Exterior Caulking Maintenance

Keep the Water Out

When siding moves, caulk breaks open, that allows water to flow in and rots the sheathing. This can be a slow degeneration, that may go unnoticed which discovered can be substantially more expensive than regular caulk maintenance. Structural damage and mold will ultimately result from lack of caulking maintenance.

Typically, when a home is repainted, a painter will inspect and fill any voids in the caulk prior to painting. Every year your home is not painted you need to inspect the caulking for gaps, separation from solid services, and crumbling.

What Gets Caulk

Caulking compounds (sealants) are available in a variety of formulations and colors, and for an assortment of intended uses, like cement and woods. Caulking may be:

  • Inserted into gaps, cracks and holes in any construction material
  • Used over a junction of adjoining sections of metal, wood, cement plaster, masonry or other two dissimilar building materials

It is very important to note that different types of caulk are used in different locations and that some knowledge is required when selecting the correct caulking product.

Be aware that some types of sealants are not designed for exterior exposure. If caulking compounds of an improper type are applied where they are exposed to sunlight, heat and weather, relatively early failure of the applied sealant should be anticipated. If interior-type sealants are inadvertently applied to exterior exposure, they should be removed as soon as the first indication of deterioration becomes evident.

An incomplete list of possible locations which might receive caulking:

  • Junctures of vent stacks with a roof
  • Junctures of chimneys with a roof
  • At anchors for TV aerials, where the anchors pierce the roof membrane
  • Over fasteners which have been incorrectly driven vertically downward through wood or metal caps of parapet walls, balcony walls, wing walls or other construction features
  • Where the low fence of a "widow's walk" rests upon a roof
  • At junctures of adjacent sections of sheet metal coping installed on top of a parapet wall
  • At perimeters of penetrations through exterior walls. Examples of some penetrations are: windows & doors or electrical, plumbing, HVAC

How to Identify Failing Caulk

Deterioration or failure of exterior or interior grade caulking may become evident as:

  • shrinkage of the bead of sealant
  • delamination (caulk no longer sticks to surface)
  • cracking of the bead
  • powdering or dusting of the surface of the caulking.

Areas to Check

Examine the following parts of your house to see if caulking may be needed:

  • Where the siding meets the foundation
  • Around air ducts or vents, heating or cooling equipment, openings for plumbing or wiring
  • Where window or door frames meet siding
  • Around skylights and the chimney
  • Where different types of building materials meet
  • Where wood, vinyl or aluminum siding forms corner joints

Properties of Good Quality Caulk

All caulking material must have excellent adhesion properties so that it can be used with a variety of building materials, even under wet conditions. To maintain a watertight and airtight seal, it must also be flexible. It's also important that a caulk be able to maintain these properties over time or it can pull away from the surface and fail to do its job. A good quality caulking material must also be attractive and stay clean, even after years of service.

Just to reiterate, different caulks have different stretching capabilities. Check caulk elasticity measurement specification sheets to make sure you are using the correct product.

Choosing the Right Exterior Caulk

If you prepare your home for winter by sealing out moisture and outside air with a high performance caulk, you'll not only reduce energy costs you'll prevent costly repairs from rotted wood and blistering paint. Proper caulking also will retard the growth of mold and mildew and it will reduce the number of insects and small creatures who visit your home looking for food, shelter and warmth.

There are lots of good reasons to check the caulking around your home and make sure it's in good condition. If you find that recaulking is needed, how do you find choose the right one when there are so many types of caulk to choose from?

When you're choosing an exterior caulk, ask yourself these questions:

  • What surface(s) will it be applied to? Is a specialty caulk the best choice? For instance, choose a specialty caulk use on brick.
  • Do the caulked surfaces need to be painted? If so, don't use a 100% silicone caulk because it's not paintable.
  • If the adjacent area can't be painted at all (such as where vents or flashing meet the roof), what color caulk would work best, or should you use a clear caulk?
  • How large are the gaps or cracks that need to be bridged? Most caulks work best on cracks that are less than a quarter of an inch wide. If you do need to caulk a wider gap, choose a specialty caulk formulated for this purpose or first fill part of the recessed area with backer rod.
  • Do you prefer a caulk that's user-friendly? Some caulks require mineral spirits be used for clean up, and some caulks such as high quality urethanes are very difficult to apply. If you require ease of use and water clean up, choose a siliconized latex caulk or a specialty caulk as appropriate.

Some Basic Types of Caulk

100% Silicone

This type of caulk adheres best and lasts the longest, but it sets up quickly, is more difficult to apply and correct mistakes, requires mineral spirits to clean up, and, this is very important, can't be painted. It's best for non-porous surfaces and has a shorter shelf life. Check the expiration date on the tube because if you use one that's outdated it won't cure and will simply leave a mess.

Silicone caulk is not ideal for high traffic areas where abrasion will occur such as a floor.

Polyurethane Caulk

This type of caulk is the great for almost any application, but it can be difficult to use and requires mineral spirits to clean up.

Unlike silicone caulk, polyurethane caulk can be painted and works well on natural products such as un-primed wood. Polyurethane caulk can take up to 24 hours to cure, but stands up to abrasion that would cause silicone caulk to fail.

Because polyurethane caulk dries hard, it is a poor choice for cold weather. Not only does it not maintain flexibility, but it will not bond at low temperatures.

Elastomeric or Acrylic Urethane Caulk

This type of caulk is an excellent choice for most porous surfaces because of its flexibility, adhesion properties, and water clean up. Professional painters prefer this type of caulk because it dries quickly and stretches as much as 200% when cured.

The main drawbacks of elastomeric caulk is cost and ease of application. Because it dries so quickly, you can really only run your finder over it once or twice. Care must be taken to apply a thin bead.

Latex Caulk

Although it tends to be less expensive, latex caulk will harden when exposed to the elements so its durability is questionable and it's not the best choice for exterior surfaces. Latex caulk is very easy to work with and is also inexpensive, but has very little ability to expand.

Siliconized Acrylic Caulk

The most popular caulk and easiest to use, this is a good choice for most applications, but it is still inferior to other options. The addition of silicone means it will stretch, but is still easy to apply and cleanup is a snap.

Butyl Caulk

There are numerous problems with butyl caulks. They're difficult to use, dry slowly, require solvent clean up, and have a tendency to shrink excessively and harden and crack quite prematurely.

Where butyl caulk excels is gutters and downspouts. Butyl rubber creates a watertight seal for metal joints and stands up to weather and temperature extremes.

Within each type of caulk, look for one with a 50 year warranty. It's worthwhile to pay a little more for a better grade of caulk.