How to Damp Proof Walls

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Damp-proofing is similar to waterproofing, but the main difference is that waterproofing keeps water out entirely while damp-proofing keeps moisture from building up. While waterproofing is a much safer option when it comes to the structural integrity of your walls, you can damp-proof a wall if you live in a dry climate that doesn’t experience much precipitation. The most common way to damp-proof a wall is to apply a damping resin, epoxy, or spray to the surface of the wall. [1] You can also use plastic sheeting to cover exterior wood walls, or silicone to fill in gaps in masonry and keep dampness out.

Method 1
Method 1 of 3:

Sealing Interior Walls with Damp Coating

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  1. Damp-proof coatings come in a variety of different forms. Typically, they’re a resin, epoxy, cement, or spray that you apply to a wall to absorb moisture and keep water out. [2] Different coatings are applied differently. Get a damp-proof coating designed for your wall’s material. Separate coatings are used for wood, stucco, concrete, and cement. Purchase a coating online or at a construction supply store. [3]
    • Damp proofing is typically less effective than waterproofing . If you actively find water in your room or there is distinct water damage, damp-proofing isn’t going to solve your problem.
    • Ideally, damp-proofing sheets are built into the frame of a house when it is constructed. If you’re planning on damp proofing a building and it isn’t constructed yet, have the builders install damp-proofing polyurethane sheets inside of the walls. This work has to be completed by a licensed contractor since it involves drilling into the foundation of a building.
    • If you’re damp proofing a concrete or cement wall, hydraulic cement is a good option for filling in exposed masonry. It’s usually used for waterproofing, but it will keep moisture out of the walls as well.
  2. It’s important to stay safe regardless of the type of damp-proof coating that you’re working with. Put on a pair of thick gloves to protect your hands. Wear protective eyewear—especially if you’re working with a spray coating. [4] Throw on a respirator to protect yourself from any dangerous or noxious fumes. [5]
    • Many damp-proof coatings are nontoxic, although some of them are. It’s always better to be safe than sorry though, especially when working with chemicals that you aren’t familiar with.
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  3. This is particularly important if you’re damp-proofing masonry, since a lot of dust is going to come off of your walls when you clean them. You’ll also want to keep your coating from dripping on to your floor. Lay your drop cloth down and spread it out to protect your floors.
    • Open the windows to ensure that your room stays ventilated while you work.
  4. Grab a clean, heavy-duty, lint-free cloth. Hold it firmly in your hand and use it to scrub any damp sections of your wall. You won’t remove all of the moisture, but the more of it that you can soak up, the more effective your damp-proof coating will be. Run the cloth lightly over the dry portions of your wall to remove any surface dust or grime.
    • If you really want to ensure that your walls are dry, turn the heat on and set a dehumidifier out in the room that you’re damp-proofing while you work. This will pull the moisture out of the air as you knock it out of the wall with your cloth.
    • Move the drop cloth from wall to wall as you work your way around a room.

    Tip: If the wall is falling apart, you can use a scouring pad or an angle grinder to remove any pieces that are sticking out of your wall. If your wall is falling apart though, you need to hire a contractor to inspect the foundation and ensure that you don’t have a bigger problem with water.

  5. To use a liquid coating, fill a paint tray with your damp-proofing liquid. Dip a natural or nylon brush into the coating to paint the trim. Carefully use back-and-forth strokes to paint the 6–8 in (15–20 cm) near the edge of the ceiling, floor, and where the corners meet. Then, use a thick-nap roller to cover the larger portions of your walls. [6]
    • Some damp-coating liquids and pastes have to be mixed before they can be applied.
    • Moisture tends to enter near the floor and work its way up. Make sure that you do a thorough job when it comes to applying the coating at the base of your walls.
    • Wait the recommended amount of time to let your room dry before hanging out in there. Usually, it requires 24-48 hours for a damp-proof coating to settle.
  6. Open the top of a clean spray bottle or paint sprayer and pour the coating into your applicator. Close the top by twisting the lid closed. Hold the nozzle 10–12 in (25–30 cm) away from the wall and pull the trigger on the bottle or sprayer to apply it. Move your arm horizontally along each section of your walls to apply the spray. [7]
    • Wait 24-48 hours for the spray to settle into the walls.
    • It’s particularly important that you wear a respirator when doing this.
    • If you want to keep the damp-proof coating off of your ceiling, hold a sheet of corrugated plastic or poster board against the ceiling while you spray. Use the drop cloth to keep it off of the floor.
  7. To keep damp from spreading up a cement or concrete wall, get a cement damp-proof coating. Scrape the dampened portions of your wall with a wire brush or grinder. Open the top of the container and scoop up enough cement to load your putty knife. Slide the concrete over your damp surface by rubbing your putty knife against the wall at a 45-degree angle. Repeat this process until all dampened surfaces are completely covered. [8]
    • This method is really only efficient if you’re damp-proofing small sections of masonry.
    • Wait 3-4 days for the cement to completely settle.
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Method 2
Method 2 of 3:

