Why is weep hole drainage so essential?

Weep hole drainage is essential for the healthy functioning of masonry wall systems in your home.

Without it, water can accumulate within a cavity wall and create damage that can be both costly to repair and dangerous to the health of the home’s inhabitants.

A fully-functioning weep, protected by a quality weep hole cover, can help water escape and allows air to naturally circulate behind the wall’s construction, preventing moisture from seeping into the building envelope.

In this article, we’ll explain why drainage weep holes are so important and how you can make sure that your weeps are functioning properly.

A weep hole on an external wall near a garden bed.

Table of contents

Diagram showing how weep hole drainage works with moisture and water running down the cavity walls, over the flashing and out of the weep holes.

What is weep hole drainage?

Weep hole drainage involves a system of small holes, known as weep holes, that act as drains allowing water to pass through and out of a cavity wall.

These weep drains work with a building’s flashing system, which is a waterproof layer of material that stops water from penetrating inside a building, and channel the flow of moisture in walls toward the weeps.

Weep hole drainage is effective when water passes from the flashing, through the weepholes, and out into the external drainage system.

Why are drainage weep holes important?

Drainage weep holes are important because they help to prevent water and moisture from building up inside a cavity wall. Without them, trapped moisture can lead to structural decay and health issues resulting from fungal growth.

Structural decay of wooden frame materials from moisture damage.

Structural decay

Moisture built up between the inner and outer walls can lead to fungal growths that can decay materials over time and lead to significant structural damage.

This rotting of important timber structures and other materials inside the wall can be difficult to spot, and when it is eventually found, a large-scale repair project may be required.

Mold and mildew growing on internal white wall.

Health issues

These fungal growths can also present a real health issue for the inhabitants of a home, especially those with allergies and asthma.

Mold and mildew are known to cause respiratory problems and other irritations, especially for the elderly or young, and the hidden nature of this issue means that be unaware of the sources of these health issues.

Types of weep hole drainage

There are various types of weep hole drainage systems used in homes with the time and type of construction used usually determining the form. Let’s explore some of the more common forms you may see.

Open-head joints

An unmortared joint between bricks is the most common type of weep hole found in older brick homes and makes for a highly effective weep drain.

They involve leaving a space between bricks that extends their full height, providing a large cavity for water to drain and air to enter and circulate inside the cavity wall.

A weep hole shown in a open head joint between bricks.
A weep vent shown installed in a rendered wall.

Weep vents

Weep hole vents are also highly effective weep hole drainage systems, installed during construction, and more commonly found in more modern homes.

Also known as formers, these units are installed in open-head joints and create a well-formed weep hole that usually has the added benefit of a built-in protective grill to keep pests and rodents out.

Weep tubes

Weep tubes are a less noticeable type of drainage weep holes that involve plastic or metal tubing being mortared in place above the flashing.

However, the small diameter of this tubing means water can only drain out slowly and may also be easily blocked making them a less effective system of weep drains.

Plastic weep tubes.
A screwdriver being used to clear debris from a weep hole.

Ensure your weep holes drain effectively

To maintain effective weep hole drainage, your home’s weeps must be regularly checked and cleared of debris to ensure they are functioning properly.

If they become blocked, by mortar or other organic debris, water will not be able to drain out and will instead build up inside the wall, leading to the aforementioned problems.

To avoid this, schedule a regular check of your home’s weep hole drains, possibly at the same time when you do other home maintenance tasks.

If you find a blockage or obstruction, use a small wire brush or a vacuum cleaner with a hose attachment to clear any built-up debris.

If you’re using a weep hole cover to protect your weeps, be sure to check that its fit is secure and it’s unobstructed.

Finally, be sure to keep the space around your weep hole drains clear, and avoid building any gardens near them or leaving any other objects that could impede their function.

FAQs about weep hole drainage

What are drainage weep holes?

Drainage weep holes are small openings in retaining walls and other structures that allow water to drain away. They help prevent water pressure building up and provide drainage and ventilation.

How do weep holes drain a cavity wall

Drainage weep holes are installed in cavity walls to help remove accumulated moisture. The process uses gravity as water inside flows down the flashing system and exits through the weep holes.

Where do weep holes drain to?

Weep holes drain water to external stormwater systems, a sewer, or even just to the ground outside the structure. It depends on where they are installed and what their intended purpose is.

What happens when weep drains fail?

If your weep hole drainage fails, water can build up inside the structure. This can lead to damp problems and fungal growths that can cause structural decay and health issues from mold and mildew.

Water and rain running down a brick wall.

So in summary

Weep hole drainage is an essential part of maintaining a healthy home.

By allowing water to escape from wall cavities, weep holes help prevent problems like structural decay from fungal growth and health issues from mold and mildew.

Whatever the weep hole drainage system you have at your home, it is important to inspect your weepholes regularly and clean them as needed to ensure they’re clear and functioning properly.

Doing so may prevent you from having to pay for costly repairs, or debilitating health issues, down the line.