Sealing Windows, Doors and Penetrations

A water mark appears at the corner of a bedroom window after the first storm of the winter, and the instinct is to run a bead of caulk around the outside of the frame. Sometimes that is exactly the right fix. More often it is a fix for the wrong layer.

Every opening and every pipe in an exterior wall is a hole in the waterproofing, and a house relies on several layers to deal with each one. Sealant is the layer you can see.

Is caulk enough to stop a window leak?

Only if the leak is at the sealant joint. A window is protected by its own frame and drainage, by flashing and building paper lapped behind the stucco, and only then by the sealant around its face. When water gets past the flashing or comes down through a crack above, caulk on the outside cannot reach it. Finding the entry point comes before sealing anything.

How a window keeps water out

On a stucco home, a properly installed window has, from the inside out:

• The window frame itself, with a track and small weep slots at the bottom that let water collected in the frame drain back outside.
• A nailing flange around the frame, lapped with flashing tape and building paper so that water running down the paper behind the stucco is carried over the window, not behind it.
• The stucco, finished up to the frame.
• The sealant joint where stucco meets frame, which keeps most water out of that seam to begin with.

On a home built that way, the sealant joint is the first barrier, and the flashing behind it is the one that really matters. Neither the paper nor the flashing can be reached without cutting into the stucco.

Retrofit windows: where sealant does more of the work

Across the older tracts of Chula Vista and National City, a great many original windows have been replaced with retrofit units. These are set into the old opening, often over the old frame, without removing any stucco. It is a sensible way to replace windows, but it means the original flashing stays behind and the new window’s connection to the wall depends heavily on the sealant joint around its outside edge.

On a retrofit, that joint is worth inspecting at every repaint and replacing when it has cracked, shrunk or pulled away. It is doing much more than tidying the paint line.

Doors and thresholds

Doors leak lower down. The usual places are the bottom corners of the jamb, where water wicks into the end grain of the wood, and the joint between the threshold and the floor or slab outside. A door sweep that no longer touches the threshold lets wind-driven rain straight in.

Sliding glass doors have their own drainage in the bottom track. When that track fills with dirt, leaves or sand, as it does near the coast, water backs up and overflows inward. Keeping the track and its weep holes clean prevents a surprising number of “leaks”.

Wood doors and jambs in older homes, which are common in La Mesa, deserve a closer look at the bottom of every jamb. Soft wood there is a repair, not a sealant job.

Penetrations: every pipe, vent and box

Every item that passes through or mounts onto an exterior wall needs its own detail:

• Hose bibs and plumbing pipes, where the stucco around the pipe often cracks.
• Dryer and exhaust vents, which should have a flanged hood sealed at the top and sides.
• Electrical boxes, conduit and outdoor light fixtures, sealed at the top and sides with the bottom left open to drain.
• Air conditioning line sets, often packed with expanding foam that crumbles in the sun and opens a gap.
• Cable, phone and satellite lines, frequently drilled through the wall and never sealed at all.
• Gas meter and service pipes at the base of the wall.

Each is cleaned, the old failed material is removed, and the gap is sealed with a sealant made for exterior movement and for the two materials it is joining. The types of caulk and where each one belongs are covered in more detail in our article on caulking before painting.

Finding a leak with a garden hose

If you have a leak you cannot place, a careful hose test in the dry months will often find it. It takes two people and patience.

1. One person goes inside, at the spot where the water shows, with a flashlight.
2. The other starts low outside, wetting only the bottom of the window or door with a gentle flow, not a jet, for several minutes.
3. Move up in stages: the sides, then the top, then the wall above, giving each area several minutes before moving on.
4. Stop as soon as water appears inside, and note exactly which area was being wetted.
5. Never spray upward under flashing, a sill or a lap. That forces water where rain would never go and creates false results.

If the water appears when the sealant joint is wet, the joint is the likely cause. If it only appears when the wall above is wet, the problem is higher up, and caulk around the window will not touch it.

When it is not a sealant job

Water entering through cracked stucco above a window, through failed flashing, or through framing that has already rotted needs repair rather than sealant. Stucco and wood repair is part of what Ebenezer does as part of a project, and for anything that belongs to another trade, he will tell you plainly instead of sealing over it.

The time to deal with any of this is the dry season, when joints are dry enough for a sealant to adhere and cure properly before the first rain arrives.

Sealing is part of the waterproofing service, and the older housing of National City is described on its page. If a window or door has started to leak, ask for a free estimate and Ebenezer will find where the water is coming in and tell you whether a sealant joint will solve it or something behind it needs attention.