Can You Seal Concrete To Make It Waterproof?

Can You Seal Concrete To Make It Waterproof

One of the most compelling reasons to use a concrete sealer is to help improve the water-resistance of the slab. While many manufacturers and distributors claim their products will waterproof your concrete, there is no way to guarantee this. 

If you read about such a guarantee, the company is not being entirely honest with you. Certain products offer better odds of water resistance, but no product can guarantee that their product will entirely waterproof your concrete for life.

Once you ignore the grandiose claims of most companies, you can start to figure out which type of concrete sealer offers the best level of protection from water. There are two types of sealers: topical and penetrating. 

The topical sealers will leave a film on the surface of the concrete, but they will not give your concrete as much protection from water and other moisture. For one, water can seep into the material from underneath, travelling through the concrete to cause the protective films to bubble and flake. These surface sealers are more like raincoats for your concrete, offering only minimal protection.

The better option to improve water resistance would be the penetrating concrete sealers. Silanes, siloxanes, silane/siloxanes, silicones and silicate/silicates will lock out water and other harmful moisture. 

Once your concrete is protected from excessive water damage, you don’t have to worry about problems like mould and mildew build-up, as well as the dampness and mustiness that can plague unprotected basements. 

Increased water resistance also improves the structural integrity of the concrete, as water can leech from the material vital minerals crucial to its strength and durability. If water damage is something you want to prevent, you should use a penetrating sealer, which gives you the most comprehensive protection.

How to Waterproof a Concrete House

Can You Seal Concrete To Make It Waterproof

If you’re building a concrete foundation or larger parts of your home involve concrete, you may want to consider waterproofing the concrete itself so that your rooms remain nice and cozy. That being said, a true concrete house is probably more waterproof than any other common type of structure, to begin with, and only cracks, joints, or window and door openings should require attention. This article provides more information on how to get started with waterproofing and which waterproofing techniques you might consider. Planning for a new look for your house? Look no further!  MJS Construction Group  is here to help in your home builders.

Prepping Your Concrete

Determine if your concrete house needs waterproofing. Core-formed concrete, precast concrete panels, and ICF, or Insulated Concrete Form wall construction is essentially more waterproof than most other construction methods, to begin with, meaning that it rarely needs additional waterproofing attention. That being said, the exterior walls of prefabbed concrete are often coated more for appearance than for weatherproofing.

  • If you think your structure may need waterproofing, get a general contractor you trust to give you advice. They may suggest applying a liquid membrane and not much else or suggest filling up any cracks or joints instead of staging an elaborate waterproofing production.

Prepare the walls for the coating you have selected. If you decide to go ahead with waterproofing, nearly any technique you use will require your concrete walls to be in good standing. This means:

  • Caulking — to fill any expansion joints or larger cracks up to 1⁄4 inch (0.6 cm), with high-quality polyurethane caulking.
  • Concrete patching — to fill any joints larger than 1⁄4 inch (0.6 cm), ensure the concrete patch is completely dried before proceeding.
  • You are grinding — smoothing out any rough, uneven concrete so that your waterproofing membrane or slurry has an even surface to adhere to.

Thoroughly clean the surface of your concrete before waterproofing. With a stiff brush, some TSP (trisodium phosphate) and some water, wash away any loose material, oil, or dirt still clinging to the concrete. Most membranes like a clean surface to adhere to. Let dry before proceeding.

Choosing Your Waterproofing

Use a liquid membrane for quickness and economy. Liquid membranes are usually polymer-based coatings that can be sprayed, troweled, or rolled onto concrete directly. They have the advantage of being quick to apply and are relatively low in cost. Follow manufacturer’s instructions on how to apply.

  • The disadvantage of liquid membranes is that they don’t offer even coverage. Even if you shoot for 60 mm of coverage, the minimum recommended thickness. It’s hard to achieve that consistently.

Use a self-adhering sheet membrane for consistency. Self-adhering sheet membranes are large, rubberised asphalt membranes that you peel and place directly onto the concrete. Sheet membranes boast even thickness but are more expensive (in both parts and labour) than liquid membranes and can take some time to get used to.

  • Self-adhering sheet membranes are extremely sticky. It would help if you were very diligent about peeling the membrane to expose the sticky side because it will stick to anything it comes in contact with, and it’s virtually impossible to un-stick it once it is laid.
  • Be sure to pay special attention to how sheet membranes overlap, as improper installation can result in leakage. Make sure that lap joints are properly cut and that a bead of mastic is run down every lap joint that’s spaced within one foot of a corner.
  • Sheet membranes need at least two people to install. Installing them by yourself is a sure recipe for a poor job and creates a lot of needless frustration for yourself.

