Specify it when the asset is vertical above-grade masonry that has to shed wind-driven rain and the substrate is high-pH, efflorescing, or hairline-cracked. Loxon XP goes direct to a pH 13 surface with no alkali-resistant primer, builds 13 to 16.8 mils total dry film in two coats, and bridges cracks to 2.5 mm under EN 1062-7 Class A5. Do not specify it below grade, on horizontal traffic surfaces, or on a wall with documented moving structural cracks.
Flat and Satin Are Not the Same Spec
This is the detail that gets missed on submittal review, because most write-ups treat the sheen as a finish preference. It is not. The satin is a lower-solids formulation, so it costs roughly 12 percent more material per square foot at spec thickness, and it carries fewer third-party approvals. Confirm the sheen before the submittal goes in, not after the material is on site. Numbers below are from the 08/2025 revisions of both data sheets.
Spec Sheet
- COVERAGE PER COAT
- Flat 85–110 sq ft/gal · Satin 75–95 · about 80 on porous or rough stucco
- WET MILS PER COAT
- Flat 14.5–18.5 · Satin 17.0–21.5 · 40 wet mils maximum in one pass
- DRY MILS PER COAT
- Flat 6.5–8.4 · Satin 6.5–8.2
- TOTAL DFT, WATERPROOFING SYSTEM
- Flat 13–16.8 mils · Satin 13–16.4 mils, two coats
- VOLUME SOLIDS
- Flat 45 ± 2% · Satin 38 ± 2%
- PERFORMANCE DATA
- 18.03 perms (ASTM D1653) · 312% elongation (ASTM D412) · 295 psi tensile · 375 psi adhesion (ASTM D4541) · EN 1062-7 Class A5 to 2.5 mm at -10°C · ASTM D6904 wind-driven rain
- APPROVALS
- Flat carries MPI #10 and #40 and the SWRI Wall Coating listing; satin carries neither. Both EPD-NSF certified.
- VOC
- Under 50 g/L (0.42 lb/gal); OTC and OTC Phase II, SCAQMD, CARB SCM 2007 and 2020, Canada, LEED v4 and v4.1
- DRY / RECOAT
- Touch 4 hr at 45°F and above, 6 hr at 35–45°F · recoat 24 hr, 24–48 hr when cold
- MIN APPLICATION TEMP
- 35°F air, surface, and material; 5°F above dew point
- PRIMER
- Self-priming direct to masonry pH 6–13; fresh concrete 7 days cure, shotcrete and gunite 3 days
- SIZES
- 1-gallon, 5-gallon, 55-gallon drum on the specifier channel; 36-month shelf life
- PRICE
- $70–85 / gal street; less on a pro account
Dry, Recoat, and the Cold-Weather Schedule
Both series share the same schedule. Dry to touch is 4 hours at 45°F and above and 6 hours in the 35 to 45°F band; recoat is 24 hours, stretching to 24 to 48 hours when cold. The 35°F application floor is 10 to 15 degrees lower than most exterior acrylics and it buys working days at both ends of the season, but the conditions are strict: air, surface, and material all at 35°F or above, at least 5°F above the dew point, no rain or snow expected within 2 to 3 hours, and no drop below 35°F for 48 hours after application. A freeze in the first night ruins a film that looked acceptable at close of work. On new construction the substrate schedule matters as much as the coating schedule — concrete and mortar want 7 days of cure at 75°F, shotcrete and gunite 3 days. Shelf life is 36 months unopened.
When It Goes Wrong — and How to Fix It
Material shortfall against the takeoff
Why it happens: The single biggest estimating error on this product is running coverage at the high end of the published range on a rough substrate. Rough stucco pulls the flat to about 80 sq ft per gallon per coat, and the satin starts lower at 75 to 95 because of the solids difference.
The fix: Take off at 80 sq ft per gallon and two coats, always. A 10,000 sq ft elevation is roughly 200 to 250 gallons of material, not 100. On anything above a single elevation, order 5-gallon pails and confirm lot numbers match across the order — a batch break mid-wall on a tinted masonry coating shows in raking light and will not blend out.
Pinholes above the 10-per-square-foot acceptance limit
Why it happens: A high-build coating over porous block traps air, and the air returns through the film as voids. The data sheet sets the acceptance criterion at 10 or fewer per square foot precisely because some are expected. Every pinhole is a hole in the barrier.
The fix: Four tactics, and on porous block you need all of them. Two coats with overnight drying between them. Spray with back-rolling, airless at 2300 psi through a .021-inch tip. Power rolling to push material into open block instead of skipping across it. Loxon Acrylic Block Surfacer first on extremely porous block — do not ask a topcoat to do a filler's job.
Submittal rejected on the sheen
Why it happens: The satin, LX21-50, carries no MPI #10 or #40 approval and no SWRI Wall Coating listing. Specifications that reference either number are not satisfied by the satin even though it wears the same product name.
The fix: Specify the series number rather than the words Loxon XP — LX11-50 for flat, LX21-50 for satin — and state the base, because Extra White, Deep, Ultradeep, and Light Yellow tint at different loadings. Resolve the sheen before submittal, not after delivery.
