Block retaining wall · SEMCO Liquid Membrane
Projects › Retaining Walls
The white on your wall isn't a stain. It's water leaving.
A retaining wall holds back saturated soil year round, so water moves through the block continuously — carrying salts out and freeze-thaw damage in. Seal the surface and the cycle stops.
A weekend, not a rebuild
Four steps. Block, concrete or timber.
A retaining wall holds back wet soil for its whole life. Sealing it is the difference between a wall that weathers and one that spalls.
Clear the efflorescence
Those white mineral deposits are the wall telling you water is moving through it. Nu-Lift lifts them; Stone Soap clears the residue and rebalances the surface pH.
Bridge the joints
Fabric Reinforcement at mortar joints that have opened, at cracks over ¼", and where the wall meets its footing.
Coat the whole face
Two coats for an exposed face, three on the buried side or on timber. Thin and even, each coat perpendicular to the last.
Cure before backfill
Dry to touch in an hour, initial cure at least 7 days — longer with thick coats or high humidity. If you’re coating the buried side, don’t backfill until it’s cured hard.
The buried side is the better side — if you can reach itCoating the soil face stops water before it enters the block, which is always more durable than stopping it on the way out. Most people can’t excavate, and coating the exposed face still works — one customer sealed a cinder block wall from the inside and called an exterior repair “a near impossible task”.
Your wall
What does your wall need?
The material decides the prep and how much the surface drinks. Tell us both and we’ll size the job.
What is the wall made of?
Rough and porous surfaces absorb noticeably more than smooth ones.
Which side can you reach?
Both work. The buried side is more durable because it stops water before it enters.
How big is the surface?
Length × height of the face you’re coating. For a planter, add the base and all four sides.
Tell us the material and the area — we’ll work out exactly what the job needs.
Untick anything you already have. Quantities are editable.
Will it work on mine?
Walls, planters and everything holding soil back.
The most common retaining wall, and the most porous. Water moves through the block and the mortar joints alike.
Prep D: Nu-Lift + Stone SoapSmoother and less absorbent, so a gallon goes further. Seals hairline cracks and form lines in the same pass.
Prep D: Nu-Lift + Stone SoapDecorative block has far more surface area than its face measurement suggests. Plan on roughly 25% more material.
Prep D: Nu-Lift + Stone SoapSleepers rot from the soil side first. Sand back, then coat — one customer applied it heavily to weathering timbers and it seeped into the open crevices.
Prep E: sand with 60-gritPermanently damp, so treat them as submerged: three coats. Customers have lined both concrete planters and stripped-back timber boxes with it.
Prep D · three coatsA wall that is leaning, bulging or losing block. That’s a structural failure and no coating fixes it — the wall needs rebuilding or proper drainage behind it first.
Real walls
Walls that stopped bleeding white.
“Sprinklers left white deposit as water was getting into my block wall.”
Used this on my retaining walls around my house as my garden sprinklers left white deposit as water was getting into my block wall. After the application I can just hose down my walls once every now and then. Makes it so much easier to maintain and gives my walls a new look as well.
“It would have been a near impossible task to repair from the exterior.”
Purchased 2 pints of this material on a whim and so glad I did. I cleaned and prepped the block wall surface. Applied 3 coats by brush and it has been six months since I applied the material and have no leaks since. The product does work — it would have been a near impossible task to have made the repair from the exterior.
“Multiple coats in one day.”
I used this to waterproof the inside of a cinder block retaining wall. It was so easy to apply. I used a roller with 1/2 nap and a cheap masonry brush for the corners. In 50 degree F it dried to the touch in about 2–3 hours so I was able to apply multiple coats in one day. I wrapped the roller and masonry brush in plastic grocery bags between coats.
“After much research and price comparison.”
So I’m installing storm water planters on a remodel job and needed to waterproof the inside of the planter. After doing much research and price comparison I purchased two 5 gal. pails. Application was straightforward and simple. I would definitely purchase again when needed. Quick shipping a major plus.
“It seeped into the open crevices easily.”
We used it to apply to our weathering landscape timbers — as they were beginning to look really bad. We put it on real heavy and it seeped into the open crevices easily, which is what we wanted. So far, we are very pleased.
“I can’t afford a retaining wall right now.”