Try out EIFS or exterior insulated finish systems. EIFS offers a durable, attractive, and fairly simple coating to the outside of concrete walls, doubling as insulation and waterproofing. For a stucco-like finish, an EIFS finish coat can be applied directly to the concrete, filling any voids, floating out minor irregularities, and creating a good moisture-resistant surface.

  • EIFS are applied with a trowel and come in 5 gallons (18.9 L) buckets premixed and tinted to your preferred colour. Float it off with a Styrofoam block or rubber float to create a uniform surface and texture. Other EIFS products may be sprayed, brushed, or rolled on with a paint roller.

Try using cementitious waterproofing. Cementitious waterproofing, aside from having a moniker that takes a mouthful, are easy to mix and easy to apply. Buy them from your local masonry supply store. Mix them with an acrylic additive for a better bond, and then apply with a long-handled brush for ease. The downside to cementitious waterproofing is that it doesn’t have elasticity, making it prone to cracking over longer periods.

Opt for sodium bentonite if you want to use a non-polluting, “green” method of waterproofing. Sodium bentonite is used in many city dumps to prevent liquids from leaching into the underlying soil. It is essentially clay and will act as a good waterproofing agent if you’re concerned about leaving a human footprint. Bentonite also has the advantage of being able to cover smooth as well as coarser surfaces.

Finishing Up and Other Considerations

Know which walls to apply to waterproof too. They decide which walls to waterproof and which ones to forgo can save you time, money, and headache. Here’s a water-clad rule for which walls to waterproof: Waterproof any walls with soil on one side and habitable space (including crawl space) on the other. Here are some other tips to consider:

  • If the site or the area is especially wet (think Seattle or the jungle), you may want to waterproof all walls.
  • Extend the waterproofing at least 1 foot (0.3 m) from any wall or surface that does need waterproofing to any that doesn’t. You want a little bit of a buffer, to be sure.

Apply the finish system you have selected to the wall according to the manufacturer’s directions. Depending on the method of waterproofing you use, the manufacturer will have different suggestions and best practices. Consult the instructions of whatever product you are using, or consult a GC for best results.

Apply a suitable roof sealer to your roof if you have a cast in place concrete roof. This is an unusual situation, but there are homes with a cast in place concrete roof systems, and typically, roofing cement and fibre-reinforced roll roofing are applied to the roof to prevent water intrusion.

  • If the house doesn’t have sufficient slope to allow water to drain off the roof in a rain event, you may have to apply tar or a synthetic waterproofing membrane directly to the concrete or use a seamless rubber roofing system. These products are more suitable for professional contractors to use.

Remember to allow for proper drainage in addition to waterproofing measures. Waterproofing won’t do much if the water that jets off the walls doesn’t have a good place to drain. Consult with an expert about building a perimeter footing drain, under drainpipe system, or even a sump pump for heavy-duty water relocation. If it’s a concrete basement, you’re trying to drain. Finding the right townhouse builders  is an important decision. Check out our range of the best home design constructions at MJS Construction Group.

The Right Way to Seal Concrete

Can You Seal Concrete To Make It Waterproof

Concrete is one of the most popular construction materials around, and for a good reason: It’s affordable, structurally sound, and versatile enough to use for everything from garage floors and retaining walls to kitchen countertops and decorative objects. 

While sturdy and durable on its own, it does require some protection, such as a silicone-based surface sealant like Quikrete’s Concrete & Masonry Waterproofing Sealer, to waterproof the surface and keep it looking freshly poured. Without this important finish to any concrete project, all your hard work will be more susceptible to damage. 

Moisture and temperature fluctuations can cause cracks in exterior concrete over time, while everyday wear and tear can stain and scratch interior concrete. Fortunately, an easy, early-on application will go a long way toward safeguarding concrete from these stresses. Keep reading to learn how to seal concrete with quality products so you can rest easy that your finished project will keep on looking fresh for years to come.

Serious Surface Coverage

Wait at least 30 days before sealing a new concrete surface—whether indoors or out—so that it has time to cure first completely. For the best results, the concrete surface should be clean and dry. 

That means no rain should be in the week’s forecast if you’re working outdoors on a patio, bench, or sidewalk. (You’ll also want to wait until you’re certain that the temperature will stay between 50 and 90 degrees Fahrenheit.)

Apply Quikrete’s Concrete & Masonry Waterproofing Sealer using a brush, a roller, or a garden sprayer. No mixing is necessary; the liquid sealer comes ready to use in one- and five-gallon containers. Coat the surface with enough sealant to evenly saturate the concrete, but not so much that it pools. 

