What problem this solves
A typical renovation involves two flooring materials meeting at a doorway: tile in the bathroom, wood in the hallway; LVP in the kitchen, carpet in the bedroom. The two materials often have different thicknesses (tile 10 mm + thinset 5 mm + backer board 6 mm = 21 mm total; engineered wood 12 mm + underlay 3 mm = 15 mm total). A 6 mm height difference at the threshold is a trip hazard and an eyesore. The calculator finds the right transition profile and tells you when an undercut of the higher material is needed for a flush finish.
Designers usually plan transitions after both floors are installed — which means the threshold becomes a problem to solve rather than a detail to design. Planning it before the install is dramatically cheaper: the higher material can be ordered with an underlayment adjustment, or the subfloor can be built up under the lower material.
Who it’s for
- Designers specifying transition strips in floor-plan drawings
- Tile installers checking finished heights before laying
- Renovation contractors quoting a multi-material floor
- Homeowners DIY-ing adjacent floor materials
Why height differences matter
A 10 mm height difference at a doorway is a trip hazard for guests, a wheelchair obstacle, and a place where the vacuum catches. Building code often limits threshold heights to 13 mm in residential and 6 mm in ADA-accessible spaces. The calculator applies both thresholds and flags when an undercut or transition strip is required.
Limitations
- Subfloor assumed flat; uneven subfloors need self-levelling compound (not modelled).
- Carpet thickness varies with padding; calculator assumes standard residential padding.
- Curved transitions (e.g. for shower entries) follow plumbing-specific rules.
- No modelling of expansion gaps required at the threshold for wood or LVP.
- Strip length assumes the doorway width; mitre cuts and waste add 5–10% to linear feet needed.
Practical rules of thumb
For tile meeting wood: a Schluter Dilex or T-moulding covers the height difference and lets the wood expand. For wood meeting carpet: a tack strip + carpet edge strip (the carpet is stretched over the strip and tucked). For LVP meeting carpet: a vinyl cap or transition strip. Always leave a 6–10 mm expansion gap at the threshold for wood/LVP — the strip covers it.