ARDEX Feather Finish Calculator: How Many 10 lb Bags?

ARDEX Feather Finish coverage

Source: ARDEX Americas Technical Data Sheet: ARDEX FEATHER FINISH Self-Drying, Cement-Based Finish Underlayment, content updated 2026-09-14, read 2026-10-29.

How the calculation works

bags = area × (1 + waste ÷ 100) × thickness ÷ (coverage at reference thickness × reference thickness), rounded up

Patch volume scales with thickness: a skim coat an eighth of an inch thick uses half the powder of a quarter-inch fill. ARDEX rates the bag at a fixed thickness with a coverage range for skim coats, so enter the thickness you will actually trowel on.

Worked example

A 120 sq ft floor patched 1/8 in thick with 10% extra: 132 sq ft to cover. One bag covers 16.7 sq ft at 1/4 in, so at 1/8 in it covers 16.7 × 0.25 ÷ 0.125 = 33.4 sq ft. 132 ÷ 33.4 = 3.95 bags, so buy 4 (40 lb).

ARDEX Feather Finish key specs

What ARDEX Feather Finish is for

ARDEX Feather Finish is a cement-based, self-drying finishing underlayment made in the USA by ARDEX Americas. You mix it with water only and trowel it on thin, from a true featheredge up to whatever depth the job needs, to give a smooth, sound surface before the finished floor goes down. ARDEX names sheet vinyl and VCT as the demanding floor coverings it was built for, and the data sheet advertises installing floor coverings in as little as 15 minutes.

The substrate list is broad: structurally sound concrete, absorbent terrazzo on concrete, non-aluminum metal, untreated plywood, solid hardwood, gypsum, ceramic and porcelain tile, VCT, terrazzo and epoxy floors. It is for interior, dry areas only, on, above or below grade. Like every product on this site it is an underlayment, not a floor: do not use it as a wear surface, and do not count on it as a vapor barrier.

This is professional material. The data sheet says ARDEX does not sell it through home improvement centers, and the coverage in a 10 lb bag is small enough that small mistakes in thickness show up as a whole extra bag.

Why the thickness you enter decides the bag count

Feather Finish is sold as a fixed volume of powder in a 10 lb bag, so a bag covers a fixed volume of patch. ARDEX gives the reference points: 33.3 sq ft at 1/8 inch and 16.7 sq ft at 1/4 inch. Those two numbers are the same volume, just spread differently, which is what makes the linear scaling safe here: at 1/16 inch a bag covers about 67 sq ft, at 1/2 inch about 8 sq ft.

That is why the calculator asks for thickness rather than a coverage option. Enter the thickness you will actually pull with the trowel, not the deepest hollow you can find. A quarter-inch fill over the whole floor uses twice the powder of an eighth-inch skim over the same floor.

Most feather-finish jobs are not a uniform layer over the whole room. They are a mix of seams, hollows, trowel ridges and old adhesive ghosts, plus a skim over the traffic areas. Two practical ways to price it:

• Estimate the covered share. If a third of the floor needs 1/8 inch of fill and the rest needs nothing, use a third of the area in the calculator.
• Split the job. Run the calculator once for the full skim at 1/16 inch and again for the patched zones at 1/4 inch, then add the bags. Bags are cheap to add and expensive to run out of mid-job.

ARDEX notes coverage depends on surface profile, density and porosity, so a rough, open concrete floor can soak up noticeably more than a smooth one. The waste allowance in the calculator covers bucket loss and spillage; on a rough floor, lean towards 15%.

Thickness limits, and when to use a self-leveler instead

The normal maximum is 1/2 inch (12 mm). Above that, ARDEX allows unlimited thickness only in small, well-defined areas over standard absorbent (porous) substrates, for example filling a chase, a deep hollow or the gap round a repaired slab section. Once you are covering a whole room at more than 1/2 inch, the right product is a self-leveling underlayment, and ARDEX points to its own K 15 for that job. This site has K 15 and eight other self-levelers in the self-leveler section.

Over existing tile, VCT and other non-porous surfaces there is a second limit that has nothing to do with the powder: ARDEX warns that a thin cementitious skim over a non-porous surface may not give the new flooring a porous bonding surface, and may not block adhesive migration from the old floor. Check the new flooring manufacturer's minimum thickness requirement before relying on a skim coat there.

Priming

Most applications need no primer at all, which is one reason patch jobs go quickly. Where ARDEX does require it, the primer follows the substrate: gypsum and very absorbent concrete take a double prime of ARDEX P 51 or a coat of ARDEX P 4; metal (interior, non-aluminum) and epoxy flooring systems take ARDEX P 82. If moisture control is needed, that is a separate course of ARDEX MC RAPID or ARDEX VB 100, applied before the patch, and it changes the maximum thickness you can build.

