Buzz
Eliminate rising damp once and for all with this reliable DIY method. Rising damp occurs when water penetrates through a brick foundation, causing damage to your walls. This issue is commonly found in older homes lacking a damp proof course (DPC) or where the DPC has failed. Fortunately, you can easily address rising damp using a chemical cream treatment. Once applied, the cream waterproofs the bricks, preventing further rising damp issues.
Steps to Follow
Clearing and Drilling the Wall
Break through the wall render internally using a hammer and chisel. Identify discolored and moist areas on your wall. Wear sturdy gloves and remove any loose sections by hand. Position the chisel blade against the wall approximately 3–4 inches (7.6–10.2 cm) above the highest point of the rising damp. Use the hammer to strike the chisel's end and break apart the wall render. Remove all affected areas down to the floor level.
- The render refers to the plaster or cement-like material covering the brick wall.
- For cutting through plaster wall finishes, employ an angle grinder for efficient cutting.
- If rising damp affects only a portion of the wall, it's unnecessary to remove render from the entire room.
Drill holes every 2½ in (6.4 cm) along the lowest mortar line. Utilize a hammer drill with a ½ in (1.3 cm) masonry bit. Position the drill between the first and second layer of bricks above the floor, also called the mortar line. Activate your hammer drill and exert steady pressure to create holes in the mortar. Continue drilling holes across the affected area, spacing them 2½ in (6.4 cm) apart or having 3 holes per brick. Ensure each hole penetrates at least ¾ through the bricks.
- If you lack a hammer drill, consider renting one from nearby hardware stores.
- Wear a facemask and safety glasses to protect against dust when drilling through brick.
Pro Tip: For walls on the edge of your home, drilling into the bricks from outside is an option.
Vacuum the holes to remove any dust. Use the hose attachment of your vacuum and hold it against each hole to clear out dust. Ensure thorough cleaning to optimize adhesion of the DPC.
Applying a Chemical DPC
Inject DPC cream into the holes using a caulk gun. Load the DPC cream tube into the caulk gun and cut the nozzle tip. Insert the nozzle deeply into each hole and squeeze the caulk gun trigger. Allow the cream to fill the hole, gradually withdrawing the nozzle. Repeat for each hole in your bricks.
- The quantity of DPC cream required depends on wall length and thickness. Plan for 1 US gal (3.8 L) of DPC cream per 30 ft (9.1 m) of coverage for a 9 in (23 cm) thick wall.
- Find DPC cream at hardware stores or online.
Pro Tip:
If you lack a caulk gun, consider using a pressure pump pack, similar to a garden sprayer.
Alternatively, you can purchase DPC fibre rods from hardware stores or online. These rods eliminate the need to calculate the correct amount of DPC cream and prevent overspill.
Allow the cream to set overnight. With time, the cream will transform into a liquid and permeate the surrounding bricks, rendering them waterproof. Leave the cream undisturbed for a minimum of 12 hours to ensure proper setting.
Apply another layer of cream treatment the next day and allow it to set. Once the initial cream application has set, reinsert the caulk gun nozzle into each hole and administer another coating of cream. Let the cream set for another 12 hours to allow absorption into the brick pores.
- Depending on the affected area's size, you may require an additional package of DPC cream.
Wall Repair
Prepare a waterproof mortar in a 5 US gal (19 L) bucket. Opt for a 30 lb (14 kg) bag of pre-mixed waterproof mortar from your nearby home improvement or hardware store. Empty the mortar bag into the bucket and add 2 US qt (1.9 L) of water. Thoroughly mix the contents with a trowel until achieving a toothpaste-like consistency.
Pro Tip: Should you overwater your mortar, allow it to sit for 5-10 minutes to slightly solidify.
Apply the mortar into the holes using a trowel. Utilize a flat trowel to extract the mortar from the bucket and press it into the hole as deeply as possible. Smoothly scrape off excess mortar until it aligns with the surrounding bricks. Proceed to fill all holes with the mortar.
- If the mortar begins to harden while working, add a small amount of water to the bucket and remix.
- Complete filling the hole is unnecessary since the surrounding bricks are waterproof.
Allow the mortar to dry for 48 hours. Permit the mortar within the holes to set completely, typically requiring 2 days. During this period, refrain from disturbing the mortar to ensure even drying inside the hole.
- If fast-setting mortar was utilized, it might dry entirely within 1 day.
Wait 2-4 months before applying a new render. Given the wall's prior dampness, it necessitates time to dry thoroughly. Allow the wall to air dry completely to prevent moisture entrapment behind the new render.
Pro Tips
Important Warnings
- Avoid painting directly over the damp area as it indicates an underlying issue.
- Always prioritize wearing safety glasses when using power tools.
Essential Tools
- Protective work gloves
- Hammer
- Chisel
- Safety glasses
- Face mask
- Hammer drill
- Vacuum
- DPC cream
- Caulk gun
- Waterproof mortar
- Flat trowel
