Yes, you can fix a concrete roof from leaking by finding the leak source, cleaning the area, filling cracks with cement or sealant, and applying a waterproof coating to protect the whole roof. This guide will show you each step in simple terms so you can stop those annoying drips and protect your home.
Water dripping from your ceiling is never fun. It can damage your walls, grow mold, and make your home feel unsafe. But fixing a concrete roof leak doesn’t have to be scary or hard. With the right steps and some basic tools, you can get your roof back in good shape.
Why Does a Concrete Roof Leak?
Before you start fixing anything, you need to know what causes these leaks in the first place.
Cracks and Holes in the Roof:
Concrete becomes prone to cracks and holes due to everyday wear and tear. The sun, rain, wind, and changes in temperature all make concrete expand and shrink. Over time, this creates small cracks. Even tiny cracks can let water sneak through and drip into your home.
Poor Drainage and Standing Water:
When water sits on your roof instead of flowing off, it finds weak spots and seeps through. If the slope is too shallow or flat, water can pool on the roof’s surface, leading to leaks and water damage. This is especially bad during heavy rainstorms.
Old or Damaged Waterproofing:
Concrete itself is not waterproof—it’s more like a sponge. That’s why roofs need special waterproof coatings. When these coatings get old or crack, water gets through the pores in the concrete.
Damaged Flashing:
Flashing is a thin material, typically made of metal, that protects the joints and angles of a roof. It goes around chimneys, vents, and roof edges. If flashing gets bent, rusted, or comes loose, water can get behind it and leak into your home.
Broken or Loose Tiles:
For tile roofs made from concrete, broken or loose tiles let water get to the layers underneath. Sometimes the problem isn’t the tiles themselves but the felt or membrane below them that has worn out.
How to Find Where Your Roof Is Leaking
You can’t fix a leak if you don’t know where it is. Here’s how to track it down.
Look for Water Stains Inside:
Check your ceiling for brown or yellow stains. These spots show where water is coming through. But here’s the tricky part—concrete is permeable, which means water drainage or collection at one point can result in a leak at another point. The leak on your ceiling might not be directly below the problem on your roof.
Check the Roof Surface:
On a dry day, go up and look at your roof carefully. Look for:
- Visible cracks or holes
- Puddles of standing water
- Loose or broken tiles
- Damaged areas around vents and chimneys
- Signs of mold or moss
Do a Water Test:
If you can’t find the leak by looking, spray water from a garden hose on different parts of your roof. Have someone inside watch for drips. Start at the lowest part of the roof and work your way up. This helps you find the exact spot where water is getting in.
Check Plumbing and Drainage:
Sometimes the leak isn’t from rainwater at all. Check any plumbing pipes or drainage systems on your roof. A leaky pipe can cause just as much trouble as a cracked roof.
What You Need to Fix Your Concrete Roof
Before you start working, gather these basic supplies:
- Pressure washer or stiff broom
- Wire brush or scraper
- Concrete roof sealant for leaks (mortar or roof cement)
- Roof primer
- Elastomeric sealant or waterproof coating
- Paintbrush or roller
- Safety gear (gloves, goggles, non-slip shoes)
- Ladder (if needed)
Step-by-Step Guide to Fix a Concrete Roof Leak
Now let’s get to work fixing that leak.
Step 1: Clean the Roof Surface
Before you proceed, make sure to clean the entire roof surface using a pressure washer to remove all kinds of debris and dirt, like dust, mud, twigs, and leaves. A clean surface helps sealants stick properly. Take your time with this step—it makes a big difference.
Step 2: Fill Cracks and Holes
Once the roof is clean and dry, it’s time to fill those gaps.
For small cracks (less than a quarter inch):
- Use a wire brush to clear out any loose pieces
- Apply silicone caulk or elastomeric sealant
- Smooth it out with a putty knife
For larger cracks and holes:
- Use cement compound sealant to seal the crack width if it’s more than 5mm
- Fill the area with mortar or roofing cement
- Let it dry completely before moving on
Step 3: Apply Roof Primer
After filling the cracks, apply a layer of roof primer. AMES Super Primer will dry rapidly and flow into the cracks and crevices of the concrete rooftop, bonding to the concrete with remarkable adhesion. This creates a smooth base and helps the waterproof coating stick better. Let it dry for 30 minutes to an hour, or follow the product instructions.
Step 4: Add Waterproof Sealant
This is the most important step. Apply an elastomeric sealant or waterproof coating over the repaired areas and then the entire roof surface. These products stretch and move with your roof as temperature changes, preventing new cracks from forming.
