What happens if window weep holes are blocked?

Author: Orrin Orn IV  |  Last update: Sunday, June 14, 2026

It's not uncommon for window tracks to fill with water occasionally and then drain. Clogged weep holes on the other hand, are like blocked gutters – when the moisture doesn't drain, it can damage your windows, the surrounding walls and trim carpentry (window sills, casing, shutters).

How do you know if a weep hole is clogged?

ANSWER - Having wet grout around the drain does suggest that the weep holes at the waterproof membrane level might be plugged.

What happens if you block weep holes?

Blocking your window weep holes predisposes the window structure to water damage, rust, and corrosion ultimately reducing your window's lifespan.

How do you unclog a weep hole in a window?

Check weep holes at least once a year, before the rainiest season. If they're clogged, open them up with a brush, a screwdriver or a toothpick. Clear away leaves, twigs and dirt that accumulate on the windowsill.

Are window weep holes necessary?

In addition to providing water drainage that keeps rainwater, snowmelt, and melting ice from infiltrating your home, weep holes in window frames serve multiple other important functions: Prevent windows from being ideal breeding places for mosquitoes, flies, and other pests.

How Window Weep Holes Work | Anlin Windows & Doors

Can you block window weep holes?

Blocking a weep hole in a window can have catastrophic results in water damage for the building.

Is it OK to cover weep holes?

While they can provide an entry point for pests, covering weep holes in brick walls is a definite no-no due to the damage this can cause to a building's structure. Instead, high quality screens and covers can be used to keep vermin out whilst maintaining the utility of these very important openings.

What happens if you fill in weep holes?

Sealing basement weep holes can lead to serious damp problems and rot caused by mold and mildew. This can cause extreme damage, often without the occupier knowing it is happening.

What happens if my window doesn't have weep holes?

Window weep holes are easy to maintain. If a window doesn't have them, they can be added to an existing window by drilling a small hole in the bottom of the frame but it is important to know what you're drilling into. This is best handled by a professional contractor.

Can you plug up weep holes?

Danny Lipford: The holes you're talking about that you'll find around the perimeter of a brick home are called weep holes. Now, these are very important and can't be sealed up, because bricks always hold moisture and store moisture.

Can bugs get in through window weep holes?

These important holes are vital for the moisture management of a building but they provide pests with a wide open door into your home. Pests such as cockroaches and mice can use them to enter your home where they can cause damage and create an unsanitary environment.

What does a window weep hole look like?

Weep holes are often rectangular and have a flap covering them. The flap opens one way to let the water flow out of the window and prevent it from flowing back in. Depending on the age of your windows, weep holes may look different. Weep holes serve as drains for water to keep the water from getting inside your home.

How do you check a weep hole?

How to identify weep holes
  1. Look for gaps in the mortar between the bricks: Weep holes are typically small gaps in the mortar between the bricks, located near the bottom of the external wall. ...
  2. Check for patterns: Weep holes are usually located in a pattern of one every few feet along the bottom course of the brickwork.

What happens when weep holes are blocked?

Water Stains or Discoloration: Noticeable stains or discoloration on the exterior walls, particularly around the weep hole area, may indicate water pooling behind the cladding. Mildew or Mold Growth: Excessive moisture due to blocked weep holes can create an ideal environment for mildew or mold to thrive.

Can water enter house through weep holes?

Weep holes are often located at the bottom of brick exterior walls. They look like vertical gaps in the mortar joints between bricks. Because brick masonry is porous, water may penetrate the surface and get behind the wall.

What is the alternative to a weep hole?

As an alternative to weep holes, most new construction will connect the drainage zone to a perforated drainage pipe located behind the base of the wall outfalling to a manhole.

How do you fix a clogged weep hole?

If you notice one is clogged, all you really need to do is to grab a really thin, straight object such as eye-glasses screwdriver. Find the outside exit of the weep hole and gently clear it out with the end of your tool, then find the inside and push any debris through from there as well.

Are weep holes really necessary?

Without masonry weep holes, or if the existing drainage system is blocked or broken, capillary action can result in the water becoming trapped inside the cavity wall.

Can I make new weep holes?

It is difficult to add weep holes after the walls are constructed. If the weep holes are drilled, they will typically puncture the flashing. This is true even if a special guide is placed on the drill. If the hole does not go all the way through the mortar then it will be ineffective.

Can bugs get in through weep holes?

It's important to remember that weep holes aren't only at ground level. In many buildings, certainly in buildings with more than one storey, there will be weep holes at each level. Cockroaches and spiders can come in through these higher weepholes and they are also a favourite entry point for bees and wasps.

Can you partially cover weep holes?

It is also common to see concrete paths or driveways installed that partially or fully conceal the weep holes. This is particularly troublesome because termites are subterranean and can gain access to your home via these covered weep holes without being detected.

What is the main purpose of weep holes?

Weep holes are "openings placed in mortar joints of facing materials at the level of flashing, to permit the escape of moisture, or openings in retaining walls to permit water to escape," according to the Masonry Design Manual.

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