A rain slit at the bottom of a rain drain. This was placed at the base of a pipe running underneath the concrete walk leading to the front door.
Why are gaps left in the curbing?
Drainage – the importance of proper drainage with curbing in mind.
March 7, 2025
Drainage is essential. From keeping water away from the foundation of your home, to providing a path for snowmelt to drain from our properties, drainage is essential for many reasons.
Proper Grading
A proper landscape design and project will make sure that your property is graded properly so that water always drains away from your home. By grading, it means the ground is slightly sloped away from your home towards a ditch or a channel drain (among others) and directed towards the main street or back alley. These keep water from pooling too close to your home and prevent water from leaking into your basement.
Sometimes homeowners will have garden, tree, or mulch beds that surround the perimeter of their home. This is fine as grass tends not to grow too well in certain locations tucked right near your home so it is nice to have other, more aesthetic elements, as part of the landscaping than dead grass. But with those elements that are then contiguous with grass, you create a border.
Curbing and Water Flow
There are many edging options for great landscape designs, but I’ll focus on concrete curbing because I want to share the way we ensure proper drainage. Curbing is surprisingly good at stopping flowing water. This is because the curbing is generally laid on undisturbed soil which is hard and doesn’t drain very quickly. So with curbing placed on top of that, the water tends to pool in low spots behind (or in front of) the curb. I’ll go through a few ways we deal with this.
Rain slits. The first and most important thing we do is put ½” gaps into the curb at low spots in the yard. This provides a water release point and allows water to exit any area that might be contained by concrete curbing. We like creating rain slits in this way for a few reasons. First, it’s unlikely to clog with mulch, dead grass, rocks, etc. and even if it does, it’s easy to clean out. Another drain style I’ve seen is to drill a hole through the curb. These are hard to clean if they get clogged. Another way I’ve seen is for a slight depression in the top of the curb for the water to flow over. I don’t love this way because it only works when there is a lot of water that has already pooled and sometimes the rock or mulch drains right over top of the curb and then gets all over the grass on the other side. This totally defeats the purpose of the curb! So, we put a small slit throughout the width of the curb that still prevents the movement or rocks or mulch.
But the curbing is supposed to be continuous and then you put a cut through it? You’re right, it is supposed to be continuous. And for the most part, it still will be. Often the slits are at least 15-20 feet apart or more. In comparison to edging stones or other options, the concrete curb still maintains its strength and durability throughout that 15-20 feet.
Rain Drains. An additional option for getting water away from the foundation of your home is the inclusion of a rain drain. These are placed directly below a downspout and contain the water coming from the downspout within the concrete rain drain, and let it flow beyond the curbing. The water goes directly from the downspout away from the foundation of your home. These are great because you don’t need the metal downspouts anymore (Honey! I forgot to put the downspout down!). Sometimes the metal downspouts will get run over with lawn mowers which leaves them squished and not looking the best. A concrete rain drain is styled to match the curbing you’ve chosen and removes the need for the metal downspout.
Questions?
There’s a couple of considerations when it comes to drainage and landscaping projects. However, if you read this and still have questions, please send me a note and I will do my best to answer your question in my next blog post or video.
Thank you very much for reading! Enjoy the beautiful Edmonton summer and soak up that sun! Take care.
Curtis Straub
Owner/Operator
Castle Custom Curbing
Edmonton AB
