8 compatibility checks before choosing sanded or unsanded grout

At a glance

Core Rule of Thumb: Select grout from the tile requirements and exact product limits before calculating bags. Standard Formula: Joint volume equals tiled area multiplied by the repeating grid’s joint fraction and filled depth. Quick Estimate Range: Sanded and unsanded labels do not establish one universal width limit across all products. Recommended Qtywise Tool: Use the Grout Calculator for cavity geometry, then check the chosen product’s coverage or mixed yield.

Choosing sanded or unsanded grout requires more than deciding whether the joints look narrow. The exact formulation, tile finish, exposure and installation instructions control compatibility. The eight checks below put those decisions before quantity arithmetic. They compare evidence to request, not a ranked list of brands, and do not treat a generic width rule as approval for every product.

Identify the actual grout formulation

Write the full product name and technical-sheet reference beside the proposed color and package size. Traditional cementitious sanded grout, non-sanded cementitious grout and other newer formulations should not be collapsed into two interchangeable purchasing bins. Read the instructions for the actual product being offered. A supplier substitution needs its own compatibility check even when its color name looks similar.

CUSTOM’s current Polyblend Plus Sanded product page identifies TDS-360 and states a product-specific joint range of 1/8 to 1/2 inch. That is an example tied to this named formulation, not a rule for every product containing aggregate. Keep the actual package instructions and relevant current technical information with the selection record.

Read CUSTOM Polyblend Plus Sanded Grout, TDS-360 product page.

Check the accepted joint geometry in the Grout Calculator.

Measure the joint widths the product must fill

Record the planned spacing and check representative installed joints before ordering. Note narrow sections, wider variations and edge conditions separately. A nominal spacer size may not describe every finished gap. Ask the installer to reconcile the actual geometry with both the tile manufacturer’s requirements and the grout product’s stated limits before selecting a formulation.

The current Polyblend Plus Non-Sanded page describes joints up to 1/8 inch and identifies sensitive polished or glazed surfaces among its intended applications. Its stated range overlaps the sanded example at 1/8 inch. That overlap is why width alone does not settle the decision at the boundary. Surface compatibility and the full instructions still matter.

Read CUSTOM Polyblend Plus Non-Sanded Grout, TDS-369 product page.

Preserve the manufacturer’s stated units

One eighth of an inch equals 3.175 mm mathematically, while product documents may use rounded metric labels. Quote each manufacturer’s stated limits accurately and ask for clarification where a critical dimension falls near a limit. Do not quietly enlarge an allowable range by converting a rounded value back and forth or assuming another country’s product has identical instructions.

Check scratching risk on the actual tile finish

Record the tile or stone identification and finish, including any polished, highly glazed or decorative surface. Ask the tile and grout suppliers about the proposed combination. A sample tile that looks similar is weaker evidence than the actual supplied material. Keep any written compatibility guidance with the accepted product schedule and mockup record.

A non-sanded label is not a blanket promise that every surface will be unharmed by every installation method. Ask for the manufacturer’s required suitability test and use a representative mockup. Observe the finished surface under agreed lighting after the specified process. Do not extrapolate a successful test on one finish to an unrelated tile or a changed cleaning method.

Check absorption, staining and cleanup on a mockup

Porous or textured surfaces can raise a different question from scratching. Ask whether the specified tile needs a permitted pretreatment and which cleaning procedure applies. CUSTOM’s dated TDS-369 discusses absorption, possible staining and suitability mockups. Its instructions are product-specific; check the current applicable guidance before buying or introducing another sealer into the assembly.

Read CUSTOM Non-Sanded technical sheet, published August 2020.

Keep the approved mockup available as a reference for color and finish. Record the tile batch, grout, mixing basis and cleanup procedure used by the installer. A color card helps choose a color, but it does not document how the actual combination will appear in that space. Resolve an unacceptable sample before expanding the work across the installation.

Confirm where the grout will be used

Name the installation location and actual exposure: an interior dry area, shower, exterior installation or submerged application needs an explicit scope check. Avoid inferring suitability only because the product is sold for tile. Read all applicable limits and waiting periods with the installer. If chemical exposure or special cleaning is expected, ask the manufacturer for the relevant evidence.

A grout choice is only one part of a tiled assembly. It does not establish that the substrate, waterproofing or drainage design is suitable. Keep those separate approvals visible in the project record. This compatibility checklist does not authorize a shower repair or substitute for investigating movement, leakage or a failed underlying installation.

Separate movement joints and changes of plane

Identify the joints that the project detail reserves for an appropriate flexible material. The dated Non-Sanded TDS states that its grout is not for movement joints or changes of plane. Follow the actual assembly specification and current manufacturer requirements rather than treating every visible gap as a cement-grout cavity.

Do not include separately detailed sealant joints in the grout purchasing area without a suitable adjustment. Keep their product and quantity on a separate line. Ask the installer to show where each material starts and stops. A joint-width comparison between two grout products cannot resolve an omitted movement-joint detail or approve filling it with a rigid grout.

Compare the agreed ordinary-joint dimensions in the Grout Calculator.

Verify installation conditions and the accepted procedure

Have the installer confirm the applicable surface condition, joint preparation, mixing, working time and curing instructions for the chosen product. These requirements can differ even between products from the same manufacturer. Keep the relevant product documents available at the job. Do not alter water proportions or combine products to force a material into joints outside its stated scope.

For an existing installation, record old grout and adhesive occupying the joints and obtain the appropriate repair method. A nominal tile thickness is not automatically the available filled depth. The quantity worksheet can accept a verified depth, but it cannot decide that a shallow repair is suitable. Resolve that technical question before converting a small volume estimate into a purchase.

Match coverage and package data before comparing cost

After compatibility is settled, use the actual area, tile dimensions, joint width and filled depth. The Grout Calculator estimates a repeating rectangular grid’s cavity volume. It does not approve the grout or assign the same mixed yield to every bag. Enter liters per bag only when supported for the selected product; a dry bag’s weight alone is not a volume yield.

For an explicitly hypothetical geometry check, take 100 sq ft of 12 inch square tile, 1/8 inch joints and 1/4 inch filled depth. The joint fraction is 1 minus 144 divided by 12.125 squared, approximately 0.0205123. Converting the resulting cubic inches gives about 1.21 liters of joint cavity before allowance. This is geometry, not a published bag coverage claim.

Check the quantity without inventing a density

The same area is 9.290304 m², the depth is 0.00635 m, and multiplying those by the same joint fraction gives about 0.00121009 m³. That is again 1.21 liters. Keep intermediate precision and round only the displayed value. Compare the result with the manufacturer’s applicable coverage chart and resolve material differences with the supplier instead of inventing a mixed density.

Actual edge effects, varying joints and installation loss can change demand. Keep any explicit allowance separate from the base cavity calculation and round packages only after using supported product data. Compare actual local package sizes and quotations in the correct currency. UK and European readers should obtain the locally supplied formulation’s instructions rather than assume a US product example applies unchanged.

Keep the selection and order together

• Retain exact grout and tile product identifications.
• Confirm measured widths, filled depth and exposure.
• Approve the representative mockup and separate movement-joint detail.
• Keep coverage evidence, allowance and package rounding with the order.

Recheck the final geometry in the Grout Calculator after product compatibility is confirmed.