Proper Installation of Vertical Expansion Joints for Homes and Commercial Buildings
Most homeowners are familiar with the vertical expansion joints on the back and sides of their homes—those straight seams where two walls or sections of brick, stucco, siding, or concrete meet. On commercial buildings, you’ll see them even more often: long vertical separations designed to handle movement across large wall spans.
These joints aren’t cosmetic. They’re intentional “movement zones” that let the structure expand, contract, and shift slightly without cracking. But when the sealant in those joints erodes, shrinks, or pulls away, it stops doing its job—and that’s when water, pests, and expensive interior damage can start.
At Sealtechs, we seal vertical expansion joints to stop intrusions, protect the building envelope, and prevent the common chain reaction that leads to interior moisture issues.
What Vertical Expansion Joints Do
Vertical expansion joints (also called control/movement joints in many wall systems) are designed to:
- Absorb building movement from temperature swings and settling
- Prevent cracking in brick, stucco, EIFS, fiber cement, and concrete wall sections
- Provide a sealed transition between different materials or wall planes
But the key is this: the joint only works if it’s sealed correctly.
What Happens When Vertical Joint Sealant Fails
Over time, exterior sealant is exposed to brutal conditions: UV rays, heat cycles, rain, wind-driven water, and general aging. When it erodes or separates from the wall, problems show up fast:
1) Moisture intrusion → moldy drywall inside
A failed vertical joint can funnel water into the wall assembly. That moisture doesn’t always show on the outside. It can travel behind finishes and show up inside as:
- Soft or stained drywall
- Musty odors
- Mold/mildew growth
- Peeling paint or bubbling texture
This is one of the most common reasons homeowners discover “mysterious” interior wall damage—especially after heavy rain.
2) Pest invasions
Small gaps become easy access points. Once sealant pulls away, the joint can become an entry route for:
- Ants
- Roaches
- Wasps
- Spiders
- Rodents (in larger separations)
If a pest can fit through it, it will.
3) Material deterioration
Water entering behind cladding can cause swelling, rot, corrosion, or freeze-thaw damage (in colder climates). Even in warm regions, constant moisture accelerates wear and leads to larger repairs.
Proper Vertical Expansion Joint Installation
A vertical joint is not a place for “quick caulk.” Proper installation follows a system designed for adhesion, flexibility, and long-term performance.
1) Remove failed sealant and contaminants
We begin by removing:
- Old cracked or peeling sealant
- Loose debris, dirt, and chalking
- Any material preventing a clean bond
If old sealant is left behind, new sealant is only as good as the weak layer it’s stuck to.
2) Prepare and clean the joint walls
For long-term performance, the joint edges must be clean and stable. This may include:
- Mechanical cleaning (as needed)
- Dust removal and proper dry-out
- Ensuring the sides of the joint are sound and ready to bond
Adhesion is everything on vertical joints—especially where wind-driven rain is common.
3) Install backer rod to control depth and shape
A backer rod is placed to set the correct depth and keep the sealant working properly.
Backer rod helps:
- Prevent overfilling (wasting product)
- Create the correct joint profile
- Improve movement capability
- Reduce stress that causes sealant to tear
This is one of the most important steps and one of the most skipped by amateurs.
4) Apply polyurethane sealant (tooling for a tight seal)
We apply a high-performance polyurethane sealant designed for exterior movement joints. Then we tool it to ensure:
- Full contact to both sides of the joint
- No voids or bubbles
- A smooth finish that sheds water
A properly tooled sealant bead isn’t just prettier—it seals better and lasts longer.
5) Cure and final inspection
Sealant must cure before it reaches full performance. Once cured, the joint should remain flexible while maintaining a tight seal against water intrusion.
Why Sealtechs Seals Vertical Joints
Our goal is simple: stop the intrusions. When vertical joints are sealed correctly, you gain real protection:
- Blocks water intrusion that can lead to interior drywall damage and mold
- Reduces pest entry points
- Helps prevent cracking and material separation around the joint
- Improves curb appeal by restoring clean, finished seams
- Extends the life of exterior finishes by keeping the wall system drier
Signs Your Vertical Joints Need Resealing
If you notice any of these, it’s time:
- Sealant is cracked, missing, brittle, or peeling away
- Gaps you can visibly see into
- Interior drywall stains near exterior walls
- Musty smell after rain
- Increased insects along certain walls or corners
The Bottom Line
Vertical expansion joints are one of the most overlooked—but most important—seals on a home or commercial building. When they fail, they can let water into the wall system, leading to moldy drywall, hidden damage, and pest invasions.
Sealtechs seals vertical joints the right way—clean removal, proper prep, backer rod depth control, and high-quality polyurethane sealant—so your building stays protected, dry, and sealed tight.