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HENRY 549 FeatherFinish Calculator: How Many 7 lb Bags?
Enter the floor area and the average thickness you will trowel on to see how many 7 lb (3.2 kg) units of HENRY 549 FeatherFinish to buy. W.W. Henry rates one unit at up to 24 sq ft at 1/8 inch; the calculator scales that figure to your thickness and never uses more coverage than the data sheet prints. Figures come from the HENRY 549 technical data sheet linked from the official wwhenry.com product page.
HENRY 549 FeatherFinish coverage
| Thickness | US | Metric |
|---|---|---|
| 1/16 in (1.6 mm) | 48 sq ft | 4.5 m² |
| 1/8 in (3.2 mm) | 24 sq ft | 2.2 m² |
| 1/4 in (6.4 mm) | 12 sq ft | 1.1 m² |
| 1/2 in (12.7 mm) | 6 sq ft | 0.6 m² |
Source: The W.W. Henry Company Technical Data: HENRY 549 FeatherFinish Underlayment Patch and Skimcoat, Rev. 08/05 (PDF linked from the current product page), read 2026-11-02.
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. Manufacturers rate the bag at one or two fixed thicknesses, and where the data sheet gives a range this calculator divides by the low end, 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 24 sq ft at 1/8 in, so at 1/8 in it covers 24 × 0.125 ÷ 0.125 = 24 sq ft. 132 ÷ 24 = 5.5 bags, so buy 6 (42 lb).
HENRY 549 FeatherFinish key specs
| Product type | Floor patch and skim coat |
|---|---|
| Bag size | 7 lb (3.2 kg) |
| Mixing water per bag (max) | 1.75 US qt (1.66 L) |
| Thickness range | 1/16–1/2 in |
| Coverage per 7 lb unit | up to 24 sq ft at 1/8" (3 mm); skim coat over concrete 70–110 sq ft; over plywood up to 198 sq ft (all from the data sheet) |
| Thickness | true featheredge up to 1/2" thick over large areas in one application; any thickness in small, well-defined areas such as thresholds, birdbaths and height transitions |
| Mixing water | 1.75 US qt (1.66 L) per 7 lb unit; by volume 2 parts powder to 1 part water; extra water weakens it and slows hardening |
| Open time to flooring | as soon as it can be worked on without damage, in as little as 15–20 minutes, for ceramic tile, VCT, sheet vinyl and carpet; 16 hours for parquet, athletic flooring and moisture-sensitive adhesives such as epoxies or urethanes |
| Priming | no primers or additives needed, according to the data sheet |
| Substrates | interior concrete, masonry, wood, cementitious terrazzo and ceramic tile; properly prepared non-water-soluble adhesive residue such as cutback, on concrete only |
| Limits | subfloor structurally sound, clean and dry, surface at least 50°F; for embossed felt-backed sheet vinyl, W.W. Henry points to HENRY 550 EmbossPro instead |
| Base | Portland cement-based patch and skimcoat |
| Data sheet date | sheet marked Rev. 08/05; the PDF is the one the current product page links to (uploaded 2019-06) |
What HENRY 549 FeatherFinish is for
HENRY 549 FeatherFinish is a Portland cement-based patch and skimcoat from The W.W. Henry Company, the flooring-installation brand that is now part of ARDEX. It is mixed with water only and trowelled on to give a smooth, permanent surface before the finished floor goes down: smoothing ridges, filling cracks, gouges and joints, featheredging a transition, or skimming over a rough slab. The data sheet's headline is speed. It dries in as little as 15 minutes, so tile, VCT, sheet vinyl or carpet can follow almost straight away.
W.W. Henry lists interior concrete, masonry, wood, cementitious terrazzo and ceramic tile as substrates, plus thin, well-bonded residues of cutback and other adhesives that are not water-soluble, on concrete only. The data sheet says no primers or additives are needed. It is a patch, not a floor: it goes under a floor covering. For embossed felt-backed sheet vinyl, Henry points you to its separate HENRY 550 EmbossPro leveler instead.
How the bag count is worked out
HENRY 549 is sold as a 7 lb (3.2 kg) unit of powder, and a fixed weight of powder fills a fixed volume of patch. The data sheet gives one reference point for that volume: up to 24 sq ft at 1/8 inch. Spread the same powder twice as thick and it covers half the area, so the calculator scales linearly from that figure: about 48 sq ft at 1/16 inch, 12 sq ft at 1/4 inch and 6 sq ft at 1/2 inch.
The word "up to" matters. 24 sq ft is what a bag gives in good conditions, not a guaranteed minimum, and Henry does not print a lower bound. The calculator uses 24 because it is the only thickness-based number on the sheet and never goes above it. On an open, rough or thirsty slab, raise the waste figure to 15 or 20 percent rather than trusting the best case.
The skim figures on the sheet, 70 to 110 sq ft over concrete and up to 198 sq ft over plywood, work out to an average layer of roughly 0.7 to 1.1 mm over concrete, a scraped-down skim rather than a fill. They are a useful check on a skim job. If the calculator tells you that a light skim over 200 sq ft needs two or three units, that sits inside Henry's own range.
