Moisture is your building’s silent enemy. When rainwater infiltrates your brickwork or condensation gets trapped behind a window, you risk mold and mildew growth, cracks, and similar headaches that require expensive repairs. Luckily, the commercial construction gods saw this problem and smiled down upon us, giving us the easy solution to the moisture issue: weep holes.
In this article, we’ll cover all you need to know about weep holes and the through-wall flashing that makes them work, giving you the information required to keep your walls and windows in top-notch condition and avoid costly fixes down the line.
Quick Answer: Weep Holes and Through-Wall Flashing
A weep hole is a small, intentional gap that allows water or air to drain from enclosed areas, like a wall or window. In walls, through-wall flashing helps guide built-up moisture toward your weep holes for external drainage. Without these systems, your building is vulnerable to structural decay and mold growth, the latter of which could cost between $1,200-$3,800 to repair.
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What Is a Weep Hole? Types and Application
A weep hole (sometimes known colloquially as a water weep or, verbally, “whip hole”) is a crucial drainage element that directs water and air out of your building’s structure while reducing hydrostatic pressure. These small but mighty features appear in a variety of contexts, including:
- Brickwork: Brickwork weep holes appear as small gaps between bricks in the base of brick veneer walls that let moisture and air escape. They’re usually spaced 24-36 inches apart and have a vertical, slit-like shape.
- Windows: Window weep holes are small slots in the bottom of window frames that drain moisture from condensation and rainfall. These are especially crucial because water frequently infiltrates window frames during heavy rain, causing rot, cracks, and bowing.
- Sump Pumps: Sump pumps are the devices in your basement or crawl space floor that drain water outside in case of flooding. Weep holes for sump pumps are commonly drilled into sump pump discharge pipes to prevent air lock—in other words, they stop air bubbles from halting the flow of water through the pipes and out of your basement.
- Retaining Walls: As well as allowing rainwater to exit, weep holes in retaining walls alleviate hydrostatic pressure, a force created when water is held back by a barrier. Left unchecked, this pressure can crack or destabilize the wall. So, by reducing it, weep holes in retaining walls help the barriers last longer and stay structurally sound.
- Water Pumps: Weep holes are often found in mechanical water pumps, such as those in cars and trucks. Weep holes in water pumps serve a slightly different function that other types of weep holes, acting as an early warning system for pump seal failure; if you notice oil or coolant leaking through a water pump weep hole, take it as a sign that you need to fix your oil or coolant seal, respectively.
See the table below if you want to compare basic information on these five applications:
Application | Weep Hole Purpose | Key Details |
Brickwork | Drains water from behind brick veneer walls | Small vertical gaps between bricks, typically spaced every 24–36 inches |
Windows | Channels moisture out of window frames | Slots at the bottom of frames; crucial during heavy rain to prevent rot and warping |
Sump Pumps | Prevents pump air lock | 1/8″ hole drilled in discharge pipe above the pump to keep water flowing |
Retaining Walls | Relieves hydrostatic pressure | Openings at the base let water escape, reducing the risk of cracks or wall failure |
Water Pumps | Acts as a seal failure warning | Found in mechanical pumps (e.g., cars); coolant or oil leaking indicates a failing seal |
What Is Through-Wall Flashing?
Through-wall flashing (also known as thru-wall flashing or through-the-wall flashing) is the hidden partner of weep holes, particularly in brickwork. It’s a copper or stainless-steel barrier installed inside masonry walls that guides water toward weep holes.
- Purpose: Collects water that seeps into the wall cavity and directs it outward.
- Placement: Around vulnerable areas such as roof-to-wall intersections, doorways, and window openings.
- Function: Works with weep holes so water exits predictably instead of soaking into interior walls.
Without flashing, water may bypass the weep holes and infiltrate your working space or even stay within the wall, causing mold growth and structural issues.
Why Weep Holes and Through-Wall Flashing Matter
When weep holes and through-wall flashing work together, they make a meaningful impact on your building’s longevity. Here are some of their core functions:
- Preventing Structural Damage: Retaining walls and brickwork without weep holes often crack or even fail under hydrostatic pressure.
