CMU Grout Lift and Pour Height Limits

THE LIFT LIMIT IS ABOUT CONSOLIDATION: grout placed deeper than it can be properly vibrated leaves voids, and a void in a grouted cell means the reinforcement is not embedded and the wall does not have the strength the drawings assume. THE POUR LIMIT IS ABOUT THE WALL'S OWN STRENGTH WHILE THE GROUT IS FLUID: freshly grouted masonry is holding back a column of liquid at roughly 140 pounds per cubic foot, and a pour higher than the wall can resist blows it out. A pour is made up of one or more lifts, so the two limits are checked separately and the lift count falls out of them. The pressure arithmetic is worth carrying because it is the whole reason for the pour limit: a five foot pour puts about five pounds per square inch on the inside of joints that are hours old, and doubling the pour doubles it. Blowouts are exactly what happens when a crew decides to grout a full storey in one go because the pump is already there, and the wall gives no warning before it goes. CLEANOUTS ARE THE PROVISION THAT GETS OMITTED AND THEN REQUIRED. Above a threshold pour height the code requires openings at the base of every grouted cell so mortar droppings can be removed and the space inspected before grouting, and they are closed only after that inspection. A wall built without them and discovered at inspection has to be opened at the base -- cutting units out of completed work -- which is far more expensive than building them in, and entirely avoidable by checking the pour height before laying. CONSOLIDATION IS A TWO-STEP REQUIREMENT rather than one. Grout is vibrated when placed and again after initial water loss, because it settles as the masonry absorbs water, and reconsolidation closes the void that leaves at the top of the lift -- which in many walls sits directly over a reinforcement lap. THE CODE LIMITS ARE ENTERED AND NO TABLE IS SHIPPED. Maximum lift and pour heights depend on the grout space least dimension, the unit type, whether the grout is fine or coarse, and whether cleanouts are provided, and the table that governs is the one in the adopted edition. This does not compute grout volume, design the wall, evaluate whether a specific wall can resist a specific pour pressure -- which depends on the units, the mortar, the joints' age and the bracing -- or address grout demand, aggregate, slump, admixtures, or self-consolidating grout, whose placement rules differ. TMS 602 as adopted, the project specification, and the inspector govern.

lifts in a pour = pour height / lift height rounded up; the fluid pressure at the base of a pour = grout unit weight x pour height, about 140 pcf for grout; cleanouts are required above a threshold pour height.

The TMS 602 grout placement limits by name -- the LIFT limit governs consolidation and the POUR limit governs the wall's resistance to fluid grout pressure. NO LIMIT TABLE IS SHIPPED: the maximum lift and pour heights depend on the grout space least dimension, the unit type, fine or coarse grout, and whether cleanouts are provided, and come from the adopted edition. TMS 602 as adopted, the project specification, and the inspector govern.

A division and a multiplication on limits the reader takes from the adopted code; no limit table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: pour_height_ft, lift_height_ft, max_pour_height_ft, max_lift_height_ft, grout_unit_weight_pcf, cleanout_threshold_ft, lifts_in_pour, actual_lift_ft, base_pressure_psf, base_pressure_psi, pressure_at_limit_psi, pour_margin_ft, lift_margin_ft

• Code limits are entered they depend on grout space, unit type, grout type and cleanoutsTMS 602 as adopted
• No wall capacity check whether a specific wall resists a specific pour depends on units, mortar, joint age and bracingthe project engineer
• Not a grout quantity volume, aggregate, slump and self-consolidating grout are separatethe project specification