Repairs
How much filler the cracks and spalls will take
Cracks, joints and broken-out patches are the line item a low quote leaves out, and they are also the only part of the job you can measure exactly before anybody buys anything. A chased crack is a prism. A spall is a shallow dish. Both convert to gallons through one number: a US gallon is 231 cubic inches.
Repair material required
1.74 gal
across 5 containers, in three different product classes
Each defect type, priced as its own product
These are not interchangeable materials, and buying one product for all four is the commonest mistake on this part of the job. A rigid filler in a moving joint tears itself apart; a flexible filler in a static crack stays soft and the coating over it prints every wheel that crosses.
| Defect | Volume | Gallons | Containers | Product class |
|---|---|---|---|---|
| Chased static cracks | 99 cu in | 0.429 gal | 1 | Rigid crack filler — a semi-rigid epoxy or polyurea |
| Movement and saw-cut joints | 60 cu in | 0.260 gal | 1 | Flexible joint filler over backer rod |
| Spalled and broken-out patches | 48 cu in | 0.208 gal | 1 | Epoxy mortar, resin gauged with graded sand |
| Low areas brought up to plane | 194 cu in | 0.842 gal | 2 | Patching resurfacer or self-levelling underlayment |
The geometry, stated so you can check it
- Cracks. Length in feet times twelve, times the chase width, times the chase depth. A straight prism, and the reason we ask for the chased dimensions rather than the visible crack.
- Joints. The same prism, but the depth is the fill depth above the backer rod rather than the depth of the saw cut.
- Spalls. Length times width times depth times two thirds, because a spall is a dish and not a rectangular hole. That two thirds is an approximation and it is stated rather than buried.
- Low spots. Area times the deepest measurement times one half, because a low area is a bowl whose depth is not uniform.
- Every one of them converts to gallons by dividing by 231. A cubic foot is 7.4805 gallons, if you prefer to work that way.
That divisor is the only fact on this page that came from outside your tape measure, and it is a legal definition rather than a coatings convention.
Statements of fluid measure shall be in terms of both the U.S. gallon of 231 cubic inches and quart, pint, and fluid ounce subdivisions thereof and SI metric liters or milliliters
What that changes for your floor Because the gallon is fixed by regulation rather than by custom, a repair takeoff is not really an estimate: measure the voids honestly and the material figure is exact arithmetic. All of the uncertainty in the answer above therefore sits in the measuring, which is why the chased dimensions matter more here than any assumption this site makes.
Joints are not cracks, and treating them as cracks breaks the floor
A saw-cut joint exists so the slab can crack where somebody chose rather than where it wants to. Filling one rigidly does not stop the slab moving; it relocates the crack to the middle of a bay, where it will telegraph straight through your new floor.
The correct treatment is backer rod pushed to a controlled depth, then a flexible filler on top. The rod sets the fill depth and stops the filler bonding to the bottom of the joint, which lets it stretch rather than tear. A joint filled deeper than about twice its width is a joint that will fail in tension.
There is a real exception: in a heavy-traffic industrial floor, joints are often filled with a semi-rigid product specifically to support the joint edges against hard wheels. That is a considered decision made with the slab's movement history in front of you, not a default.
When repairs happen in the sequence
- Prepare the slab first. Grinding after repair takes the repair off again, and grinding before repair exposes the sound concrete the filler needs to bond to.
- Cut spalls back square to sound material. Filler laid over a loose edge takes the loose edge with it.
- Chase cracks open. A surface-filled crack is a cosmetic act.
- Fill, let everything cure — 16 hours at the quantities above — then grind the repairs flush.
- Only then coat. A repair proud of the floor shows through every coat you put over it.
What the measurements you entered suggest
Nothing flagged by the numbers you entered.
Biggest swing factor The chase dimensions. Doubling the chase width doubles the filler, and people routinely measure the hairline they can see rather than the groove they are about to cut.