How to build your retaining wall waterproofing kit

1

Preparation

Pick cleaners from step 1+2 to prepare your wall.

2

Waterproofing

Select size and color of SEMCO Liquid Membrane needed for your project.

Customize Your DIY Kit

Retaining Wall waterproofing kit

Choose the setup that best matches your retaining wall surface and waterproofing needs. Then follow the simple preparation and application steps below for a successful, long-lasting result.

Step by step

How to use SEMCO Liquid Membrane for retaining walls

Follow these steps for prep, application and cure timing based on the wall surface you are coating. The goal is a clean substrate, even coverage and enough cure time before water exposure.

1

Prepare your surface and Gather your materials

• For concrete or brick surfaces we recommend our Preparation D in order to remove any mineral deposits or efflorescence from the surface. For this you will need the following cleaners : Nu-Lift Cleaner and Stone Soap
Ensure your surfaces are fully cleaned and dried. Gather all the products and tools needed for your project.

Helpful Tip

If you need assistance with which cleaners are needed for the Prep, feel free to use our live chat or call us!

2

Fabric Reinforcement

If you have any cracks wider than 1/4", a Fabric Reinforcement is needed to bridge the crack. Any cracks smaller than 1/4" width, SEMCO Liquid Membrane™ can be applied over it. To apply the Fabric Reinforcement, apply a generous coat of SEMCO Liquid Membrane™ over the crack. Put the Fabric Reinforcement on a press it flat, after 10-15 min apply another coat of SEMCO Liquid Membrane™ over the Fabric Reinforcement to encapsulate it. Let it dry to the touch before applying SEMCO Liquid Membrane™ over the entire surface.

3

Masking

Mask off areas that are not receiving any coating. Remove masking tape before material has fully cured.

4

APPLYING COAT

Use a 1/2" nap roller. Allow any pre-treated areas to fully dry. Apply a thin coat (0.015 inch per coat) of SEMCO Liquid Membrane™ with brush or roller over substrate including pre-treated areas. Once you can walk on the surface and not get any residue on your shoe or feet or cannot leave a fingerprint impression it is ready to re-coat. Apply another thin coat of SEMCO Liquid Membrane™ in an alternate direction over the first coat of SEMCO Liquid Membrane™. Let topcoat dry to the touch, approximately 1–2 hours at 70 °F (21 °C) and 50% RH. When last coat has dried to the touch, inspect final surface for pinholes, voids, thin spots or other defects.SEMCO Liquid Membrane™ will dry to a lighter color when it’s dry to touch. Use additional SEMCO Liquid Membrane™ to seal the defects. Required total thickness is 0.03 - 0.04 inches for non submerged applications.

5

Curing Time

Curing time depends on temperature, humidity and airflow, however typically initial cure is within 6 - 7 days as per specific product recommendations.

6

Additional Information

• For clean up use warm water to clean brush or roller right after use.
• For optimal bonding we highly recommend preparing the surface as mentioned above for best results.
• Stir up the product well before use in order to mix up the color pigments.
• Avoid application in direct sun light in the afternoon or temperatures of over 85F as it might cause the product to dry too fast before it can adhere to the substrate
• It can not be applied to wet substrates or substrates still containing moisture, else it will not cure correctly and stay tacky. Max. rest moisture in substrate can be up to 3%. If you are unsure about the moisture content, have it measured prior to application.
• Cure times are displayed in our curing chart. However if coats have been applied too thick, the surface might feel tacky. This is a sign of trapped moisture. If you have left over product, apply a very thin coat over the entire surface. The surface needs to be fully cured and hard before permitting water.
• A slight color change may occur when being in contact with water when the product has not fully cured yet. This however will not affect the performance of the SEMCO Liquid Membrane™.
• It is always advisable to apply a small test patch in an inconspicuous are to ensure adequate adhesion prior to full application.
• If you have multiple containers of SEMCO Liquid Membrane™, we highly recommend to either mix them together or use one container for the last layer to get color consistency.

SEMCO Liquid Membrane FAQ

Can I use SEMCO Liquid Membrane™ to waterproof a retaining wall?

Yes — retaining walls are a common and successful use. Customers coat cinder-block and concrete retaining walls to stop water wicking through and to prevent damage, and report easy application with a roller and a masonry brush for the corners. It cures into a flexible rubber membrane that seals the porous block and mortar joints where water gets through.

Which side of the retaining wall should I coat — the soil side or the exposed face?

Whenever you can reach it, coat the soil (water) side before backfilling, because stopping water on the source side keeps it out of the wall entirely — this is the ideal for new builds. If the wall is already backfilled and you can only reach the exposed face, coating that side still helps block water wicking through and the resulting efflorescence, as customers who sealed the accessible face report. For a new or exposed wall, treat the water side; for an existing wall, seal what you can access.

Will it work on block, cinder-block, and poured concrete retaining walls?

Yes — SEMCO Liquid Membrane™ bonds to CMU/cinder block, poured concrete, and similar masonry. Block is porous and thirsty, so plan on solid coverage across the face and mortar joints.

Can I use it on planter boxes and raised garden beds?

Yes — waterproofing the inside of planter boxes and raised beds is a popular use, including commercial stormwater/bioretention planters. Coat the interior so water and soil moisture don't leak through or degrade the structure; one customer stripped a leaking TPO-lined planter back to wood and sealed it with the membrane. Once fully cured it forms an inert barrier suitable for planters.

How many coats does a retaining wall need?

Apply a minimum of 2 coats, and 3 coats on porous block or problem walls. Reviewers typically report two to three coats giving full coverage and a lasting seal. Let each thin coat cure before the next for the strongest membrane.

Can I backfill and add drainage after coating the wall?

Yes — coat the soil side, let it fully cure, then backfill. For best long-term performance pair the membrane with proper drainage (gravel backfill and/or a drain) so water doesn't sit against the wall under pressure. The membrane seals the wall; drainage relieves the water load behind it — together they give the most durable result.

Is it safe to use on garden beds and planters where I grow plants?

Once fully cured it's an inert, VOC-free membrane — the same formula is certified safe for fish, plants, and potable water after cure, which is why it's used to line planters and beds. Allow the full cure before adding soil and plants. If you're growing edibles or have a sensitive application, contact support to confirm the right build and cure for your situation.

How much do I need, and is there a kit for retaining walls?

Coverage is up to 250 sq ft per gallon at the recommended build, but porous block uses more, so measure the wall, plan for 2–3 coats, and buy extra. SEMCOworks offers a dedicated Retaining Wall Kit that bundles the membrane with cleaner and fabric. Support will calculate exactly what your wall needs.