- Improving Indoor Air Quality: Standing water behind walls promotes mold and mildew.
- Extending Building Life: Dry brickwork and wood lasts decades longer than their wet counterparts.
- Supporting Energy Efficiency: Insulation materials such as foam and wool lose much of their performance when damp. By keeping wall cavities dry, weep holes and flashing help you prevent heat loss and save money on your AC bill.
To put it simply, if you want to save money on costly repairs and add to your building’s lifespan, ensure your brickwork and windows have well-maintained weep holes. But, how do you maintain weep holes?
Common Problems with Weep Holes
When neglected, a variety of issues can arise with weep holes:
- Clogging: Dirt, mortar droppings, and other debris can accumulate and block water flow.
- Caulking and Painting Over: Sometimes mistaken for cracks or flaws, weep holes are faultily sealed by caulk or paint (that’s why having an experienced commercial contractor is so important).
- Pest Intrusion: Without covers, insects or rodents may enter wall cavities, and some insects may even build nests in your weep holes and the spaces behind them.
- Fires: In wildfire-prone areas, wind may pull embers into open weep holes, creating an unexpected ignition hazard.
Recognizing and addressing these problems early is the name of the game when it comes to weep hole maintenance. To that end, be sure to inspect and clean your weep holes once a year to keep them functioning properly.
A Note on Weep Hole Covers
Weep hole covers (or their variations, including weep hole vents, weep hole screens, and weep hole guards) are small accessories placed over or inside the openings, particularly in walls and windows. They serve several functions:
- Preventing pest entry: Covers keep out insects and rodents that might nest in wall cavities.
- Blocking debris: They stop leaves, mulch, and dirt from clogging the drainage path.
- Maintaining airflow: Most covers are designed with mesh openings so air can still circulate behind the wall or frame.
- Fire safety: Certain covers, especially those sold in areas where wildfires are frequent, are meant to block embers and prevent fires from starting in your wall cavity.
Weep vents for windows and brickwork are especially important, since these are common entry points for pests and often sit at ground level. For property owners, checking these protective inserts yearly and replacing broken or missing ones can prevent larger drainage system failures down the line, saving you thousands of dollars in repairs.
Weep Hole Maintenance Checklist
To help you keep track of your wall and window maintenance goals, we’ve compiled the following list of tasks to be completed each year:
- Inspect weep holes and covers for obstructions such as dirt and vegetation.
- If you find any debris, gently clean covers with compressed air or a toothpick to ensure the slot stays open.
- If weep hole covers are damaged or missing, be sure to replace them (you can find weep hole covers at many hardware stores).
- For sump pumps, make sure the drilled weep hole in the discharge pipe stays clear of mineral buildup. This is one of the most common causes of pump failure during heavy storms.
If you follow these tips, you can avoid any costly headaches stemming from weep hole neglect.
Frequently Asked Questions (FAQs)
Weep holes direct water out of holes in a brick wall or window frame, preventing structural damage.
The flashing is the waterproof barrier inside the wall, while the weep hole is the outlet. They must work together to keep your walls and windows dry.
No, because sealants block drainage. A better solution is to use weep hole covers instead.
Usually every 24-36 inches, depending on your local building code.
Air lock can stop it from discharging water, leading to flooding
Sump pump weep holes are usually made in the discharge pipe above the pump itself.
A retaining wall weep hole allows water to drain and reduces hydrostatic pressure, which helps prevent cracks and wall collapse.
Final Thoughts: Your Building Needs Weep Holes
From brickwork weep holes and window weep hole covers to sump pump weep holes and retaining wall weep holes, the principle is the same: water needs an exit path. Combined with through the wall flashing, these small openings form a fundamental part of your drainage system that can save you thousands of dollars in repairs.
Are You Looking for a Commercial Weep Hole and Flashing Contractor?
If you need expert help maintaining or repairing your weep hole and through-wall flashing systems, reach out to Baker Roofing Company. For over 110 years and across the American Southeast, Baker Roofing has offered premium commercial roofing and flashing services in line with our motto of “Always Good Work.” If you want an issue-free commercial property, request a free quote below. Let’s build something that lasts.