I can’t afford a retaining wall right now, so I know moisture is going to be an issue still. Until I found this stuff. Applied it on the concrete walls and concrete foundation.
Why walls go white
Efflorescence isn’t a stain. It’s a receipt.
That chalky white bloom is mineral salt left behind after water has travelled through the block and evaporated off the face. It isn’t on the wall — it came out of it. Scrubbing it off treats the symptom and it returns with the next wet spell.
A retaining wall never gets to dry out the way a house wall does. It holds back saturated soil year round, so water moves through it continuously, carrying salts out and freeze-thaw damage in. That’s what spalls the face and opens the mortar joints. Seal the surface and the cycle stops.
The full version
Detailed application instructions.
01 Clean the wall — Prep D
You’ll need: Nu-Lift Cleaner · Stone Soap
- Remove soil, moss, loose mortar and anything flaking.
- Wet the wall, apply Nu-Lift Cleaner and work it in with a stiff bristle brush to lift efflorescence and mineral deposits.
- Rinse with fresh water.
- Follow with Stone Soap to clear the residue and rebalance the surface pH, then rinse again.
- Let it dry completely. A retaining wall holds moisture — give it more drying time than you think.
02 Reinforce joints and the footing line
You’ll need: Fabric Reinforcement · Liquid Membrane
Mortar joints move more than the block does, and the joint where the wall meets its footing moves most of all.
- Repoint anything that has failed before you coat.
- Coat the joint generously, lay Fabric Reinforcement into the wet film, press it flat.
- Wait 10–15 minutes, then coat over it to encapsulate.
03 Coat the face
- Stir the product well — pigments settle and unstirred product gives uneven color.
- ½" nap roller on the flat, a masonry brush into the joints and corners.
- Two coats on an exposed face; three on the buried side, on timber, or in a planter.
- Recoat when it holds no fingerprint. One customer applying at 50°F got two to three hours between coats and finished in a day.
04 Cure — and backfill last
Dry to touch in about an hour. Initial cure is at least 7 days — longer with thick coats or high humidity. Apply between 50–90°F, avoiding direct afternoon sun and anything over 85°F.
| CMU / poured concrete | ~200 sq ft per gallon at 2 coats |
| Split-face / rough block | ~150 sq ft per gallon at 2 coats |
| Timber & planters | ~100 sq ft per gallon at 3 coats |
| Initial cure | 7 days minimum before backfill · longer if humid |
| Temperature | 50–90°F · not in direct afternoon sun or over 85°F |
| Prep | D on masonry · E on timber |
Retaining wall questions
The ones worth asking.
Should I coat the soil side or the face I can see?
The buried side is better if you can reach it — it stops water before it enters the block. But most people can’t excavate, and coating the exposed face works: customers have sealed block walls from the accessible side and reported no leaks months later, with one calling an exterior repair near impossible.
Will it stop the white deposits coming back?
Yes, once the surface is sealed the salts have no route out. Clear the existing efflorescence with Nu-Lift first — coating over it means bonding to a layer that’s already letting go.
Can I use it on landscape timbers?
Yes, with Prep E — sand with 60-grit, no cleaner. Bare timber drinks the first coat, so plan on three coats and roughly 100 sq ft per gallon rather than 200.
What about a planter or a stormwater box?
Treat it as submerged: three coats. Customers have lined concrete planters and stripped-back timber boxes with it, including one that was leaking through failed TPO.
Does it still need a drain behind the wall?
Sealing reduces what comes through, but a retaining wall should still have drainage. If yours has none and the soil stays saturated, add a drain at the base while you have the wall exposed.
Is it safe next to planting?
It’s water-based and low-VOC at 14 g/L, and cures to an inert film. Let it cure fully before soil or water goes back against it.
My wall is leaning. Will this help?
No. Leaning, bulging or displaced block is a structural problem — the wall needs rebuilding or proper drainage first. A coating seals a surface; it can’t hold back soil.
Not sure about your wall? Call 1-833-211-2297 — the team will tell you honestly if yours needs a contractor instead.
Before you start
Additional information.
The manufacturer notes that decide whether this goes well. Most of the problems people report trace back to one of these.
Stop scrubbing the white off. Seal the wall.
Efflorescence, spalling faces, opening joints — all of it is water moving through the block. Seal the surface and the movement stops.
Size my wall