Exterior Caulking Tips

A critical part of exterior paint preparation is caulking. If the exterior caulking isn’t done correctly rest of the job will suffer. The best paint in the world won’t be able to perform to its potential if the caulk fails or if gaps and cracks are left open and exposed to water infiltration. The main cause of paint failures is water getting under the paint film.

Properly choosing and applying a sealant will keep out water and remain flexible over the life of the paint job.

Water can do an enormous amount of damage to your home and it is up to caulking to seal all gaps and cracks. It’s best to choose the right sealant. Trying to save money here can, and probably will, cost a lot more in the future.

Plus sealing all of these gaps will reduce air infiltration. The exterior caulking can reduce your utility bill if done correctly. This means a good sealant will actually pay for itself.

I prefer high quality elastomeric caulk when painting a homes exterior. It offers excellent elasticity, adheres to any surface and has a long useful lifespan. Plus elastomerics are water clean up.

Before starting this part of the exterior preparation all scraping, sanding and priming has to be done first. Although exterior caulking can adhere to raw wood, the best results are achieved after priming. Remove all loose caulk before application. This provides a clean stable surface.

Using a Caulking Gun is Easy

Cut off the end of the plastic nozzle with a razor knife. A 45-degree cut and an opening size of 1/8 inch works best. The opening size can be increased for large gaps. If the sealant has a foil seal use a wire or thin nail to puncture it in several places. Professional caulking guns have a wire built into the frame for this purpose.

I will assume you selected a good gun. If not, soon you will be frustrated and running to your local paint store. Buy a good caulking gun before you start.

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Holding the nozzle on the crack or gap gradually move the nozzle down, applying pressure on the trigger. Work towards yourself, this will keep the nozzle in contact with the surface.

The harder you squeeze the trigger the more sealant will be dispensed. Try to apply a thin even bead.

Now run your finger down the crack to smooth and push the sealant into the joint.

For gaps deeper than 1/2 inch use foam backer rod for a better seal. This is a foam rope specially designed for wide or deep gaps and provides backing under the caulk. Available widths range from 3/8 – 1 inch or more.

Elastomeric caulk can handle gaps up to 1/2 inch wide and 1/2 inch deep.

Wide cracks will require 2 applications due to shrinkage. Pre-fill the crack completely then allow to dry over night before applying the final layer. For very wide gaps, greater than 1/2 inches, you can use one part urethane, this can handle the most extreme cracks with one application.

Where to Apply

The importance of fully sealing your home can't be over stated. All areas that can allow water in must be filled after all other preparation is finished.

These areas include open seams and gaps in the fascia boards and soffits, siding gaps, around windows and doors plus their frames. The best seal is over a clean primed surface.

Windows

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Now seal the window to the trim on all sides. Pay special attention to the weep holes do not fill these holes.

Caulking a window requires a complete watertight seal. If the window has no trim, apply your chosen sealant around the entire window. With white caulk a straight and visually pleasing bead can be difficult. Tape can be used to create a straight line.

While applying the tape to the window edge keep the tape 1/8 inch away from the gap. This will produce a better seal. With practice you won’t need tape and caulking windows will become easier.

Another way is to use clear paintable elastomeric caulk instead of the standard white. This caulk goes on white but dries clear and has all the characteristics of normal white elastomeric caulk.

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The header, or top trim, can be two or more pieces of wood. The sill can also consist of multiple wood pieces. Pay special attention to these gaps.

Another area is at the glass and wood edge. This interface can allow water between the glass and wood frame causing peeling and possible rot. Apply a small bead of paintable clear caulking were these two materials meet. The clear caulk can be applied after the window sash is painted. This will allow you to paint the windows a bit faster without having to worry about brushing a perfectly straight line.

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Doors and Frames

Both entry doors and garage doors need extra attention before painting. The obvious areas are the trim to the siding and frame to the trim. Also seal the frame to the threshold. A small bead here can stop problems before they start.

The same needs to be applied to garage door frames. Apply a small bead of clear caulk to the frame at the concrete floor. This will keep the frame from soaking up water and peeling later.

Paneled entry and garage doors require a very good seal. All panels must be caulked after any sanding and priming has taken place. This includes any panels on wood and masonite garage doors.

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Caulking Soffit and Fascia Board Joints

This seems obvious but when high off the ground they are easy to ignore. While caulking this area also caulk behind the fascia board. This provides a very nice finished look.

Caulking Brick and Concrete

Where ever two dissimilar materials meet the gap between them needs to be filled.

This is especially true for wood trim to brick and siding to concrete. Caulking brick should be done with paintable clear caulk. Paintable clear caulk goes on white but dries clear after a few hours. White caulk makes a mess on brick.

For new homes or areas that have never been caulked apply the caulking after the painting is finished. This will make the painting easier and produce a better looking paint job.

The same paintable clear caulking can be used in small gaps where siding or trim meets concrete. For large gaps use either a grey urethane or siliconized acrylic concrete caulking.

Often the exterior caulking is the only thing preventing water damage and rot. You must be thorough, paying attention to the little areas. The entire paint job depends on a good water proof seal.