Overview
Interior finishing runs from the ground up, quite literally — subfloor first, then finished flooring, then wall treatments, each depending on the layer beneath it being correctly sized and installed. This guide walks through that sequence for a typical room finishing project, covering flooring, carpet (including stairs), epoxy coatings, and the most common wall treatments: shiplap, wainscoting, and wallpaper.
Follow the order below for a full room, or jump to the specific material you're working with.
Step 1: Size the Subfloor
Before any finished flooring goes down, subfloor plywood needs to match the span between floor joists — undersized subfloor thickness leads to flex that can crack tile or cause squeaking under carpet or hardwood over time.
The Plywood Calculator sizes sheet count and recommends thickness based on your room dimensions and joist spacing.
Step 2: Order Finished Flooring or Carpet
Finished flooring calculations depend on material type. Hard flooring (plank, tile) is calculated from square footage plus a waste allowance — 10% standard, 15% for diagonal layouts. Carpet is sold in fixed roll widths, so room layout relative to that width affects total material and seam placement.
The Flooring Calculator handles hard flooring square footage, and the Carpet Calculator accounts for standard roll widths and seaming for carpeted rooms.
Step 3: Calculate Stair Carpet Separately
Stairs need their own carpet calculation, not a flat square-footage estimate, because each step's tread, riser, and nosing wrap consumes significantly more material per horizontal foot than flat flooring — often 2–2.5 times more.
The Stair Carpet Calculator sums material needs step by step, accounting for this geometry.
Step 4: Apply Epoxy Coating Where Needed
For garage floors, basements, or workshop spaces, epoxy coating coverage depends heavily on substrate porosity — a rough or previously uncoated concrete surface absorbs significantly more product than a smooth, sealed one.
The Epoxy Calculator adjusts coverage estimates for substrate condition and number of coats, which a flat per-square-foot rate would miss.
Step 5: Finish Walls with Shiplap or Wainscoting
Wall treatments differ in coverage area: shiplap typically covers a full wall floor-to-ceiling, while wainscoting covers only a fixed lower portion (commonly 32–36 inches), regardless of overall ceiling height — meaning wainscoting material needs don't scale with room height the way shiplap does.
The Shiplap Calculator and Wainscoting Calculator reflect these different coverage patterns, both subtracting door and window openings from the calculated area.
Step 6: Calculate Wallpaper with Pattern Repeat
Wallpaper material needs depend not just on wall area but on pattern repeat — large repeating patterns require extra material at each strip to align with the previous one, which can increase total rolls needed by 15–20% over a small or random-match pattern.
The Wallpaper Calculator factors in your specific pattern repeat length alongside wall area to calculate accurate roll count.
Key Terms
- Subfloor — the structural layer beneath finished flooring, typically plywood, that must match joist spacing to avoid flex
- Waste allowance — the extra percentage of material ordered beyond the exact calculated area to cover cuts and installation loss
- Roll width — the fixed width carpet and some wallpaper is manufactured in, which determines seam placement across a room
- Nosing — the rounded or overhanging edge of a stair tread, which requires extra carpet or flooring material to wrap around
- Substrate — the underlying surface (such as concrete) that a coating like epoxy is applied to, whose porosity affects coverage
- Pattern repeat — the vertical distance before a wallpaper's pattern repeats, which determines how much material is lost aligning adjacent strips
- Wainscoting — a paneled wall treatment applied to the lower portion of a wall, typically topped with a chair rail or cap trim