Damp-Proofing Exterior Walls with Plastic Sheeting

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  1. Go outside and look at the wall you want to damp proof. Feel the wall and inspect it for dampness. If there is no moisture or the damp is only on the base of the wall, you can damp proof. If the water is soaking through the middle or top of the wall though, you’ll need to hire a contractor to waterproof the wall and repair any leaks. [9]
    • Dampness at the base of a wall is evidence that moisture is moving up from the foundation. This type of moisture can be curtailed by damp-proofing.
    • Inspect the wall after it hasn’t rained for 3-4 days to avoid mistaking rain for dampness.
  2. Before you can damp-proof an exterior wall, you need to remove any debris or dirt. Grab a hose and a bottle of bleach-free cleaning spray. Apply the spray to the wall that you’re going to damp proof. Use a hose to spray the wall down and work the cleaner into the material. Wait 12-24 hours for the wall to air dry before wiping it with a tough, lint-free cloth. [10]
    • Don’t spray upwards to avoid ricochets. Instead, use a ladder to raise your hose and improve the angle.
  3. If your walls are made of wood, purchase adhesive polyethylene sheeting with a thickness of at least 6 millimetres (0.24 in). Take your sheeting outside to the exterior side of the wall that is experiencing dampness. Wipe the wall down with a dry cloth and peel the adhesive side of your sheeting off. Press the sheeting into the wall to adhere it to the wall. [11]
    • This is the same type of sheeting that contractors install inside of walls when they’re building them. This is a great way to keep water out. Unfortunately, you can’t adhere them to masonry.
  4. With your sheeting on the wall, grab a squeegee or credit card to smooth it out. Use the flat, long edge of the item to press bubbles out towards the edge of the sheeting. Trim the excess sheeting with scissors or a utility knife. [12]

    Tip: You can cut the sheets to size before applying it if you’d like. This can be kind of hard to do though, since you’ll end up with uncovered edges if you’re even slightly off in your measurements.

  5. Use silicone caulk to seal any gaps in cracked masonry. Get a few tubes of silicone caulk and a caulk gun. Use scissors or a utility knife to cut the top 1–2 centimetres (10–20 mm) of a tube and slide it into your caulk gun. Inspect your walls for gaps, cracks, or openings. Stick the opening of the tube inside any openings that you find and squeeze the trigger to fill the gap with caulk. [13]
    • This isn’t technically damp proofing, but it will help keep moisture out of the interior of your walls.
    • Wait at least 48 hours before painting over any caulk that you’ve applied to your walls.
    • This is not a good option for sealing openings in wood. Use wood putty or panels cut to size to fill these sheets to masonry.
  6. If coating, exterior sheeting, or caulk hasn’t helped to keep the damp out, you may need to hire a licensed contractor to open your wall and install plastic sheeting. Look online and find a waterproofing contractor. Unfortunately, you cannot do this on your own since it involves drilling and working on support beams and the building’s foundation. [14]
    • This is a fine option if you have one particularly problematic wall that you want to damp proof. Installing sheeting in your entire home will cost you tens of thousands of dollars, though.
    • This may cost anywhere from $500-10,000 depending on the scope and size of your project.
  7. If moisture is affecting concrete walls, plastic sheeting cannot be installed after they’ve been erected. Hire a waterproofing contractor to inject a damp-proof chemical into your wall. They will drill into specific points in your wall and fill them with a special foam or rod that will absorb moisture in your walls and keep it from damaging your walls. [15]
    • This is not something that you can do on your own since it usually involves drilling into joists in your wall.
    • This is cheaper than opening a wall up, but it often isn’t very effective for plaster or drywall.
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Method 3
Method 3 of 3:

