As more DIY’ers and entry level contractors enter into the concrete countertop industry, standards help ensure that their work meets the level of quality produced by experienced professionals and meets market expectations. Standards provide confidence and assurance to the clients and designers who buy and specify concrete countertops.
Standards are industry guidelines set forth to ensure a common level of quality and performance. Standards are not intended to specify aesthetics, design or to control creativity.
Slab Thickness
- Nominal thickness should vary by no more than 1/16” over a 4’ length of countertop.
- Nominal thickness should vary by no more than 1/32” across a seam.
Surface Flatness
- Countertop slabs should be flat and smooth, with variations of no more than 1/16” over a 4’ length of countertop.
Edge Straightness
- Straight edges should be flat and smooth, with variations of no more than 1/16” over a 4’ length of countertop.
- Curved edges should be smooth and fair.
Edge Profile
- Edge profiles should be consistent along the length of the countertop edge, and should closely match across seams.
- Vertical edges should be square and true to the top surface.
- Corners and arrises should be clean, consistent and uniform.
Seam Tolerances
- Seam width should be consistent along the seam length with variations of no more than 1/16”.
- Seam width should be as tight as possible but should be no greater than 1/8”.
- The surfaces of adjacent slabs should be even and flush and should be flush to within 1/64” along the entire length of the seam.
Surface Quality
- Horizontal countertop surfaces in kitchen and bath countertops should not have more than 2 pinholes per square foot. In kitchens, zero pinholes is ideal for sanitation and hygiene reasons.
- Pinholes or voids in vertical surfaces are permitted as aesthetic features.
- There should be no tool marks visible on any finished surface.
- Filled voids and pinholes in the surface should be no more than 1/32” deep.
- The countertop undersides should be flat, smooth to the touch and free of drips, chips and lumps.
Surface Cracks
- Hairline cracks that may occur in the finished product are a natural characteristic of concrete. Hairline cracks do not affect the structural integrity of the concrete. Hairline cracks are defined as cracks that are less than 0.004” wide, which is the thickness of a piece of common copy paper.
Stain Resistance
- Sealed concrete should resist staining agents representative of materials found and used in the location where the concrete will be installed.
- At a minimum, sealed concrete should resist these 12 common household staining agents:
- Vinegar
- Lemon juice
- Mustard
- Coffee
- Red wine
- Vegetable oil
- Water
- Ammonia
- Bleach
- Isopropyl alcohol (70%)
- Acetone
- Dish soap
- Stain resistance falls into 4 grades, according to how long the sealer completely resists physical damage and permanent discoloration after a time period of continuous exposure to all 12 common household staining agents:
- Grade 1: 24 hours of resistance
- Grade 2: 8 hours of resistance
- Grade 3: 1 hour of resistance
- Grade 4: Sealed surface behaves similarly to bare, unsealed concrete.
- Sealed surfaces should be free of drips, streaks, ripples, bubbles or other surface flaws.
- Sealed surfaces should not delaminate, peel or bubble.
- Surface sheen should be consistent in appearance across multiple slabs.
- Sealed surfaces should be resistant to temperatures of at least 300°F for a minimum of 5 minutes.
- Sealed surfaces should not discolor or degrade from exposure to UV light or sunlight.
