05/26/2026
SHOTCRETE FAILURES
Understanding the process can make or break the success of a shotcrete pool. Too many pool contractors do not understand concrete science or shotcrete.
Because of this lack of understanding, they cannot critically evaluate the practices of their shotcrete subcontractors.
Subcontractors will say “we’ve always done it this way,” or “we’ve never had a problem before.” Both may be true, however there are common bad practices that compromise the integrity of the process.
BAD PRACTICES:
1. Hands or fingers in the stream of the shotcrete or squeezing the nozzle.
This separates the aggregates from the cement paste and slows down the velocity - resulting in weaker concrete.
2. Not shooting the horizontal surfaces or coves before the walls or benches.
Failing to place the floor or coves first allows the loose trimmings from the vertical walls and benches to fall into the floors & under the steel.
If this material is still plastic, it can be VIBRATED into place. However, most of the time the wall materials have stiffened & set up, so trimmings become waste materials. It is virtually impossible to shovel out this waste from under the floor steel.
This is also why spa benches & floors are notoriously sources of reoccurring problems.
3. Pacing trimmings into benches, walls or floors.
Once the concrete has stiffened it cannot be thrown into benches, floors or walls. It is a waste product that needs to be hauled off site.
If your recently shot project looks really clean, ask yourself “where are all of the trimmings?” There should be piles of waste around the entire pool.
4. No one is using a vi****or.
Most placed concrete is not self-consolidating. Vibration is required to consolidate it & remove air pockets & voids.
Walking on this material (aka: “stompcrete”) does not consolidate it.
5. Excessive foot traffic on freshly placed materials.
Walking all over freshly placed materials - another version of stompcrete, alters the compressive value & water to cement ratios.
6. “Flashing” the floor at the end of the job.
They’re not doing you a favor - they’re cleaning out their pump & hoses in your pool floor.
The water used to rinse their hopper & hoses alters the cement to water ratio, which results in a weak crusty layer on the floor.
This is why these areas are very white in color & hollow sounding.
KNOWLEDGE IS KEY
If you don’t know the correct way to install shotcrete, you cannot hold your subcontractors accountable.
If you don’t supervise your subcontractors, they will take the path of least resistance.