Blistering on a damp or below-grade wall
Why it happens: The film is vapor permeable by design at 18.03 perms so the masonry can dry. Breathability and hydrostatic resistance are opposite properties, and the cautions rule out hydrostatic pressure, below-grade service, and horizontal surfaces where water collects.
The fix: For seepage through a foundation, look at Loxon Water Blocking Primer/Finish, a cementitious waterproofer, or the drainage and grading correction outside the wall. Do not attempt to solve a below-grade water problem with a breathable coating on the interior face.
A correctly coated wall that still leaks
Why it happens: Water finds joints before it finds the field of a wall. ASTM D6904 measures penetration through a coated masonry panel; it says nothing about the perimeter conditions of your building envelope.
The fix: Before coating, route-and-seal anything over hairline with an elastomeric sealant, seal the perimeter of every window and door frame, penetration, and control joint, and confirm parapet caps, copings, and flashings are watertight — the data sheet's soffit allowance is conditional on exactly that. Prime incidental metal with Pro Industrial Pro-Cryl and incidental wood with an exterior latex wood primer. Skip the joint work and the coating gets the blame.
Application Settings That Work
- BRUSH
- Brush is nylon-polyester, roller cover is 1/2-inch to 1-1/2-inch nap synthetic with the longer nap on heavy texture. Wet-film gauge readings during application are the only practical verification, because DFT on a masonry substrate cannot be read with a magnetic gauge. The spec is enforced wet.
- AIRLESS
- 2300 psi through a .021-inch tip, sprayed with back-rolling. Spray delivers the mils; the roller drives them into the texture and closes the voids that decide the pinhole count.
- THINNING
- Do Not Reduce. That is the data sheet's reducer line verbatim. Thinning to ease spraying drops the applied film out of the wet-mil range, and out of the wet-mil range the waterproofing claim does not apply.
- PRIMER
- Self-priming direct to masonry at pH 6 to 13, with no alkali-resistant primer in the stack. Concrete and mortar cure 7 days at 75°F, shotcrete and gunite 3 days. Add 1 coat Loxon Acrylic Block Surfacer on porous block or 1 coat Loxon Conditioner on a soft or dusty substrate. Incidental metal takes Pro-Cryl; incidental wood takes an exterior latex wood primer.
Loxon XP vs a True Elastomeric
This is the substitution question that comes up in value engineering, and it goes both directions. Loxon XP is the middle position between a conventional masonry acrylic and a full elastomeric membrane, and on a stable wall the middle position is the correct one.
| Loxon XP | ConFlex XL / SherLastic elastomeric | |
|---|---|---|
| Film build | 13–16.8 mils total DFT in two coats | Typically higher |
| Elongation | 312% (ASTM D412) | Higher |
| Crack bridging | Class A5, 2.5 mm at -10°C | Greater movement capability |
| Vapor permeance | 18.03 perms — the wall dries out | Lower; can trap moisture in the substrate |
| Dirt pickup | Moderate | Generally worse, softer film |
| Alkali tolerance | Direct application to pH 13, no primer coat in the stack | Check the specific system; alkali primers are common |
| Right when | Substrate is stable and cracks are hairline | Cracks are real and moving |
Specify Loxon XP as the default on stable vertical masonry, and go past it to a real elastomeric only against documented movement — cracks that open and close seasonally, joints wider than 1/16-inch, structures with known thermal cycling. A heavy elastomeric on masonry that does not move is a low-perm blanket over a substrate that needs to dry, and the failure that follows is blistering, not cracking. The 18.03-perm figure is what keeps XP out of that trap. In the other direction, do not let a single-coat scope survive value engineering: the waterproofing claim is a two-coat system claim, and one coat is a maintenance recoat with no test data behind it.
What It's Good At
- +Direct application to masonry at pH 6 to 13, removing the alkali-resistant primer from the stack
- +Documented film build — 13 to 16.8 mils total DFT in two coats with ASTM D6904 wind-driven rain performance
- +Schedule compression on new construction: 7 days on concrete, 3 days on shotcrete and gunite
- +Crack bridging to 2.5 mm at -10°C under EN 1062-7 Class A5, at 312 percent elongation
- +Vapor permeance of 18.03 perms, so the substrate dries instead of blistering under the coating
- +A 35°F application floor, 10 to 15 degrees below most exterior acrylics
- +Third-party position on the flat series — MPI #10 and #40, SWRI Wall Coating, EPD-NSF, LEED v4.1 VOC
What It's Not Good At
- −Coverage economy — 75 to 110 sq ft per gallon per coat, two coats, at $70 to $85 a gallon
- −Pinhole control on open CMU without a block surfacer and disciplined spray-and-back-roll
- −Below-grade service, hydrostatic pressure, and horizontal surfaces that hold water
- −Any reduction; the reducer line reads Do Not Reduce and thinning voids the film schedule
- −The satin series on approval-driven specs — no MPI listing, no SWRI listing, lower solids, worse coverage
- −Structural movement beyond 2.5 mm, which is elastomeric territory
Honest Alternatives
The standard-build rung. Conventional acrylic film, no crack bridging, less money per gallon and better coverage. Correct on a sound, previously coated, low-stress elevation where the scope is appearance and dirt shedding rather than water exclusion.
