How to Make a French Drain

This is neither a glamorous food post nor a pretty garden one, but a practical, home maintenance piece that will hopefully give you the courage to ‘do it yourself’, if necessary.

We came home from about a ten day holiday after there had been crazy, wicked storms reported in our neck of the woods: thunder, lightening, and rain producing flash floods in isolated areas.  I watched garden carnage pictures flash up in my gardening groups every few days and wondered about the integrity of our garden.  I did not, however, think of our house (aside from those little pangs of worry about security and leaving your house for an extended period of time that most people probably have, but we had the in-laws & neighbours looking in on the place, so I didn’t sweat it, too much).

The Situation

We live on a steep hill, near the top, so water tends to drain away from us.  We survived the June rains of 2013 that led to massive overland flooding in Calgary without a hiccup, so we thought we were in the clear with respect to water management, in spite of the fact that the uphill side of our property had a concrete path along its length that had significantly frost heaved over the years, making some of the path angled towards the foundation, instead of away, especially at the NE corner of the house.  Plus, any issues that our uphill neighbours had, would drain our way by way of gravity, compounding matters.

We’ve had a lot of rain in Calgary, of late.  I heard a number go around a few weeks ago that we have already received 90% of our annual rainfall, most of it in the preceding month or so.  The soils are unusually saturated.  There have been a series of events that have led to the soil alongside of our house being particularly saturated.  I think that it all started one evening, the week that our uphill neighbours took possession of their new home.  They weren’t yet living there – first refinishing the floors and such – and we had a massive hail and rainstorm that ripped off their downspout adjacent to our property and we were outside with the snow shovel, pushing water off of our concrete path, with no way to contact them, so we rigged a big Rubbermaid container as a catchment basin for all of the water coming off of their roof, tipping it to flow away from the side of our house and down the front of their property as best possible.

The Damage

Successive storms have resulted in small leaks in their basement, but we were okay.  Until, that is, we went away on holiday.  And, in all reality, there is a chance that our flood occurred a day or so after we got back, when we had localized flash flood conditions in our neighbourhood.  There was so much rain and hail.  Not big hail, mind you, and it was more rain than hail.  Regardless, it was too much for our drainage system to function properly and water was pouring over the eavestroughs.  The same thing was happening to our uphill neighbours and since water follows the path of least resistance… it all pooled in front of one of our basement windows where the concrete path was just begging to hold the water.  It appears that enough water pooled there and then it followed the next path of least resistance: entering our basement through the window.

Our basement is finished but we ripped up the carpet when we moved 01e157e4e6937b26917f53df497066992db097b1ddin as we couldn’t get it to shake its pack-a-day habit from the previous owner, so we were blessed with just a flooded concrete slab.  I did have some of those giant foam kiddie square tiles down to insulate the floor a bit and it was when I was heading to the storage room to grab something, I stepped on the foam tile and realised that it was floating and went squish upon contact with my foot.  There must have been at least 10 L of water on the floor and I’m happy to report two things: our concrete slab is not perfectly level and the new flooring I had purchased in the spring is still dry in its boxes, waiting patiently to be installed.  Phew!

We have a dehumidifier running in the basement for now and have yet to survey the internal wall damage as we wanted to get a hold of the external issues and stop them dead in their tracks since we were still having rolling storm cells pass by, we wanted to finally correct the drainage issues along the north side of our duplex.  So, the next step is to make some test holes in the dry wall to check and see how wet the insulation is (if there is any insulation, ha!).

The Project

Removing the frost-heaved concrete path was on our to-do list when we first looked at the house, 5 years ago.  It was still on the list when we bought it.  Then we moved in after having moved from another province with an 8-day old baby and I couldn’t really walk due to some nerve damage (another story).  Needless to say, we were keeping things as minimal as possible and the fact that we had moved from the coast to dry Alberta wasn’t exactly motivating with respect to correcting water-related issues on our property.  There was also no sign of water damage anywhere (although that could have been hidden).  And, then about a year and a half later we survived the June 2013 flood weather unscathed, so we boldly assumed we were in the clear and would do the job at some point, but at this point, we were now busy with two kids, trying to have some fun, and finishing up kitchen reno tidbits, etc.  There’s always something right?  Right.

We needed to remove the path and build a French drain.  A French drain isn’t French, but named after a guy, and it is simply a special ditch with piping wrapped in gravel at the base of it, designed to help water flow.  Our ditch is about 2′ away from the house, at the base of the small hill that’s on the property line, so it will catch any water that flows from the uphill side, as well as any overflow from our eavestroughs, and then it is angled as such to carry the water away from the house to the front of the property, where it ends in a gravel filled bowl where water can percolate into the ground (or overflow into our new garden).

Step One: Dig an Emergency Ditch

One day I found an hour or so to muck out a quick ditch to help hold any excess water away from the window, in case we had another flash flood style storm again.

emerg ditch close

Step Two: Remove the Concrete Path

We rented an electric breaker (small jackhammer).  We were recommended to rent a pneumatic jackhammer but there wasn’t one available, so I think that would have made the job easier, but the electric breaker worked for our 18″ x 4′ x 4″ slabs.  The key to this job was working in small increments, placing the bit only a few inches or so away from the last crack.  Once we could get some space underneath the slabs, we could break off bigger chunks.

This process created a lot of waste in the form of chunks of concrete.  Thankfully this waste is recyclable (here, at least), but we chose to re-purpose it, instead, by building two retaining walls for new perennial gardens in the front yard.  So, this was my job: I built a dry stacked “rock” wall and the idea is to stuff the more open crevices with sedums, strawberries, and other hardy groundcovers.

rock work 4

My mum looked after the kids all morning and we managed to finish the breaking in one day.  Once this part of the project was finished we both exhaled a huge sigh of relief; this had been a big hurdle for us to get over, mentally, as we aren’t much for using big power tools.  I finished the quiet dry-stack the next morning.