Choosing the thickness to enter
- Seams, nail heads and trowel marks: 1/16 inch or less. This is where a 7 lb unit goes furthest.
- Patching hollows and low spots: measure the depth of the patched area and run the calculator for that area alone.
- Thresholds and height transitions: these taper from full depth to a featheredge, so use roughly half the deepest point as the average thickness.
Most real jobs are a mix of these. The honest way to price one is to split it into zones, run the calculator once for each and add the units. Powder is cheap. Running out with the last bucket already going off is not.
Thickness limits
From a true featheredge up to 1/2 inch over large areas, in one application. In small, well-defined areas such as thresholds, birdbaths and height transitions, the data sheet allows any thickness. Once a whole room needs more than 1/2 inch, a self-leveling underlayment is cheaper and flatter. W.W. Henry's own is HENRY 555 LevelPro, and the self-leveler calculator compares it with the other brands.
Mixing, water and timing
A full 7 lb unit takes 1.75 US quarts (about 1.66 L) of water. For part of a bag, use 2 parts powder to 1 part water by volume. Put the water in the container first, add the powder while mixing by hand or with a drill, and mix until there are no lumps. A drill gives a creamier, smoother mix. Do not add extra water: Henry warns it weakens the patch and makes it take longer to harden. The water figure in the calculator result is simply 1.75 quarts times the number of units.
Apply it with a steel trowel, pressing hard enough to fill every defect and to featheredge into the surrounding floor. The data sheet says no minimum thickness has to be left on the substrate, so use the least material that gives the smoothness you need. Ceramic tile, VCT, sheet vinyl and carpet can follow as soon as the patch can be walked and worked on without damage, in as little as 15 to 20 minutes. Parquet, athletic flooring and flooring set with moisture-sensitive adhesives such as epoxies or urethanes need 16 hours.
Preparation
The subfloor must be structurally sound, solid and completely clean: remove wax, sealers, curing compounds, old patching compounds, dust, oil and anything else that could stop the bond. Where preparation is needed, it must be mechanical. The data sheet rules out sweeping compounds, solvents and acid etching. The surface must be dry and at least 50°F. Over adhesive residue, the residue must not be water-soluble, must not react with the new flooring adhesive, and must be wet-scraped down to a thin, well-bonded film first.
Compared with the other patch products
The floor patch calculator runs every patch on this site against the same area and thickness. Per pound of powder, HENRY 549 and ARDEX Feather Finish come out almost the same, but the ARDEX bag is 10 lb against Henry's 7 lb, so you buy fewer ARDEX bags for the same job. MAPEI Planipatch comes in a bigger 25 lb bag, but its data sheet rates that bag at 25 to 35 sq ft at 1/8 inch, so per pound it covers well under half as much as either featheredge patch.
FAQ
How much does a bag of HENRY 549 FeatherFinish cover?
The W.W. Henry data sheet says a 7 lb unit covers up to 24 sq ft at 1/8 inch. Because the bag is a fixed volume of powder, that is about 48 sq ft at 1/16 inch and 12 sq ft at 1/4 inch. As a thin skim the sheet gives 70 to 110 sq ft over concrete and up to 198 sq ft over plywood. Note the words 'up to': 24 sq ft is the best case, so on a rough or very porous floor plan on fewer square feet per bag and raise the waste figure.
How many bags of 549 do I need for 100 sq ft?
At 1/8 inch with 10% waste, 100 sq ft is 110 sq ft to cover, and 110 ÷ 24 = 4.6, so 5 units (35 lb of powder). At 1/16 inch the same floor needs 3 units; at 1/4 inch it needs 10. If you are only filling seams and hollows, measure the patched area rather than the whole room.
How much water do I mix with HENRY 549?
1.75 US quarts (about 1.66 L) of water for the whole 7 lb unit, or 2 parts powder to 1 part water by volume for smaller batches. Put the water in the bucket first, add the powder and mix by hand or with a drill until lump-free; a drill gives a creamier mix. The data sheet warns that extra water weakens the patch and makes it take longer to harden.
How thick can HENRY 549 be applied?
From a true featheredge up to 1/2 inch over large areas in one application. In small, well-defined areas such as thresholds, birdbaths and height transitions it can go to any thickness. For a whole floor deeper than 1/2 inch, a self-leveling underlayment such as HENRY 555 LevelPro is the better tool.
How soon can I put flooring over 549?
As soon as you can work on it without damaging the surface, in as little as 15 to 20 minutes, for ceramic tile, VCT, sheet vinyl and carpet. Parquet, athletic flooring and floors set with moisture-sensitive adhesives such as epoxies or urethanes need 16 hours.
Is HENRY 549 the same as ARDEX Feather Finish?
No. Both are cement-based featheredge patches and W.W. Henry is part of ARDEX, but they are different products with different bags: HENRY 549 is a 7 lb unit rated at up to 24 sq ft at 1/8 inch, ARDEX Feather Finish is a 10 lb bag rated at 33.3 sq ft at 1/8 inch. Per pound the two come out about the same; per bag, the ARDEX bag goes further because it holds more powder.
W.W. Henry Company and HENRY 549 FeatherFinish are trademarks of their owner. This page is an independent estimate based on the published data sheet; check the bag label before mixing.