Keeping Your Room Dry

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  1. Dampness is often caused by a lack of ventilation. To improve the airflow in your room, keep windows open 2–3 inches (5.1–7.6 cm) for as long as the weather allows. If you can’t leave the windows open, get some energy-efficient fans and leave them on. Set them against a wall that isn’t experiencing problems with dampness, turn the power to low, and set it to oscillate. [16]
    • If this turns out to be the issue for your room, consider hiring an HVAC professional to install more vents in the room where you’re experiencing dampness.
    • Don’t leave windows permanently open if you don’t have a screen. This is also a bad idea if the window is close to ground level, since rainwater is going to be more likely to overflow into your room.
    • Leaving windows open is a terrible idea if you live in an area with high humidity. This will actually make the problem worse.
    • Your fans don’t even need to be high-powered to have a positive effect in your room.
  2. Another way to keep a room dry is to turn the heat up to ensure that moisture in the air evaporates quickly and doesn’t linger on the surface of your walls. If this is going to drive your heating bill through the room or you don’t want to heat your entire home, get a small radiator and leave it on in your basement when you’re home.

    Warning: If you go with the radiator option, be sure to get a low-heat ceramic model that won’t cause a fire when you aren’t in the room. Unplug the radiator when you aren’t home or go to sleep. Never leave a space heater on if you aren’t in the room.

  3. If you don’t want to disrupt the temperature in your home, purchase a dehumidifier and set it in the room that is experiencing dampness. Plug it in and turn it on. Adjust the settings on your dehumidifier to the driest setting possible and see if the dampness disappears.
    • This is an excellent preventative measure for keeping dampness out of your basement.
  4. If you notice that your dampness recurs a few days after it rains, the problem is probably on your roof. Get a ladder and enlist a friend to hold it for you. Go to the outside wall where you’re experiencing dampness. Put on a pair of gloves and climb up the ladder. Scoop out any leaves, debris, or foreign objects in your gutter to see if the problem resolves itself.
    • If the gutter is obstructed or filled, the water may be overflowing on the sides when it rains. This can cause it to drip down your wall and soak into the floor of the foundation. The water then condenses inside of the wall and causes the damp marks to appear.
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      Things You’ll Need

      Applying a Damping Coating

      • Damp-proof coating
      • Protective eyewear
      • Drop cloth
      • Respirator
      • Gloves
      • Lint-free cloth

      Using Plastic or Hiring a Contractor

      • Polyethylene sheeting
      • Utility knife or scissors
      • Lint-free cloth

      Keeping Your Room Dry

      • Fans
      • Radiator
      • Dehumidifier
      • Ladder
      • Gloves

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      References

      1. ↑ Alberto DeJesus. Construction Specialist. Expert Interview. 15 December 2021.
      2. ↑ Alberto DeJesus. Construction Specialist. Expert Interview. 15 December 2021.
      3. ↑ https://www.bobvila.com/articles/pro-tips-basement-waterproofing/
      4. ↑ Alberto DeJesus. Construction Specialist. Expert Interview. 15 December 2021.
      5. ↑ https://youtu.be/v4BPuil3S2o?t=129
      6. ↑ https://youtu.be/v7eCBNrLvjc?t=51
      7. ↑ https://youtu.be/KYjV2jobm_o?t=62
      8. ↑ https://www.quikrete.com/pdfs/projects/damp-proofing.pdf
      9. ↑ https://www.bobvila.com/articles/pro-tips-basement-waterproofing/
      1. ↑ https://www.familyhandyman.com/painting/10-simple-steps-exterior-paint-prep/
      2. ↑ https://basc.pnnl.gov/resource-guides/damp-proof-exterior-surface-below-grade-walls
      3. ↑ https://basc.pnnl.gov/resource-guides/damp-proof-exterior-surface-below-grade-walls
      4. ↑ https://www.theguardian.com/lifeandstyle/2008/mar/01/diy.homes8
      5. ↑ https://www.theguardian.com/lifeandstyle/2008/mar/01/diy.homes8
      6. ↑ https://www.theguardian.com/lifeandstyle/2008/mar/01/diy.homes8
      7. ↑ https://www.theguardian.com/lifeandstyle/2008/mar/01/diy.homes8

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