One gallon will cover approximately 100 to 200 square feet, depending on whether your concrete mix skews porous or smooth (as, for example, countertop mixes tend to be). More porous surfaces require more sealant to coat fully. Though the concrete will naturally absorb the sealant and its waterproofing properties, the sealant will not change the look of the slab.

For added protection, apply a second coat 10 minutes after finishing the first coat before it has a chance to dry. Two coats of the Concrete & Masonry Waterproofing Sealer are sufficient for penetrating the surface of the concrete. For exterior applications, these two coats can last up to 10 years before resealing is necessary. Interior applications, on the other hand, which are not subject to UV rays or temperature fluctuations, should not require future resealing.

Suppose you’re treating a concrete countertop or tabletop to protect it from acidic spills like vinegar, which can cause discolouration, follow up with a food-safe wax, such as carnauba. Apply this according to the package’s instructions to create a sanitary barrier between the sealed concrete and your food so the surface will be suitable for meal prep.

Sealing Expansion Joints

While you won’t see it so much on indoor projects, virtually every large concrete surface outdoors—be it a driveway, sidewalk, or patio—is separated into smaller sections by pre-cut expansion joints. 

These joints permit the concrete to shift imperceptibly at these predetermined points to accommodate any expansion and contraction that result from temperature fluctuations or shifting ground. 

These forces could otherwise cause a single large slab to split at random points. You’ll need to seal these joints, too, either before or after you seal the surface, using a high-quality product like Quikrete’s Polyurethane Self-Leveling Sealant to minimise your concrete’s exposure to water.

Again, choose a day when the outdoor temperature is between 40 and 85 degrees and rain is not in the forecast. Ensure that the joints are clean and dry before applying the sealant: You can use a stiff-bristle brush to sweep pebbles and debris from the joints, but if oil or grease is present, use a product like Quikrete’s Concrete and Asphalt Cleaner to remove the residue before proceeding.

Press Quikrete’s Backer Rods—compressible foam rods specifically designed for use in joint and crack sealing—into any joints wider than ½ inch and leave approximately 1/8 inch of space above the backer rod for the sealant. 

For the sharpest and cleanest lines, mask off both sides of the expansion joint with painter’s tape so that you fill only the joints. Then, use a caulk gun to dispense the sealant evenly in the crack from one end to the other. 

Force the sealant deeply into the joint. Take care not to leave gaps along the edges, but don’t use so much that the sealant forms a bead above the surface of the concrete. After applying the sealant, while it is still wet, carefully peel away the painter’s tape to reveal perfectly straight lines of sealant.

Stop Cracks in Their Tracks

Over time even properly sealed exterior concrete surfaces and their expansion joints, whether on porches, steps, or slabs, can develop cracks. The sooner you seal a crack, the better: Left untreated, cracks can grow larger, requiring more difficult repairs. 

For a waterproof fix, the sealant must adhere tightly to the concrete yet stretch without pulling away if the concrete shifts again. Quikrete’s Polyurethane Concrete Crack Sealant won’t sag in the crack, and it can stretch up to 700 per cent while maintaining a strong bond—plus, its grey shade closely matches the colour of bare concrete so that the repairs won’t stand out like a sore thumb. Got many cracks to fill? Use this handy online calculator to determine how much sealant to purchase.

Good crack preparation is the key to a successful repair. In addition to starting with clean and dry concrete on a day with temperatures between 40 and 95 degrees, you’ll also need to prepare the crack for best adhesion:

  • If the crack is narrow, use a hammer and chisel to open it to approximately 1/4 inch wide, creating a “V” in the concrete. Brush away all debris from the crack with a stiff brush or vacuum it out with a shop vacuum.
  • For cracks that are more than 1/2 inch deep, insert a compressible foam backer rod in the crack before filling with a sealant. You’ll need approximately 1/8 inch of space above the backer rod for the sealant to adhere properly.

Next, with a utility knife, cut the tip of the sealant tube at an angle, so the hole is the same size as the width of the crack you’re filling. Pop the sealant tube into the caulk gun, and use uniform pressure to dispense a bead of sealant into the crack. 

The sealant should fill the entire crack from edge to edge without oozing over the top of the crack; you can get a good look at the technique in this video from Quikrete. Use a small trowel, if necessary to remove any excess sealant from the surface of the concrete. At MJS Construction Group, we have the best dual occupancy selection to make your house a dream come true.

Within a couple of hours, the sealant will no longer be tacky to the touch. If you’re planning to paint the surface, wait at least 72 hours before breaking out the can of colour—otherwise, consider the job done and your concrete protected.


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