Custom Building Products Grout Coverage: Prism, Polyblend Plus, Fusion Pro

By Shakeel Muzaffar, reviewed by Prof. Dr. Khalil Mudassar, PhD · Last updated 2026-10-04

Here is the one thing that trips people up with Custom Building Products grout. Prism is lightweight, so its 17 lb box covers the same floor as a 25 lb bag of conventional grout. A generic grout calculator does not know that, so it tells you to buy about 1.6 times too much Prism.

Why Does Prism Need Fewer Pounds Than Conventional Grout?

Prism needs fewer pounds because it is a lightweight grout. Custom’s data sheet (TDS-128) states that a 17 lb box of Prism covers the same area as a typical 25 lb bag of conventional grout, and calls the product about 32% lighter than typical grouts.

That weight gap is the whole trap. Most generic tools estimate grout by joint volume, then multiply by a conventional density near 120 pounds per cubic foot. Prism fills the same joint volume but with less mass, so the pound estimate runs high.

The size of the error is easy to state. A conventional sanded grout works out to about 0.062 pounds per cubic inch of joint. Prism works out to about 0.042. Divide one by the other and Prism uses roughly 0.68 times the weight, which means a conventional-weight estimate is about 1.6 times too heavy for Prism.

The practical fix is simple: pick Prism by name in the Custom grout calculator so it uses Prism’s own lightweight figure, not a generic default. For the general joint-volume method behind any grout estimate, see our guide on how much grout you need for tile.

How Is Each Custom Grout Sold and Measured?

The short answer: cement grouts are sold by weight, while ready-to-use and epoxy grouts are sold by the unit. That changes how you read coverage for each one.

Prism and Polyblend Plus are sanded cement grouts you mix with water, so their coverage is driven by pounds per joint volume. Fusion Pro comes pre-mixed in a pail, and CEG-Lite is a two-part epoxy kit, so both publish coverage per container instead of per pound.

The table below sets the four verified Custom products side by side. Every figure comes from Custom’s current data sheets, read on 2026-10-04.

Classic Polyblend Sanded still exists, but its current chart was not confirmed for this guide. Treat it as a custom entry and enter your own figure if you use it.

What Coverage Should I Expect From Prism and Polyblend Plus?

Expect the same coverage chart from both, because Prism’s 17 lb box and the Polyblend Plus 25 lb bag publish identical square footage cell for cell. The difference is weight, not area.

Coverage depends on tile size and joint width, so a single number never fits every job. These rows come straight from Custom’s charts for common floor tile.

Two points matter for the joint range. Prism is rated for joints from 1/16 inch up to 1/2 inch. Polyblend Plus is rated from 1/8 inch to 1/2 inch, so for very thin joints below 1/8 inch you would step down to a non-sanded grout instead.

To size a real room, enter your tile and joint into a product-aware tool so it reads the right figure for you. If you still need the tile count first, our tile calculator handles that step.

How Do Fusion Pro and CEG-Lite Coverage Work?

Both are sold by the container, so you read coverage per unit rather than per pound. You pick the row for your tile and joint, then count how many pails or kits the area needs.

Fusion Pro is ready to use and comes in a 1 gallon pail, with a 1 quart pail in select colors. As a rough guide, 12 x 12 x 3/8 inch tile with a 1/8 inch joint covers about 199 square feet per gallon. A quart covers roughly a quarter of a gallon.

CEG-Lite is a two-part epoxy sold as a unit kit of about 9.5 pounds. The same 12 x 12 x 3/8 inch tile with a 1/8 inch joint covers about 187 square feet per kit. The larger kit (with a second Part A) covers double every value.

Both products handle joints from 1/16 inch to 1/2 inch. Fusion Pro is not rated for pools, steam rooms, or other submerged use, so an epoxy like CEG-Lite fits those harder jobs.

Why Do Generic Calculators Over-Order Prism?

Generic calculators over-order Prism because they assume one conventional weight for all grout. They estimate the joint volume correctly, then convert it with a density meant for standard grout, which is heavier than Prism.

Picture a 200 square foot floor that needs about 1.5 cubic inches of grout per square foot. A conventional-weight tool would bill that at roughly 0.062 pounds per cubic inch. Prism actually fills it at about 0.042. The tool’s pound total lands about 1.6 times above what Prism really needs.

That gap is real money and leftover boxes. The fix is not a hand correction; it is choosing the product. When a calculator knows the product is lightweight, it applies the lighter figure automatically.

Custom Building Products Grout: Frequently Asked Questions

Sources and Further Reading

For more home-improvement tools, browse our construction calculators.

Educational estimate, not professional construction advice; follow the manufacturer’s current data sheet; coverage varies with tile size, joint width and mixing. Not affiliated with any brand; trademarks belong to their owners. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated October 4, 2026.