Foundation Crack Injection Problems and How to Fix Each One

Injection problems almost always show up in the paste or at a port, not in the foam itself. Each fix below follows the kit’s instructions and the American Concrete Institute’s crack injection bulletin (opens in a new tab).

Which injection problem do you have?

Find your symptom, then jump to its section. The table gives the short version.

Why did my injection ports pop off?

Ports pop off when the paste holding them isn’t hard yet or when the foam is pushed in too hard. ACI says the paste and port adhesive must have properly cured so they can sustain the injection pressures (opens in a new tab), and warns that higher pressure has to be managed with care to prevent a blowout of the ports.

Close the valve on the hose. Scrape the old paste off the port and the wall, mix a small fresh batch, set the port again with paste mounded around its base, and wait until it’s fingernail hard before you start on that port again.

To keep it from happening, wait the full cure time for your kit and squeeze slowly. The kit’s instructions say hairline cracks need 3 to 4 minutes at each port, and that patient, low-pressure injection is the secret to a good repair.

Why is foam leaking from the crack through the paste?

Foam leaking from crack openings in the paste means the paste has a thin spot, a pinhole or a crack. Common causes are paste spread too thin, paste worked into the crack instead of over it, or a seal that cracked before you injected.

ACI notes that a temperature change between pasting and injecting may cause the cap seal to crack (opens in a new tab), and that it must be repaired before injection. Close the valve, wipe off the wet foam, paste over the leak, and let the patch harden before you go back to that port.

Prevent it by laying the paste 1/8 inch thick and 2 inches wide, as the kit’s instructions say, and mounding extra around each port. If the crack is wider in spots, the paste can sink in; see the next section.

Why is the surface paste not sticking to the wall?

Surface paste not sticking almost always means the wall is damp, dusty or still coated. The kit’s instructions call for wire brushing off loose concrete, efflorescence, paint and coatings 1 to 2 inches on each side of the crack, wiping off the dust, and pasting onto a dry surface.

If the wall is wet, the instructions say to wait a few days, or dry the strip with a heat gun, a hair dryer or oil-free compressed air. The two pastes behave differently on a damp wall:

• Epoxy paste is listed as moisture insensitive and cures in damp conditions, though the kit still says not to apply it to wet surfaces.
• Peel-off paste won’t cure on a damp or wet surface at all, so it’s the wrong pick for a wall that never dries out.

If your wall stays damp, the peel-off vs epoxy paste comparison explains which kit to use. A crack that’s actively running water needs the flow stopped first; the leaking crack guide covers that.

What if the paste sinks into a wide part of the crack?

The paste is meant to bridge the crack, not fill it. The foam maker’s data sheet says a wide crack may need its surface sealed with hydraulic cement or an epoxy gel before injection.

A crack wide enough for the paste to sink into may be over 1/4 inch, which is the point where this site recommends an engineer look at it before you seal it.

Why is the foam not coming out of the next port?

Either a port is blocked or the crack is too tight for the foam to travel quickly. The water flush in the kit’s instructions is the test: water poured into the top port should come out of every port below, and a port that stays dry is blocked by paste or sits off the crack.

If the flush showed every port clear, the crack is just tight. Keep squeezing slowly: the kit’s instructions say small or hairline cracks need 3 to 4 minutes at each port, and the peel-off kit’s instructions suggest warming the cartridge in a pail of hot tap water for 15 to 20 minutes so the foam flows into hairline cracks more easily.

If foam still won’t show after a few minutes, cap the port you’re on and move the hose up to the next one. The foam maker’s data sheet says to come back after a few ports and inject all of them a second time, which picks up any section the first pass missed.

What if you run out of foam partway up?

Cap the ports you’ve done and leave the rest. Fresh paste and ports go on later, and the kit sizing guide helps you pick the right amount for the length left.

The foam maker’s data sheet estimates 10 to 21 ounces of foam per 8 foot crack in an 8 to 10 inch wall. Wider cracks and voids inside the wall take more.

Why does the crack still leak after injection?

The crack wasn’t completely filled, or water is still piling up against the outside of the wall. Both are fixable.

For gaps in the fill, inject a second time. The foam maker’s data sheet says some ports take more foam on a second pass, which fills and densifies the crack; on a repair that has already cured, set new ports through fresh paste where it leaks. Check the ends too: a crack that keeps going past the top or bottom port needs a port there.

Then look outside. Gutters that overflow, downspouts that drain beside the wall and soil that slopes toward the house all push water at the foundation, and a sealed crack sends it to the next weak spot. The why repairs fail guide covers more of the reasons a fix doesn’t hold.

Why won’t the foam cure in cold weather?

Cold slows both the paste and the foam, and the kit’s instructions don’t give a minimum temperature for the foam. Do the job in a heated basement, with the kit stored indoors beforehand.

The peel-off paste’s data sheet says to condition the material to 65°F to 85°F before use. Its time to tack-free stretches from 25 to 30 minutes at 73°F to 1 to 1 1/2 hours at 40°F, so a cold wall means a longer wait before injecting.

The foam’s safety data sheet says to store it between 60°F and 85°F, and that frozen material must be thawed thoroughly and mixed until uniform. Warming the cartridge in hot tap water before use helps it flow. The cold weather guide covers working on concrete in the cold more generally.

Which kit should you use for a second try?

The same kit type usually works, done slower and with the paste fully hard. If the paste wouldn’t stick because the wall stays damp, switch to the epoxy paste version, which cures in damp conditions.

For several cracks, or one long one, the 30 ft kit (epoxy paste or peel-off) covers about 30 feet. The full step-by-step method is in the foam injection guide, and the rest of the foundation topics are on the foundation cracks hub.

Once the crack stays dry, the sealing after crack repair guide explains why an injected wall doesn’t need a sealer.