Caulking: The Basics

by | Apr 2, 2023 | Ask the Expert, Knowledge Base

Here are the basics to get anyone started installing caulking or for anyone to be able to confidently hire a contractor and inspect their work on a property.

Do you want to avoid installing a less than satisfying looking caulking bead? Do you want to make sure that the contractor you hired is doing the work properly but you have no clue what you’re looking at? A quick google search, or scouring through youtube for videos will leave you with more questions than answers. Here at ArmourCo, we stand by our Engineer approved, high standard of caulking installation. If you’re looking for the best, most comprehensive guide to redoing caulking, hold on tight and we won’t let you down.

Filling the gap

There are supposed to be gaps around your windows and doors! These gaps are meant to be there so that insulation like spray foam can be installed, preventing drafts and condensation. But what do we do when we find them on a sealant project? Some contractors will just pump and pump more material inside, that’s the easiest thing to do. Most times, the easiest thing to do is also the wrong thing. This is one of those times. What you need to do is get the right material and fill the gap to prevent three-way adhesion and a complete waste of material.

Pick the right material

a) Spray foam

    1. Purchase low-expansion spray foam, this spray foam only expands 10% beyond what you spray and will not damage the frame of your window or door
    2. Spray the foam in a consistent motion, allowing the spray foam to be about ¼” to ½”, depending on the gap size
    3. Let the spray foam dry, it should only slightly protrude the door/window frame. Take a sharp knife, and cut the spray foam flush to the frame, remove all residue.

b) Backer Rod

      1. This product can be found at some hardware stores, but specialty construction stores will have varieties.
      2. The diameter of the backer rod must be 25% bigger than the gap you are trying to fill. This is for proper compression in the gap for condensation prevention.
      3. Always cut the backer rod to length prior to installing, do not install it off the roll, to prevent twisting.
      4. Install backer rod using a flat tool such as a 5 in 1, or equivalent. Push backer rod in from the bottom or the top, not the middle. When backer rod is installed correctly, it will keep the look of the rod prior to installation. If there are wrinkles or it looks braided, this is incorrect.
      5. Backer rod will be installed flush or slightly protruding the gap. Take your flat tool across the window frame and push it across the gap to see if it is done correctly.
Three sided adhesion. What’s that?

When two substrates move, the sealant expands and contracts to bridge those two materials. If the caulking is in contact with a third surface, it cannot properly move and will result in failure, showing itself by cracking or splitting either in the middle (a cohesive failure) or along the substrate (an adhesive failure).

Cleaning the substrate

Nothing sticks to dirt. It’s a very simple idea, but incredibly critical to the longevity of the caulking that gets overlooked far too often. Every substrate, from bricks to metal flashing, needs a specific type of prep for the caulking to adhere to it. But how do we know when what we are cleaning is good enough? That’s where doing, or seeing your contractor complete a two-stage wipe technique will give you the confidence that your caulking will last.

  1. Brush off all dirt and residue with a clean brush.
  2. Use 90-100% isopropyl alcohol, apply to clean rag. Wipe substrate to saturate and clean.
  3. Take a second clean rag, and wipe same area again.
  4. Allow alcohol to evaporate.
  5. If there is dust from brick or concrete after wiping, brush off again.

We’re ready to caulk! The surface is prepped, three-way adhesion avoided, now the art of caulking is needed. We have all either seen someone caulk confidently, or even tried ourselves. Like everything else, there are rules. Rule number one, no fingers allowed! Rule number two, you must have proper adhesion! We should explain these rules.

  1. Size of the bead
    1. When cutting the tip of the caulking, we must ensure the size is correct.
    2. Caulking beads MUST be at least ¼” thick, and 3/8” on both substrates.
    3. Make sure the nozzle is slightly past 90 degrees.
  2. Laying the caulking bead
    1. Uniformly pump out the caulking in a continuous, smooth manner.
    2. The caulking bead should be installed on a 45-degree angle and sealed along the edges
    3. For a caulking bead to expand and contract, the bead must be slightly concave, if a convex bead is found, the caulking will most likely have an adhesion failure in the future.
    4. After laying the caulking bead, you must seal the edges using wood sticks that are specially made by the contractor (shown here) or metal tooling sticks that can be purchased at specialty stores.

So, there we go, caulking. We always say, it’s not hard to do, but it’s hard to do properly. There are many contractors that will say they do caulking but will preform sub par. These simple steps, that are approved by all Structural Engineers and to our high standard, is a great reference to ensure no matter who you hire, the job will be done properly.