor is higher than the next room?
Use a transition that matches the step: a T-molding up to 1/4 in, a reducer up to 1/2 in and a threshold or ramp above that. If the step is too big, a thinner leveler, underlayment or tile brings it down.
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