Concrete and other substrates must be sound, clean and free of bond breakers: no curing compounds, sealers, wax, oil or loose material. ARDEX's Proper Prep guidance is worth reading before a large job, because almost every patch failure is a preparation failure.

Mixing and timing

One 10 lb bag takes 2 1/2 US quarts (2.4 L) of clean water. Put the water in the bucket first, add the powder while mixing with a 1/2 inch drill at 650 rpm or more, and mix for 2 to 3 minutes until smooth. Small batches can be mixed by hand with a margin trowel at 2 parts powder to 1 part water by volume. Pot life is only 15 to 20 minutes at 70°F (21°C), so mix what you can place, and retemper with the drill rather than adding water if it stiffens.

Spread with the flat side of a steel trowel first, pressing hard enough to fill every defect and get a mechanical bond, then build to the thickness you want. Substrate and air must stay at 50°F (10°C) or above during installation and cure. Most floor coverings can follow once it has hardened, typically 15 to 20 minutes; wood flooring and high-performance epoxy or urethane adhesives need 16 hours.

Using it as an embossing filler

For embossed, felt-backed residential sheet vinyl, ARDEX mixes Feather Finish with ARDEX P 82 rather than water: 1 part P 82 Part A, 1 part Part B and 2 parts powder. That blend fills the pattern in the thinnest possible layer and covers about 50 sq ft per bag, and the new vinyl can go down after roughly 90 minutes. Note that the filled surface then counts as non-porous, so the vinyl adhesive has to be chosen for that.

What this calculator does not do

It does not decide your thickness, and it does not know how rough your floor is. It also does not model the embossing-filler mix, which uses P 82 instead of water and has its own yield. Use the 100 to 300 sq ft skim figure from the data sheet as a sanity check: if the calculator tells you that a light skim over 200 sq ft needs two bags, that is inside ARDEX's range; if it tells you one bag, your thickness is thinner than a skim coat and the floor will not come out flat.

FAQ

How much does a bag of ARDEX Feather Finish cover?

A 10 lb (4.5 kg) bag covers 33.3 sq ft at 1/8 inch (3 mm) and 16.7 sq ft at 1/4 inch (6 mm), according to the ARDEX Americas data sheet. Coverage scales with thickness: about 67 sq ft at 1/16 inch and about 8 sq ft at 1/2 inch. For a skim coat used only to smooth a surface, ARDEX quotes 100 to 300 sq ft per bag, and about 50 sq ft when it is used as an embossing filler over sheet vinyl. Real coverage depends on how rough and how porous the floor is.

How many bags do I need for a 200 sq ft floor?

Divide the area plus waste by the coverage at your thickness. A 200 sq ft floor skimmed at 1/8 inch with 10% waste is 220 sq ft to cover, and 220 ÷ 33.3 = 6.6, so 7 bags. The same floor at 1/4 inch needs 220 ÷ 16.7 = 13.2, so 14 bags. If you are only filling hollows and seams rather than covering the whole floor, measure the patched area, not the room.

What thickness should I enter for a skim coat?

For filling small hollows, seams and trowel marks, 1/16 to 1/8 inch is typical, and 1/8 inch is what this calculator starts at. A full skim coat over a rough or badly profiled floor is often quoted at 1/16 inch or less. Enter the thickness you will actually pull with the trowel, because the bag count is directly proportional to it: doubling the thickness doubles the bags.

How much water goes in a bag of Feather Finish?

2 1/2 US quarts (2.4 L) of clean water per 10 lb bag, mixed with a 1/2 inch (12 mm) drill at 650 rpm or more for 2 to 3 minutes until lump-free. For small batches ARDEX gives a volume ratio of 2 parts powder to 1 part water, which you can mix by hand with a margin trowel. Extra water weakens the compound and lowers its strength, so do not top it up.

When can I install flooring over it?

For most floor coverings, as soon as it has hardened, typically 15 to 20 minutes at 70°F (21°C) — the data sheet advertises installing floor coverings in as little as 15 minutes. For wood flooring and high-performance adhesives such as epoxy or urethane, wait 16 hours. Cold floors and humid air extend every one of those times, and forced drying is not recommended.

How thick can Feather Finish be applied?

Up to 1/2 inch (12 mm) in the normal case, and to a true featheredge at the thin end. ARDEX allows unlimited thickness only in small, well-defined areas over standard absorbent (porous) substrates, for example filling a chase or a deep hollow. For deeper or larger fills, use a self-leveling underlayment such as ARDEX K 15 instead.

ARDEX and ARDEX Feather Finish are trademarks of their owner. This page is an independent estimate based on the published data sheet; check the bag label before mixing.