Preparation
Choose cleaners from step 1 + 2 do ensure you have a clean surface
How to build your basement waterproofing kit
Joints & Cracks
Choose fabric reinforcement if you have any joints and cracks to seal
WATERPROOFING
Choose the size of SEMCO Liquid Membrane that you need to complete your project
Surface Protection
If your surface has heavy foot traffic or furniture, choose a sealer to protect your waterproofing
Basement waterproofing
Build your basement waterproofing kit
Step by step
How to use Liquid Membrane for basements
Follow these steps for prep, application and cure timing based on the pool 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
• If there is constant dampness in the substrate, use Natural Shield first to mitigate the moisture. Let it fully cure first prior to applying SEMCO Liquid Membrane™ .
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
• Suitable for light foot traffic.For heavy foot traffic or vehicle traffic, we recommend using SEMCO Titan Shield Gloss.
• 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.
• Application on non porous surfaces such as metal or fiberglass : Apply thin coats as this will allow for the product to cure faster.
• 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.
• 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 my basement?
Yes-waterproofing basements is one of the most common and successful uses of SEMCO Liquid Membrane™. Applied over clean, sound, dry masonry it cures into a continuous flexible rubber membrane that blocks water penetration and airborne moisture, and homeowners routinely report leaky, damp basements staying dry through heavy rain and wet winters after two or three coats. It works on interior and exterior foundation walls, block and poured concrete, crawl spaces, and cold cellars.
How do I treat cracks in my basement wall before coating?
Fill and reinforce cracks first. Customers fill hairline cracks and seal them as they coat, use foam or hydraulic filler on larger cracks, and embed SEMCO Fabric Reinforcement into the first wet coat over cracks wider than 1/4" before coating the whole surface. This spreads stress so the crack doesn't reopen and telegraph through the membrane. One reviewer sealed a new poured-wall crack this way after cleaning with Nu-Lift and Stone Soap — no more water.
Should I apply it to the inside or the outside of my basement wall?
Both work, and each has a place. The most durable fix is on the exterior (positive, water side) of the foundation — often paired with a French drain and backfill — because it stops water before it enters the wall. But many customers can't excavate, so they successfully seal the interior (negative side) instead and report the dampness and leaks stopping. If you have the access, exterior is ideal; if not, interior application still delivers real results, and support can advise on your specific situation.
Can tile be applied on top of SEMCO Liquid Membrane™?
Yes. SEMCO Liquid Membrane™ can be applied to the substrate as a primary waterproofing layer and tile can then be installed over it with your mortar or thin-set system.
Can one paint over SEMCO Liquid Membrane™?
Yes - once fully cured you can finish over it. Customers confirm you can paint over the membrane with a water-based acrylic paint (support advises this directly), and others have carpeted or painted basement floors sealed with it. This makes it a great base layer for finishing a basement: seal first to stop moisture, then paint, drywall, or floor over it with confidence.
How much do I need for my basement, and is there a kit?
Coverage is roughly 100–250 sq ft per gallon per the recommended build, but porous block and rough old walls use more, so measure your wall area, plan for multiple coats, and buy a little extra. Many basement jobs use the economical 5-gallon pail (about $0.39–$0.43 per sq ft). SEMCOworks also offers a Retaining Wall Kit and a Kit Builder / Shop by Project tool to bundle the membrane, cleaners, and fabric, and support will happily calculate exactly what your basement needs.
Does SEMCO Liquid Membrane™ smell, and is it safe to use in an enclosed basement around a furnace or gas water heater?
It's water-based and very low-VOC (about 14 g/L), so it's low-odor and one of the few waterproofers people feel comfortable using in a closed basement — reviewers specifically chose it to apply around a gas water heater without having to vent fumes, and in crawl spaces without worrying about ventilation. Some even sprayed it with an airless sprayer and noted no bothersome smell. As with any coating, still use reasonable ventilation while you work.