Instantly calculate masonry grout fill volume in cubic feet, bags, and total material cost for CMU block walls, hollow concrete block cells, bond beams, masonry columns, and partially grouted walls — ASTM C476 & ACI 530 / TMS 402 compliant.
Select your CMU block size, wall dimensions, grout spacing, and bag price for a complete fill estimate.
All cells filled — required for seismic, high-wind & structural walls per TMS 402.
8×8×16 in is the most common US CMU block — 2 cores per block, each ~5×5 in.
Total wall length along the face of the CMU wall.
Standard 8-in CMU wall: 8 ft = 12 courses. Each course = 8 in height.
Hollow core width inside CMU block. Standard 8-in CMU: ~5 in wide per core.
Core depth (in wall thickness direction). Standard 8-in CMU: ~5 in deep.
Standard 8×8×16 CMU has 2 hollow cores per block.
Fully grouted = every cell. Partial grouting fills only cells with vertical rebar.
Fine grout required when smallest cell dimension is under 3 in. Most 8-in CMU = fine grout.
2025 USA avg: $9–$16 per 80-lb bag (ASTM C476 masonry grout). Ready-mix also available.
Check manufacturer data sheet. ~0.45 cu ft per 80-lb bag is typical for fine masonry grout.
Masonry grout fill per ASTM C476 is a high-slump cementitious mixture pumped or poured into the hollow cores of CMU (concrete masonry unit) block walls, masonry columns, and bond beam courses to create a solid, reinforced composite wall assembly. Unlike standard concrete, masonry grout is designed to be extremely fluid (8–11-inch slump) so it flows freely around vertical rebar and completely fills the narrow cells of CMU blocks without vibration. ASTM C476 defines two types: fine grout (portland cement + sand; used when any cell dimension is under 3 inches — applies to most 8-inch CMU) and coarse grout (portland cement + sand + 3/8-inch pea gravel; used in larger cells ≥ 3 inches clear). Full grouting is required by ACI 530 / TMS 402 for seismic design categories D, E, and F, high-wind regions, and all structural masonry columns.
Fully grouted walls: Every cell filled — required for seismic categories D/E/F per TMS 402, all masonry columns, heavily loaded shear walls, and most commercial construction. Provides highest strength, mass, and fire rating. Partially grouted walls: Only cells containing vertical rebar are filled — commonly used in seismic categories A/B/C for residential and light commercial construction where full grouting is not code-required. Reduces material cost by 40–60% vs. full grouting. Bond beam grouting: Entire horizontal course filled with grout and continuous horizontal rebar — required at top of wall, at floor/roof diaphragm connections, and at regular intervals (typically every 4 ft vertically) to tie the wall together and distribute lateral loads.
The most common US CMU block — 8×8×16 inches — has two hollow cores each approximately 5×5 inches. Each block requires about 0.067 cu ft (116 cu in) of grout per core for a fully grouted wall (2 cores × 0.033 cu ft each). A standard 8-ft tall × 20-ft long wall (approximately 180 blocks) requires roughly 12–14 cubic feet of grout fill including 10% waste — about 27–32 bags of 80-lb masonry grout.
Bond beams use special U-shaped or open-ended CMU blocks that allow continuous horizontal rebar to run the full length of the wall. The entire bond beam course is filled with ASTM C476 fine grout. TMS 402 requires bond beams at the top of every wall, at floor and roof connections, and typically at every 4 feet of wall height in seismic and high-wind applications. Bond beam grout volume equals the full wall length × block height (8 in) × wall width, minus the face shell thickness deduction.
Masonry columns — typically 16×16, 24×16, or 24×24 inches built from standard CMU — must have all cells fully grouted per TMS 402 Section 6. Corner rebar (typically 4 × #5 or #6 bars) runs vertically in the corner cells, with horizontal ties at 8–16 inch spacing. A single 8-course-tall (5.3 ft) masonry column 16×16 in requires approximately 3.5–4.5 cubic feet of grout — about 8–10 bags of 80-lb masonry grout.
Masonry grout fill volume is calculated by determining the net void area of the cells to be filled (cell width × cell depth per course), then multiplying by the total height of filled cells and the number of cells per linear foot of wall. For partially grouted walls, multiply by the fraction of cells being filled (e.g., 0.5 for every other cell). Always add a 10% waste factor for spillage, block absorption, and minor variations in cell dimensions.
Standard ready-mix concrete cannot be used to fill CMU cells — it is too stiff to flow freely around rebar and into narrow cell openings, and will leave voids that destroy the composite wall action. ASTM C476 masonry grout must achieve a slump of 8–11 inches (highly fluid) so it self-consolidates without vibration. The minimum water-cement ratio is higher than structural concrete — this is intentional, because the CMU block absorbs water during the pour, effectively lowering the final W/C ratio. Never add extra water to grout on site beyond the specified mix — this reduces compressive strength and can cause segregation and cell voids.
