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Control Joints – How to Clean and Fill

Process of how to fill control joints correctly.

Step 1: Clean out the control joints and vacuum. Run a joint saw through the existing control joint to expose a fresh wall of the joint slightly. Example: If your joint is a 1/4 inch thick, you should run a 1/4 joint cleanout blade or a 5/16 blade after running your joint saw through the existing joint vacuum all remaining dust out of control joint.

Step 2: Fill the control joint with a two-pass system. Make sure to do a quick pass and then come back with a slow pass to overfill the control joint. You must overfill with a two-part polyurea in order for the joint to be shaved flush. Do not use backer rod since full depth is needed. Only use backer rod if filling a cold joint.

Step 3: Allow the material to dry for about 30-60 minutes and shave it flush with a razor scraper. If large enough joint, you can scrape with a ride-on scraper.

Step 4: Clean out your joint pump. Either you have to get it ready for the next day or do a full cleanout if your pump will sit more than 72 hours.


Success factors on filling control joints

  1. Material has to be at least 78F before you shoot the material. If not, your pump may go off ration. The ISO side doubles in thickness every 10F; it drops.
  2. Allow the material to sit for a minimum of 30 minutes before shaving.
  3. Have your razor scraper down low when you go to shave the control joints.
  4. If using hand tubes, make sure you pump 2-3 times into a bucket before pumping into the control joint. The material has to get mixed in the static mixer tube correctly before filling the control joint.
  5. Make sure your joint pump is cleaned and working properly.


Equipment List Needed:

  • Joint Saw
  • Joint blade
  • HEPA Vacuum
  • Hand tubes- (If doing by hand)
  • Joint Pump- Better and more cost-effective if doing more than a 300 linear ft of joints.
  • Razor Scraper


Material List:

  1. Hand Tubes-If doing by hand
  2. 10-gallon kits if doing with a joint pump
  3. Static Mixers
  4. Razor Scraper with sharp razor blades.

For ordering or any other questions, please give us a call.