Building a French Drain for a Gutter Downspout

Long shot of downspout and house drain on the left behind the chainlink fence.

From In the Garden

Houston! We have a problem. Whenever I have a problem I think of those five words because problems are never a good thing. This past weekend I have been moving and dividing hydrangeas. The area under my wisteria arbor was not really a good area for the hydrangeas because each summer the area got so dry I just knew the hydrangeas would die. Since one of my two rhododendrons did die from last summer's drought I thought I might rework this small garden near my northwest downspout. Enter one hydrangea that I made into three by splitting the root ball and I'm all ready to plant-right? Well, that's what I thought but then I remember what the evil dog Lady had done to this garden.

Another angle of the two drain areas prior to digging the downspout trench.

From In the Garden

It really wasn't entirely Lady's fault but her digging up two drains in this garden did not help the situation. You see, one drain led from under the house (visible on the outside of the fence just around the turn of the house from the gutter) and the other drain was from the downspout. Both drains had been installed a long time before we bought the home nearly ten years ago. Both drains were clogged up from silt and dirt and one drain even drained INTO the crawl space under the house! It was a mess and a big problem that had to be fixed before any new planting could take place. I knew about this problem last fall but had been putting it off. Well, the day came.

Long shot of house drain in foreground, Coral Bark J. maple, then the new drainpipe for the gutter in the background.

From In the Garden

Here we see both drains laid out and ready for work. I started with the house drain simply because that was the major issue and the harder one to deal with. When Lady dug up the drain I could clearly see it was sloped toward the house. Not a good way to have a drain sloped at all. In the crawl space of our house where the drain emptied there was a huge pile of dirt. It was all from drainage washing back into the house. I knew the drain was there and that it had an issue but simply had not worked it prior to now so I can only blame myself for the big pile of dirt. After scooping all of the dirt out of the crawlspace I tried to clear the drain. It seems the drain was inserted into the foundation to drain away excess water in case water built up under the house. We've never had an issue with this and I honestly can't find any information on house drains. Very weird, but since the builder had installed the drain we felt it should be installed properly and functional. I cleared the square hole (the drain is round) and found a lot of mud in the foundation. I cleared all of that mud down to the footings and removed the old drain. This drain was not only broken due to Lady's digging but it was a corrugated pipe with drain holes. That explained all of the silt in the pipe. Since this drain is to drain water away from and under the house and would hopefully be used infrequently we decided to put in a solid corrugated pipe. It is the pipe closest to you in the picture above.

Outside shot of house drain.

From In the Garden

Here is where the drain exited from under the house. Did I tell you the two gardens affected by these drainage issues house my very tall and beautiful camellia, a large old PG hydrangea, and my coral bark Japanese maple? Scary times for me but the benefit of being a homeowner and a do it yourselfer is you can take care to consider all plants and other extenuating factors. I don't think any plants were harmed but a very large PG hydrangea had a few roots cuts. PGs are very hardy and tough hydrangeas though so it should be okay.

House drain secured in place with concrete vinyl patcher.

From In the Garden

I cleaned the muck and the mess out of the drain hole and from under the house so that any water under the house would drain from the hole. Mr. Fix-it and I then installed the solid corrugated pipe by cementing it into place using concrete vinyl patcher. Concrete vinyl patcher has no stones in it and is smooth. I also used a concrete bonding agent and waterproofed the foundation in the spot as an extra precaution. I think the concrete will work much better for this drain than mud. On the inside we took a different route. The foundation is about one foot wide so the drain goes all the way through and into the crawlspace. On the inside we used 'Great Stuff' crack sealer. This stuff is water resistant and not  waterproof but in my experience it holds up well. If it deteriorates we will be able to fix the situation as necessary. 


The drain was dug to have a pitch of about 1" per ten feet. The water drained well through the trench because I tested it with my hose on full blast when I was cleaning the mud from the foundation. All that was left for this drain was to fill it in with soil once the concrete cured. Oh, if things were so simple.

Trench from downspout with 1/2 gravel fill and landscape wrap.

From In the Garden

Our chain link fence was the next issue we had to deal with. When we moved here nearly ten years ago we had a chainlink fence installed. I use the term loosely because the installers did a crappy job of installing the fence. The posts next to the house were set too close to the house and hit the footings. Therefore the installers did not sink and cement the corner posts properly. This particular fence post has always been an issue because not only was it not set properly but due to the seepage of the gutter water the cement deteriorated to nothing. We could easily pull the fence post out and the dogs were able to get out if they were so inclined. Mr. Fix-it moved the fence post over a few inches, sunk the post and re-poured the concrete to set the pole properly. Now we could turn our attention to the gutter downspout.

Pipe from downspout with gravel, landscape wrap cocooning the trench and gravel.

From In the Garden

Mr. Fix-it dug a positively drained trench away from the down spout to about 20 feet away while I took the truck and trailer to the quarry. If you have a large amount of drainage rock to buy it is always more economical to buy it in bulk from a quarry. The price at my local quarry is $22 a ton. That is a lot of rock. You'd pay about $3 for one fifty pound bag in your local hardware store. By the time I came home with the gravel it was raining so yet another day was wasted. Finally! Yesterday was the day. I woke early and laid out the landscape fabric in the trench. The landscape fabric is to keep soil and silt from mixing in with the drainage rock and the pipe. For the gutter downspout we used a solid pipe close to the house then transitioned to a perforated corrugated pipe further down. The perforated pipe will allow the water to sink into the ground as well as spilling it out into my garden; which is lower than the house at the bottom of the drain.

Competed project. Don't mind the corrugated pipe-it is extra. Hydrangeas, hostas, brunnera, and ginger are all replanted and the garden bed was lightly mulched with pine straw.

From In the Garden

My job was to fill the trench with the drainage gravel, install the pipe (with a sock already on it to ensure double protection against silt and sand clogging the pipe), backfill on top of the pipe with more drainage gravel then cover the whole trench like wrapping a baby in landscape fabric. Once all was sealed up I was able to fill in the trench with the removed soil and sod. 

Mr. Fix-it came home for lunch and used his come-a-long  to pull the chainlink over to the now stabilized pole. We are ever so happy to have that problem worked out since the evil dog Lady likes to escape the backyard so often. Mr. Fix-it would be heartbroken if that dog ran away so he fixed the fence while I backfilled both trenches and dressed up the garden. 


I added the castle rock with cap in order to raise up that side of the garden and to make a water stop. The drainage ditch with the pipe for the gutter is immediately to the right of the castle rock wall. This is basically how the garden was set up prior to the rework but with no castle rock. This area to the crawlspace door must be kept open or I'd have a garden all the way to the deck; which is on the far right of the picture.


Once everything was backfilled and smoothed out I planted my three hydrangeas around the coral bark Japanese maple and replanted a few other perennials I had in this garden; including brunnera and ginger. I also had a ligularia, pulmonaria and a HUGE hosta in the garden. I'm sad to say not all would fit back into the garden. I managed to squeeze in the hosta and ligularia but not the pulomonaria. It kind of makes me laugh because it reminds me of my husband putting together a machine and having leftover parts. Well-I was the one with leftovers this time. 


We are due a huge thunderstorm with some severe weather on Thursday. I can't wait to see how my new drains work....


in the garden....


Have you ever buried a downspout? And if so please share your experiences!

Words and Photos Property of In the Garden Blog Team, In the Garden