Step Three: Dig

My husband was the champ here.  He dug most of the 40′ trench, which was almost 3′ deep at its furthest point as the end point of the ditch is actually higher than the starting point.  The front of our property has quite a mound that has developed, between tree roots and grass accumulating over the years.  The ditch needed to slope at least 1″ down for every 8′ to facilitate the movement of water in the direction that we wanted.  And, it needed to be at least 1′ deep.  So, it started at 1′ deep on the west end and progressively got deeper as it headed eastwards, with only our toddler’s head poking out when all was said and done.

The trench ends in about a 1′ radius cylinder that we will fill with rock.  As it is against City by-law to dump water run-off on to their property (i.e. sidewalks and streets), this provides a reservoir of sorts for the water to go to and even spill over from.  Normally, any water that reaches this point will percolate back into the ground.  Worst case, the hole is placed where any spillover will run into the garden or will slowly trickle down the hill at the very front of our property, with most (if not all) of it ending up back in the ground before it hits the sidewalk, let alone the street, even in a major storm event.

Step Four: Lay the Pipe

We could have used weeping tile, but decided to go with rigid PVC sewage pipe for our French drain.  Since our trench is straight and long, it was super easy to work with, easy to level, and more durable than weeping tile, which can be prone to being crushed, especially under pathways.  The other benefit is that the PVC is rigid enough to be scoped if it ever needs to be cleaned of tree roots, etc.  Since the pipe passes a spruce tree and runs under the canopy of a green ash, we figured that this was super relevant for us.  So we put a 90 degree elbow on the west end of the pipe and a screw top lid on top, keeping the dirt out but allowing us access in the future, if need be.

It was recommended that the other end of the pipe also have a 90 degree elbow (or just bend weeping tile upwards, if you use it), but our hole was so deep at this point, it made more sense to just have the large cylinder, itself, act as the bend in the pipe.

But, first, we laid water-permeable landscape fabric down, then a layer of drain rock, and then the pipe, checking to make sure that it was not level as we went!  (Ideally, one would rent and use a laser level or a surveyor’s transit; we used a long spirit level along our rigid pipe.)  We then covered that in more drain rock and then wrapped the landscape fabric around it.  This landscape fabric barrier will function to keep out fine particulate matter, helping the pipe to run free and clear, and should also deter tree roots to a certain extent.

The rest of the ditch can be filled in with more gravel and other sized rocks to create a beautiful dry river-bed look, or you can use mulch.  We have decided to use mulch and are awaiting a truck load (10-12 cubic yards) of free mulch from a local arborist to finish up our project.  Down the road, I think that I would like to use rocks, but that is a lot more work and a tonne more money (pun intended, of course) and is just not in the cards right now.  (I would also like to build a part-shade garden here with hostas, ferns, ligularia, pulmonaria etc.)  The mulch is super functional, too, such that it will actually hold water and will help to build soil diversity.  And, did I mention that it’s free?

Step Five: Building up the Garden

Calgary substrate is predominantly clay.  Pure clay buried under some clay loam.  We excavated a lot of clay and clay loam!  One more thing to go to the dump…  but, instead, I am experimenting with it because I can’t bear to take this mineral rich substance to sit in a landfill.

pano new garden start

I used the purest of the clay to smother grass, which I will then cover in cardboard before adding a few inches of aborist’s mulch.

I grabbed a bunch of the clay loam and put it in the bottom of the new beds, as fill, and dumped zeolite alllllll over it.  I will not incorporate this into the new bed, but rather leave it there and let the zeolite and worms do their magic underneath at least 4″ of pure compost, which will then be topped with a garden mix (peat/compost/soil), and mulch.

It’s a good time of year to build perennial beds here as plants are a good size to be divided and there are lots of sales!  I picked up a bunch of perennials and shrubs 30% off and am going to plant them this week.  They will need some love and water, but will most likely turn out just fine.  I picked only super hardy (Zone 2 and a couple of Zone 3) plants for two reasons: they won’t have much time to establish before winter and I’ve started to hear rumours that we are going to have a really harsh winter.

We have managed to get rid of all of the grass in our front yard, now, hip hip hurray!  There is only the grass on the city easement that we are responsible for (and will slowly take over and plant with local and fruit-producing shrubs, mixed with hardy, self-seeding, perennials, like flax and rubdeckia).

Conclusion

The boring structural-integrity type projects of home ownership are super important, even if they don’t look like much.  Lesson learned… for now!  If you do them, you might not have to miss out on your long-anticipated holiday to Revelstoke to hang out with your awesome friends, spending your days doing manual labour instead.  Learn from us!

In addition, French drains are the perfect do-it-yourself kind of project.  I crowd-sourced in my fabulous gardening groups and got some great, sound advice (especially from Jason at Leaf Ninjasthank-you! – get them to do the work for you if you don’t want to DIY) and will now sleep better knowing that there is a solid water management plan in place on our property.

If you are planning a similar project, please feel free to ask questions!  I can’t promise to help as I am no expert, simply sharing out experience here to help other people, like us, when consulting the interwebs for advice on DIY projects.

Although we still have a lot of mulch to move around, we are nearing the end of our project and feel a pretty good sense of accomplishment (and relief!).  So, go for it, if you are contemplating DIY, it is totally doable, in my humble opinion.  Or, look around for a local permaculture design company to help you design, and possibly implement, water management solutions for your unique property.

What have you gleaned from this? Questions? Comments? Please reply here: