Adding footing drain to 50 year old house
I’ve got a pretty big issue with water coming through my stem wall and in general a crawlspace that doesn’t dry out. After getting taken for a ride and paying $5000 to have a contractor do a poor job of installing an interior drain and sump I’ve decided to start tackling the water issue from the exterior.
My house sits on a sloped lot in the Willamette Valley of Oregon and only about 1/2 of it was graded flat when it was built, 1/2 the backyard has a slope and the grade is too high where it is flat in the back with my patio pavers going right up to the siding and the rest of the flat portion generally being above my mudsill height before dropping ~6 inches the 1-2 feet before the house. If money was no object I would probably just grade out the whole flat section to be the correct height and then add a french drain ~4′ deep in the middle of the flat area of the yard (thankfully since I am built onto a slope there’s no issue daylighting drains). However since funds are a bit tight I’m planning on attacking this in stages and fixing one of the biggest areas of water ingress into the crawlspace, the ~25′ side of my house that also has the crawlspace access that allows tons of water in during the winter. I plan on grading out the side yard there so the finish grade is ~8″ below the bottom of the siding and then digging down to the top of my footing and adding 4″ perforated PVC along with gravel/rock and fabric while also putting some kind of waterproofing for the stem wall. I also plan on pouring a concrete wall for the entrance and waterproofing that and running the french drain around that instead of through it. On the end that doesn’t daylight towards the street I plan on running it a little past the corner of the house and then putting a wye on to add a clean out and facilitate connecting to it when I’m able to get equipment out again to do the back of the house.
Now that the details are out of the way I have three main questions:
If I’m only digging to the top of the footing do I need to worry about sloping the pipe?
Should I still put rock/gravel underneath the pipe?
Any issues with breaking up the work like this?
Thanks for any advice you’re able to give!
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Replies
AlexD2022,
Sloping the pipe is better, but as long as it is level it will function fine.
The pipe should have several inches of rock underneath it - and importantly, should be located next to your footing, not on top of it.
Breaking up the work makes sense in your situation, but unfortunately the presence of the new french drain will not alleviate any of the water infiltration problems until it has somewhere to send the water it collects to.
You may find this article useful: https://www.greenbuildingadvisor.com/article/fixing-a-wet-basement
Thanks Malcolm.
I always thought you shouldn't disturb the soil next to the footing? If it's ok to dig down next to it then I don't mind digging the little extra.
Regarding having somewhere for the water to go the plan is to dump it all at the street, I have over 15' from the street to the top of my stem wall so it's no issue draining to the street
AlexD2022,
When you are building a house and excavate to pour footings and stem-walls, you make the excavation all one level and slightly larger than the footing footprint to accommodate the perimeter (french) drains. You don't want to undercut the bottom of the footings, but having the perforated pipes on top of the footing allows water to accumulate against them, and leaves that water at the vulnerable joint between the footing and stem-walls above.
Good luck with your project. It's a lot of work, but pays great dividends.
There are tons of opinions on this topic in various places on this website and in the GBA articles...I am struggling with the same question (but for new construction) and can find valid arguments for all the drain options out there. Local companies don't make it any easier...I have three quotes for three different drain locations, and they range from $5k - $18k.
One comment to the reply below on excavation is that it may also depend on which part of the country the work is being done in. In my area, the width of the footing is determined by the width of the excavator bucket the concrete is poured into the trench without any wood forms so the soil next to the footing is left undisturbed and most builders put the drain on top of the footing. I'm not saying that it is right or wrong but that is what I see around here and am still trying to figure out the best practice for my project.
good luck!
Best practice is to drain the bottom of the footing, like Malcolm says. You want the level of water to be as far below the level of your basement/crawlspace floor as possible.
When you add damp proofing be sure to protect the footing/foundation wall joint, I like peel and stick sheets for this because you can continue the sheet down the wall and over the footing. Getting a product like this to stick to a dirty foundation is another matter however.
I did this same project at my house recently and used a mini excavator, the various articulations of the machine allowed it to dig directly beside the foundation and minimal hand digging was required. With a good operator you should have very minimal damage to siding etc.
I agree an exterior solution is the best option but having a contractor do this job seems likely to cost 3 times as much the interior bid.
Note this will be risky work as one slip of the controls could do a lot of damage. You need to pick your operator carefully.
I doubt breaking the job up into 3 small jobs will lower the price tag.
The new landscaping will not be cheap.
With as much slope as you are describing it seems like fixing the gutters, down spouts and draining away the surface water may resolve the issue.
Walta