Apply two coats:
- First coat: Cover all repaired spots, corners, and edges
- Let it dry for 24 hours
- Second coat: Apply over the entire roof for full protection
For concrete flat roof leak repair, apply two coats of a water-repellent sealer within 2 to 4 hours of each other to make the concrete surface water-repellent after a 24-hour cure time.
Step 5: Check Flashing and Seams
Don’t forget about the flashing around vents, chimneys, and roof edges. Make sure these metal strips are flat and sealed tightly. Use roofing cement to secure any loose sections.
Special Tips for Different Types of Concrete Roofs
Flat Concrete Roof Leaking:
Flat roofs are more likely to have standing water. Make sure your roof has a slight slope toward drains. Even a small tilt helps water flow off instead of sitting in puddles. Consider installing better drainage if water pools regularly.
Concrete Tile Roof Leaking:
If you have concrete tiles, check for:
- Cracked or broken tiles that need replacing
- Gaps between tiles where water can sneak in
- Old roofing felt underneath that might need replacing
Sometimes you can slide out a broken tile and replace it with a new one without much trouble.
Concrete Roof Leaks in Heavy Rain:
If your roof only leaks during big storms, the problem might be overwhelmed drainage or gaps in your waterproofing that only show up under heavy water flow. Focus on improving drainage and making sure your waterproof coating is thick and complete.
When to Call a Professional?
Some jobs are best left to the experts. Always hire a professional roofer to pull permits, inspect, and fix roof damage, especially if:
- The leak is large or in multiple spots
- You see structural damage or sagging
- More than 25% of your roof needs repair
- You’re not comfortable working at heights
- The roof is old and might need full replacement
- You have extensive water damage inside your home
Professional residential construction experts have the right tools, training, and safety equipment to handle complex repairs safely.
Best Solutions for Leaking Concrete Roof
The best solution depends on your specific problem:
For minor leaks: Clean, fill cracks, and apply elastomeric sealant.
For flat roofs: Ensure proper slope and apply multiple coats of waterproof membrane.
For tile roofs: Replace broken tiles and check the underlayment.
For old roofs: Consider a professional waterproofing system or coating
How to Prevent Future Leaks
Once you’ve fixed your leak, keep it from coming back:
Regular Inspections:
Have a qualified roofer inspect your roof at least once a year, preferably before the monsoon, to assess for damage such as cracks in the roof and loose flashing. Catching small problems early saves money later.
Keep Drains Clear:
Debris like leaves, branches, and dirt can trap water and cause water leakage from roofs. Clean your gutters and roof drains regularly, especially before rainy seasons.
Reapply Sealant When Needed:
Waterproof coatings don’t last forever. Depending on your climate and the product used, you may need to reapply protective coatings every 5 to 10 years. Watch for signs of wear like peeling or cracking.
Fix Small Problems Fast:
Don’t ignore a tiny leak thinking it’s no big deal. Small leaks grow into big, expensive problems. Fix them as soon as you notice them.
Consider Professional Waterproofing:
For long-term protection, consider having professionals apply a high-quality waterproofing system. A professionally applied waterproofing system can last 8 to 12 years.
Common Mistakes to Avoid
Don’t fall into these traps:
Fixing only the spot above the leak: Water travels through concrete, so that the actual problem might be somewhere else on the roof. Always inspect the whole surface.
Skipping the cleaning step: Sealants won’t stick to dirty or wet surfaces. Clean thoroughly and let everything dry completely.
Using the wrong products: Not all sealants work on concrete. Make sure you’re using products designed for concrete roofs.
Ignoring safety: Working on roofs is dangerous. Use proper safety gear, work on dry days, and never work alone. If you’re not confident, hire a pro.
Waterproofing only the leak spot: The best option is to waterproof the entire roof, regardless of where the leaks are found. This prevents future problems.
Final Thoughts
Fixing a concrete roof from leaking isn’t as hard as it sounds. With some basic tools, the right materials, and these simple steps, you can stop those drips and protect your home from water damage. Remember to find the source of the leak, clean well, fill all cracks, and apply a good waterproof coating over the whole roof.
If the job feels too big or you’re not comfortable doing it yourself, that’s okay. Professional roofers have the experience and equipment to get the job done safely and correctly. At UDA Services, we understand that your home deserves quality care and expert craftsmanship.
Whether you choose to DIY or hire help, the important thing is to act fast when you spot a leak. The sooner you fix it, the less damage water can do to your home. Don’t wait—take action today and enjoy a dry, safe home again.
Need help with your roof or other home additions? Reach out to experienced professionals who can guide you through the process and deliver lasting results.