Quick-reference table for grout fill volume and bag count by wall size for standard 8×8×16 CMU blocks, fully grouted, with two 5×5-inch cores per block. All figures use a 10% waste factor, 0.45 cu ft/bag yield (80-lb ASTM C476 fine grout), and $12/bag average 2025 US pricing.
| Wall Size (L × H) | Block Count | Net Grout Vol (cu ft) | + 10% Waste | 80-lb Bags | Est. Material Cost |
|---|---|---|---|---|---|
| 10 ft × 8 ft | ~90 blocks | 3.3 cu ft | 3.6 cu ft | 8 bags | $96 |
| 20 ft × 8 ft | ~180 blocks | 6.6 cu ft | 7.3 cu ft | 17 bags | $204 |
| 40 ft × 8 ft | ~360 blocks | 13.3 cu ft | 14.6 cu ft | 33 bags | $396 |
| 40 ft × 12 ft | ~540 blocks | 20.0 cu ft | 22.0 cu ft | 49 bags | $588 |
| 60 ft × 10 ft | ~675 blocks | 24.9 cu ft | 27.4 cu ft | 61 bags | $732 |
| 100 ft × 12 ft | ~1,350 blocks | 50.0 cu ft | 55.0 cu ft | 123 bags | $1,476 |
| 200 ft × 16 ft (warehouse) | ~3,600 blocks | 133.3 cu ft | 146.6 cu ft | 326 bags | $3,912 |
The table below summarizes ASTM C476 masonry grout type, minimum compressive strength, slump, pour method, and applicable US code standard for each common CMU wall application. Confirm grout type with the project's structural engineer — the project specifications often call out specific grout type, slump, and lift height requirements on the masonry notes sheet.
| Application | Grout Type | Min. PSI | Slump | Lift Method | Standard |
|---|---|---|---|---|---|
| Fully Grouted CMU Wall (Residential) | Fine | 2,000 | 8–11 in | Low-lift ≤ 4 ft | TMS 402 / ACI 530 |
| Fully Grouted CMU Wall (Commercial) | Fine / Coarse | 2,000–3,000 | 8–11 in | High-lift ≤ 24 ft | TMS 402 / IBC 2021 |
| Partially Grouted CMU Wall | Fine | 2,000 | 8–11 in | Low-lift ≤ 4 ft | TMS 402 §7.3 |
| Bond Beam Course | Fine | 2,000 | 8–11 in | Pour per course | TMS 402 §6.1 |
| Masonry Column | Fine / Coarse | 2,000–3,000 | 8–11 in | High-lift w/ cleanouts | TMS 402 §6.2 |
| CMU Retaining Wall (Fully Grouted) | Fine / Coarse | 2,500–3,000 | 8–11 in | Low-lift ≤ 4 ft | TMS 402 / IBC 1807 |
| Lintel / Opening Fill | Fine | 2,000 | 8–11 in | Direct pour | ACI 530 / TMS 402 |
Proper masonry grout placement technique is as important as using the correct ASTM C476 mix. The TMS 402/602 Masonry Code and Specification governs all grouting procedures in the USA. Always follow the specified pour height limits and consolidation requirements — grout poured in lifts that are too tall cannot be properly consolidated and will leave voids in the lower cells.
Low-lift grouting (≤ 48 inches per pour) is used for most residential and light commercial CMU construction — the wall is built to 4 ft, grouted, allowed to gain strength, then the next 4-ft lift is built and grouted. High-lift grouting (up to 24 ft in a single pour) is used on commercial and industrial projects where scaffold moves are minimized — it requires cleanout holes in the bottom course of each cell, inspection of cells before grouting, and mechanical consolidation by rodding or vibration every 18 inches of lift height per TMS 602.
Before grouting, all cell interiors must be inspected and cleaned of mortar droppings, debris, and standing water. For high-lift grouting, cleanout holes (minimum 3 × 4 inches) must be cut into the bottom face shell of every cell to be grouted, cleaned out with compressed air and water, then inspected by the inspector before grouting. Mortar fins projecting more than 0.5 inches into cells must be removed per TMS 602 Section 3.5B — they obstruct grout flow and create voids around rebar.
ASTM C476 masonry grout must be consolidated by rodding or mechanical vibration within 15 minutes of placement and then reconsolidated after initial settlement but before final set. For low-lift grouting, rod each cell at least 3 times after pouring each 4-ft lift. For high-lift grouting, use a small pencil vibrator (1–1.5 inch head) inserted every 18 inches of pour height. Do not vibrate within 18 inches of a previous grout stop (construction joint) to avoid disturbing the partially set grout below.
Authoritative ASTM, TMS, ACI, and industry references for masonry grout fill in the USA
ASTM C476 is the standard specification for grout used in masonry construction in the USA — covering fine and coarse grout mix proportions, compressive strength requirements (minimum 2,000 PSI), aggregate gradation, slump, and testing methods for all CMU wall, masonry column, bond beam, and lintel fill applications.
View ASTM C476TMS 402 / ACI 530 "Building Code Requirements and Specification for Masonry Structures" is the primary US masonry design code governing grouting requirements, grout lift heights, cleanout requirements, partial vs. full grouting specifications, masonry column design, and seismic grouting requirements for all CMU construction in the USA.
View TMS 402The National Concrete Masonry Association (NCMA) publishes comprehensive Technical Bulletins covering CMU grout fill design, low-lift and high-lift grouting procedures, cleanout hole requirements, grout consolidation methods, and block grout volume tables for all standard CMU sizes used in US construction.
View NCMA TEK Notes