You will probably find cinder block walls not just in your basement but in the basement or foundation of many other homes around the neighborhood as well. They are cheaper than other options and easy to work with during construction because they are lightweight. But cinder block walls can be problematic, particularly in older homes and damp weather like we get in Ottawa and surrounding areas throughout the seasons.

Cinder block foundation walls are less robust than other options, such as poured concrete or a standard concrete block. This is because they have a much higher porosity which makes them permeable to water. Cinder block walls also have more weak points within. That’s why you should address cracks and any other signs of damage you notice in your basement walls as early as possible. 

You can fix some damage yourself, such as small cracks and holes in your cinder block walls. But if your basement has dampness, a foul odor, bowed walls, mold growing extensively, or pest infestation, then the cracks are symptoms of a greater problem. You should seek professional help instead of trying to fix them yourself.

To help understand how much work goes into patching a cinder block wall, we’ve laid out the steps for you below, along with some of our hard earned tips and tricks for avoiding mistakes:

Step 1 – Gather the Tools and Materials You Will Need

If you think that the damage is small enough to fix by yourself, here are some tools you will need to patch cinder block walls in your basement: 

  • Metal file 
  • Chisel
  • Stiff brush
  • Hammer
  • Shop vacuum (optional)
  • Mortar mix or Portland cement and sand
  • Water
  • Bucket for mixing
  • Trowel
  • Spray bottle
  • Cement epoxy (optional)
  • Board (optional)
  • Rubber gloves
  • Respirator mask
  • Safety goggles

Step 2 – Protect Yourself

Don gloves, goggles, and a respirator mask. You should also wear overalls or long pants when you do the repair work. Inhaling cement dust and fine particles can irritate your respiratory system. 

Cement has a high pH, and it can also cause itching and discomfort when it comes in contact with your eyes and skin. Some people can experience more serious problems, such as caustic injury and cement burns. 

Step 3 – Clean the Damaged Area

You will need to clean debris, cement, and mortar from cracks and holes before you patch them. This will make sure that the mortar or cement you use will adhere properly. 

Use a chisel to scrape out the debris from the crack or hole. Dislodge any loose and crumbling pieces of cinder. Use a stiff brush to clean the debris from the holes and cracks. You can also use a shop vacuum to remove smaller particles inside. 

File the rough edges around the cracks and holes with a metal file until they are smooth. Smooth edges will make the process easier and help ensure that the repair lasts for a long time. 

Step 4 – Prepare the Filler

A mortar mix is ideal for the job, particularly for holes and wider cracks. But if you don’t have it, you can make your own filler with cement and sand. To make the filler, mix one part of Portland cement with three parts of sand. You can use a smaller bucket to measure the quantity. Use a trowel to remove excess cement or sand from the top of the bucket to keep it level when you measure. 

Pour the filler into a large bucket. And then carefully add a small amount of water. The texture of your filler should be thick. You should be able to use it like putty, and you need it to retain its form when you shape it. 

If the mixture is too runny, you cannot fill in the gaps properly. Especially because the cracks and holes you’re dealing with are vertical because they’re on walls. A runny mixture will not stay put inside the gaps. 

Step 5 – Patch the Cracks

To patch the cracks, you need to take a slightly different approach than patching holes. You can use this method on cracks that are wider than ⅛ inches. 

After you have cleaned the crack, use a spray bottle to lightly mist the opening. Don’t overdo it, you don’t want it to be wet, but lightly misting the crack will help the filler in adhering. 

Use a trowel to pack as much filler or mortar as you can inside the crack. Make sure you’re using enough mortar to fill the crack deeply. After that, scrape the mortar over the crack and spread it evenly on the wall. 

Step 6 – Patch the Holes

To patch holes, you need the mortar to be slightly less runny in texture than patching cracks. Roll the mortar mixture in your hands to form a cone shape. You need to be quick to prevent the mortar from hardening before you patch the hole. 

Make the wide end of the cone wider than the hole you’re patching. Fit the narrow end of the cone inside the hole and get as much mortar inside it as you can. When the hole is filled completely, scrape the mortar over it with a trowel and spread it evenly. 

Useful Tips for Patching Your Cinder Block Basement Walls

  • For better results, use cement epoxy to patch the holes along with mortar. Line the inner edges of the hole or crack with cement epoxy before you fill them in with the mortar. The repair will be sturdier and last longer. 
  • You can also hold up a board against the hole you’ve just patched with cement epoxy and mortar for about five minutes to let the epoxy and mortar bond and dry. 
  • Avoid the repair work in rainy or humid weather
  • Try to finish the process within 20 to 30 minutes after you prepare the filler