There are examples in older homes in Ottawa where the homeowner still has the original driveway and the driveway has sunk so much they have to put in a ramp to drive into the garage. Some have completely given up on parking the car in the garage and are using the garage as a storage room. Most people I talk to attribute everything to high levels of clay in our area. I often hear, “Oh well, there’s nothing we can do about it. We’re on clay”. The truth is something CAN be done about it.

If you think about it, there are skyscrapers in Ottawa that are built on the very same clay soil that your home is built. Drive down a rural area and you’ll often see hugh power line towers standing perfectly straight in the middle of mud bogs and swamps. You can’t get more clay or unsettled soil than that! The truth is there are engineered specifications to deal with building all kinds of structures in all kinds of soil conditions. So why are new home driveways such a problem? What’s being done wrong?

To begin with, no amount of compaction will work on it’s own. You also can’t just let your driveway “sit for a year”, as I often hear, and hope it will settle more. These things might help your driveway last a bit longer, but if you’re sitting on clay soil the inevitable will still happen. The driveway will fail.

Clay is composed of a lot of fine particles. These fine, elongated particles are the main property of clay that causes it to retain moisture. Moisture in the clay expands and contracts during the spring freeze-thaw cycles. What’s needed to strengthen the base for a driveway, or any interlocking stone project, is a way to separate the base and the sub base. To stop the wet clay from migrating into the compacted base. That’s where woven geotextile comes in.

Many contractors recommend a woven Geotextile fabric for under the base, but a lot of contractors don’t even know why they’re using it. They’re doing it because they’ve learned that other contractors are using it and it’s associated with a quality install. I really get a chuckle when I hear a customer tell me that another contractor said they needed a woven geotextile fabric under the base of the driveway to combat weeds. A driveway in Ottawa is often dug to a depth of 18 to 20 inches. The geotextile is below that base. That would have to be some very powerful grass to push it’s way through 20″ of compacted gravel and poke through interlocking stone pavers. If they could make grass that strong I’d buy it and have a beautiful, lush lawn. Heck I’d buy the rights to it and be up there with Bill Gates as one of the richest men in the world–some people will spend a lot of money to have a lush lawn–but I digress.

Some contractors will tell you that woven geotextile is load bearing. Although a bit closer to the truth, woven geotextile does have one way textile strength, that’s not really the intention of woven geotextile. Woven geotextile’s main purpose is to separate the base from the sub base. It stops clay from migrating into the compacted gravel and eroding it over time. We’ve dug up driveways that were twenty years old and you’d swear there was no base there–it’s all mud. That’s because nothing stopped the clay from creeping further into the gravel year after year and eventually completely destroying the compaction in the gravel.

So. Is there a way for builders to build driveways that would last the homeowner more than the warranty? Hmmm….Can you build a hydro tower in a swamp? Or a skyscraper on clay? You bet. And you can bet there are ways to build a driveway base that lasts. It just costs more.

Now home builders are not necessarily at fault and may very well have the best of intentions. There are many home builders that actually follow the specs they have been given. Often times, however, it’s not enough. Often times these specifications are for optimal soil conditions, which are rare in our parts. The specifications for these bases are also designed for asphalt and not for pavers. Since a typical asphalt has a shorter lifespan than pavers (typically ten to fifteen years) it’s long enough to last for when it’s time to replace the asphalt. The idea is you then recompact the driveway and repave and hope to get another ten to fifteen years.

Driveways simply have to be built for the soil conditions they’re being built on and for the intended purpose. In my view, even an asphalt driveway in a new home should have woven geotextile supporting the base. It’s relatively cheap insurance. You still need high proctor density compaction, but it’s a step in the right direction.

So…Unless you live on a rock base in Kanata, you probably don’t have optimal soil conditions. The way I see it you can do one of two things. Ask your home builder if you could pay a bit more for a driveway that’s specified to your soil conditions, or you can move to sandy or rocky area in California where they don’t have clay or polar conditions to contend with and can get by with a six inch base that won’t budge for a hundred years. You’d probably miss the white Christmas, though. Ooops, excuse the political incorrectness–Holiday Season.