Here at Weepa we receive many calls from home owners who are either worried about, or have been told that, the damp and moisture problems in their homes are caused by the entry of water through weepholes.
In 2010 we commissioned research by Griffith University to investigate whether this was possible. This research demonstrated that even under truly extraordinary conditions water rarely enters the weephole and even if it does it cannot be blown high enough up in the cavity to create internal damp problems.
To understand why, it’s important to look at the details of a correctly constructed cavity wall. The diagram below shows the location of flashing which extends from underneath the weephole upward to contact the internal skin of the cavity. You can see that this flashing functions to guide and drain any moisture which might enter through a weep hole straight back out again.
At this point you might be asking “Well what is the problem and how do I fix it?”
If you have damp and moisture problems with your walls it almost certainly comes from a different source. Furthermore, if you block your weep holes in an attempt to solve that problem then you will prevent the drainage of that water and the airflow needed to completely dry the cavity. This will likely cause catastrophic problems.
The possible culprits are:
1. Flashing or waterproofing problems around windows and doors. This is the most common problem. Flashing is a waterproof membrane designed to channel water to the exterior of your home. It runs from the inside skin surface to the exterior skin surface in the cavity and is found around windows and doors and also around the house just below the weep hole on each level. It is a critical component of your home and just one small area missed in construction can cause damp problems which are very hard to find. The resultant damage is usually above or near the problem but not always. We have heard of cases where poorly installed flashing on a top floor rear window had caused flooding at the front of the house. Horizontal members directing water throughout a structure can cause this.
2. Faulty roof installation or corrosion.
3. Faulty plumbing.
4. Unintended conduits from the outer skin to the interior such as incorrectly installed brick ties or incorrectly drained airconditioning units.
What to do next?
The first step is to locate the highest point at which the interior wall is damp. Storm water and accidental flooding moves downward through the wall so the source of the water is almost certainly above the visible dampness. An infrared camera can greatly assist at this stage. These cameras reveal where the wall is cooler and thus the source of the water.