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RadonSeal Plus Instructions

RadonSeal Plus Deep-Penetrating Concrete Sealer is a non-toxic, ZERO VOC, Solvent-free, nonflammable, no odor, no noxious fumes, reactive-based concrete sealer formulated to penetrate and seal the capillaries and pores of indoor and outdoor poured concrete, concrete blocks, and cementitious building materials. RadonSeal Plus works by penetrating through the surface and deep into the matrix of concrete. Chemically reacting, strengthening, and permanently sealing concrete.


RadonSeal Plus is recommended for indoor and outdoor poured concrete surfaces, concrete blockscinder blocks, limestone, sandstone, and stucco. 

  • Indoor Poured Concrete: Older than 20-years old.
  • Outdoor Poured Concrete: Older than 2-years old.
  • Stucco
  • Limestone

* RadonSeal Plus is recommended for older concrete, but can be used on concrete less than 20-years old. For concrete less than 20-years old, RadonSeal Standard is recommended.


Poured concrete*, concrete block, and cinder block basement walls. Basement floor, crawlspaces, and slab-on-grade construction. Outdoor concrete sidewalks, pool decks, driveways, patios, parking lots, garage slabs, pools, water features, warehouse floors, decking, stairs, concrete fish ponds, and carports.

*Since RadonSeal relies upon a reaction with Portland cement, its effectiveness on thin concrete (less than 3″ thick) can vary. Thin concrete slabs are more common for older homes (early 20th century) and older crawlspaces.


Stamped, colored or stained concrete, polished concrete floors, modified hydraulic cement, concrete levelers, fiber-reinforced concrete, outdoor split face or lightweight blocks, bricks, pavers, chemically-modified concrete.


  • Poured Concrete: 200 sq. ft. per gallon.
  • Concrete Blocks: 100 sq. ft. per gallon.
  • Cinder Blocks: 80 sq. ft. per gallon.
  • Stucco: 200-250 sq. ft. per gallon.
  • Limestone 175-225 sq. ft. per gallon.

Surface Conditions

Concrete should be DRY prior to application. Concrete may require several days to dry after heavy rain or pressure washing. Avoid rain for 24 hours after sealer application. Ambient air and surface temperatures must be above 40o F during the application and for 72 hours after. Avoid applying to hot surfaces in direct sunlight, or in strong winds and excessive humidity. New concrete should be allowed to cure for at least 28 days.

Why Wintertime is the Right Time to Seal Indoor Concrete

Surface Prep

Surfaces must be clean, bare and porous. Vacuum or blow off excessive dust and loose particles. Mask surfaces not intended to be sealed. Product will etch glass and metal. Remove paints, sealers, curing compounds, adhesives, oil, grease, mold, efflorescence and other contaminants that might interfere with the penetration of the sealer. The surface must be porous enough to readily absorb the sealer. Hard-troweled concrete surfaces require chemical etching or mechanical abrasion to increase porosity. Use PowerEtch Concrete Etcher & Cleaner to obtain a proper surface profile.


Recommended! Concrete varies greatly in composition, finishing techniques and surface porosity. Apply RadonSeal Standard to a small test area to confirm sealer penetration into the concrete, surface suitability, and aesthetic.

Applying RadonSeal Plus

Apply using a hand-pump sprayer equipped with fan tip nozzle (recommended). Alternatively, a paint roller can be used if spraying is not feasible. RadonSeal Standard is applied in two wet-on-wet applications.

  • STEP 1: Agitate container thoroughly before use.
  • STEP 2: Using the pump sprayer, mop, or roller lightly dampen the concrete surface with water to help improve sealer penetration.
  • STEP 3: Spray RadonSeal uniformly to the surface, maintaining a continuous wetting film.
  • STEP 4: While the concrete is still damp, apply a lighter second application to the surface about 30 minutes after the first application. For concrete blocks, apply three applications.
  • Concrete Floors: Moderately rinse treated surfaces with water and scrub with a bristle broom 30-minutes after the final application. DO NOT OVER APPLY. Avoid pooling or excessive rundown. Roll, broom, or brush away puddles.


Rinse tools with water. Remove overspray with a wet towel before it dries. Dispose of unused material and empty containers in accordance with local regulations.


Treated surfaces will begin to appear dry in 1-4 hours. Avoid foot and vehicular traffic until dry.

Applying Paints & Coatings

Wait 10+ days before applying paints, coatings, adhesives, or patch repair compounds. As RadonSeal begins to react and expand inside the concrete it may purge dirt, loose minerals, salts, and efflorescence to the surface for several days after application. Clean purged contaminants and efflorescence by mechanical or chemical means when necessary.