Sherwin-Williams' own selection guidance points here when the wall needs more than Class A5. Thicker membrane, more material, more labor, lower permeance. Specify only against documented movement, not as a general upgrade.
The same platform with a solar-reflective pigment package. Worth pricing on large south and west elevations in cooling-dominated climates where surface temperature drives both energy load and coating stress.
Built for the same alkali-and-efflorescence problem and common on Southwest stucco. Compare the alkali rating, the stated DFT schedule, and the warranty line by line before substituting — the two are close, and the difference is usually in the film thickness the manufacturer will stand behind.
Loxon XP Questions, Answered
What is Loxon XP used for?
Loxon XP Waterproofing Masonry Coating is a high-build acrylic topcoat for vertical, above-grade masonry: tilt-up, precast and poured-in-place concrete, CMU, split-face block, stucco, and shotcrete or gunite. It goes direct to those surfaces at a pH as high as 13, so green concrete and fresh block need no separate alkali-resistant primer. Two coats at the specified film thickness make it a wind-driven rain barrier. It is not a below-grade waterproofer and not a deck or floor coating.
How many coats of Loxon XP do you need?
Two, and the data sheet states it in capitals. The waterproofing claim is a system claim: two coats of topcoat, 6.5 to 8.4 mils dry per coat in the flat, for 13 to 16.8 mils total dry film, with 10 or fewer pinholes per square foot. A single coat is a colored wall, not a waterproofed one, and none of the test data applies to it. The satin runs 6.5 to 8.2 mils dry per coat for 13 to 16.4 mils total.
What is the difference between Loxon and Loxon XP?
Loxon is the family name across nine products; XP is the high-build waterproofing topcoat inside it. XP lays 14.5 to 18.5 wet mils per coat in flat and bridges cracks to 2.5 mm at -10°C under EN 1062-7 Class A5. The standard-build rung, now sold as Loxon Self-Cleaning Acrylic Coating, builds a conventional acrylic film and does not bridge cracks. Under both sits a set of primers, conditioners, and a block surfacer.
Is Loxon XP elastomeric?
It leans elastomeric but it is not sold as one. The film stretches 312 percent by ASTM D412 and carries Class A5 crack bridging, which is more movement than a normal masonry acrylic and less than a true elastomeric membrane. The trade-off is permeance: at 18.03 perms it dries out, where a heavy elastomeric can trap moisture in the wall. When cracks move more than 2.5 mm, step to a real elastomeric such as ConFlex XL or SherLastic.
Can Loxon XP go over fresh concrete?
Yes, after 7 days of cure at 75°F. Shotcrete and gunite can be coated after 3 days. That is the schedule advantage the pH 6 to 13 rating buys you: no separate alkali-resistant primer, no 28-day wait, and one less coat in the stack on a new tilt-up or precast elevation.
What sheens does Loxon XP come in?
Flat, series LX11-50 at 0 to 10 units on an 85-degree meter, and Satin, series LX21-50 at 10 to 20 units on a 60-degree meter. They are not interchangeable specs. The flat is 45 percent volume solids and covers 85 to 110 sq ft per gallon; the satin is 38 percent and covers 75 to 95. Only the flat carries MPI #10 and #40 and the SWRI Wall Coating listing.
Can Loxon XP be used below grade or on a basement wall?
No. The data sheet rules out hydrostatic pressure, below-grade use, and horizontal surfaces where water collects. Loxon XP is vapor permeable by design so the masonry can dry, and a breathable film cannot hold back water under pressure. For seepage through a foundation, look at Loxon Water Blocking Primer/Finish, a cementitious waterproofer, or fix the drainage and grading outside.
How cold can Loxon XP be applied?
Down to 35°F, which is 10 to 15 degrees lower than most exterior acrylics. Air, surface, and material must all be 35°F or above and at least 5°F above the dew point, with no rain or snow expected within 2 to 3 hours and no drop below 35°F for 48 hours after. In the 35 to 45°F band, plan on 6 hours to touch and 24 to 48 hours to recoat.
How much Loxon XP do I need per square foot?
Estimate at the low end. The flat covers 85 to 110 sq ft per gallon per coat and the satin 75 to 95, and rough stucco pulls both to about 80. At two coats, a 10,000 sq ft elevation is roughly 200 to 250 gallons. Running the takeoff at the high end of the published range on a rough substrate is the most common estimating error on this product.
Can Loxon XP be thinned for spraying?
No. The reducer line on the data sheet reads Do Not Reduce. Airless application is 2300 psi through a .021-inch tip as supplied. Thinning to make it spray easier drops the applied film below the specified wet-mil range, and the waterproofing performance data applies only to material laid at that thickness.
Ask a Question
Mid-project with Loxon XP? Stuck between two cans?
Ask Robert below — every question gets a real reply, usually within a day. Specified or applied Loxon XP on a commercial elevation? Tell us the substrate, the series and sheen you ran, and what your wet-mil readings and pinhole count looked like on open block.