French Drain Question

I have a french drain that starts is the middle of back yard and runs vertical about 40’ feet and discharges near curb. I have been considering adding another french drain on the opposite side of home and then run a horizontal drain that would connect the two verticals.

In essence, I would a have U shape french drain configuration. I feel this would reduce the amount of water that ordinarily would have entered crawl perimeter drainage tile. I do not have a crawl problem since I added a 10 mil barrier and six inches of concrete. :wink:

Just looking for additional ways to alleviate the work load of the sump system.

Erol, you lost me when you said it runs vertical for 40 feet.

He is over by Hogwarts:D


Are you on a hillside?

If the crawl has a high water table (standing water in sump pit), there’s not much more you can do to improve the pump use.

Installing exterior french drains (alongside the entire rear of the home) is the ultimate way to go. This will convey any water that does accumulate, out and away from the house/crawlspace.

Why not waterproof the crawl space walls, and give the sump pump some real relief?

Living at the bottom of a hill, this will do very little due to the fact that moisture will go under the footing and still enter the crawlspace…(warned a client that I was building a house for about same…he didn’t listen and we had 12 inches of water in the crawl during a wet season…and it was trapped because the exterior walls were so well sealed)…if you truly want to be finished with moisture in the crawlspace…encapsulate it and be done. (I would still do a french drain on the outside as well)

All due respect Jeff but ‘NO’ way anyone gets 12-100" inches of water in a crawl/basement “because the exterior walls were so well sealed”.

Yes, water could get under or even THROUGH a footing but THAT has NOTHING to do with having the exterior walls sealed or not.Two different things. Just like those who get water in their basement that FIRST enters
through ABOVE grade openings such as open mortar joints,gaps etc around basement windows…this has nothing to do with whether or not water is or is not entering through the basement/crawl walls,two different possibilities/entryways and two different solutions.

Water can get in a crawlspace just like it gets in a basement.One big difference between the two is when there is NO concrete FLOOR in crawl.
Next is,the exterior walls are RARELY if ever waterproofed,absolutely no protection on exterior walls.

Since most crawls dont have concrete floors and most basements do,this is why one can SEE water on dirt floor,unlike having concrete floor where you wont see the water that DOES get under the floor. And so when it rains many who have a dirt floor are going to have/get/see water on floor in crawl and this water could raise humidity level,damp conditions,possible mold on wood and so. Many just need a concrete FLOOR,just like a basement.

Laying visqueen/whatever on-over a dirt floor could help…to a lesser degree it kind of takes the place of having a concrete floor…eh.

ENCAPSULATING a crawl does not stop-prevent water that enters through a wall,does not stop-prevent water that can enter through above ground openings etc. It can cut down water vapor but doesn`t stop-eliminate
water that can get in.

Ill bet yas there will be WATER in MANY crawls that were encapsulated by these goofball inside Cos....UNDERNEATH the visqueen/whatever they put on the dirt floor.Weve seen it because we`ve pulled up the
visqueen etc during/after a rain.Look under there sometime and see for yourself.

At least you’re not in this situation.

My clients home (who has a lawsuit against the builder)…

dunno about you men/women here but i sure get alot of calls,emails on leaky Bilco/whoever doors…sheesh K. I would do WITHOUT.

Dave, nice grade there :mrgreen:

If the blocks and mortar joints are visible through the cement parge coat, the parge isn’t nearly thick enough, and these newfangled spray-on so-called dampproofing coatings are not thick enough either. Of course, in the previous pictures, all that water lying against the foundation right at or maybe above the basement window sill level is going to be trouble, in any case.

I think, but I’m not sure, that I see the images of the block reading through the parge coat, and that appears to be a too-thin coat of dampproofing. Yes, it appears to have been applied by roller or brush, but I’ll bet it’s only one coat, and certainly not thick enough.

I agree with Mr. Bubber that a well-waterproofed crawl space, with a properly installed vapor retarder and a concrete floor, is very unlikely to allow water to enter anywhere. I did see one house where they actually laid a course of block sideways so that the cores were visible…, earth floor, no vapor retarder, it wasn’t parged or dampproofed at all, and the owners wondered why they got water in their crawl space. Duh. When we added on, we waterproofed the outside of that wall so that we wouldn’t get water in our nice new concrete-floor crawl space.

I dont see any downspouts in the picture. Or window wells. The grading has a negative slope twords the foundation. Got Water?

Sorry Kenton, I seem to speak a foreign language late at night…:margarit:

On one side of my home, I have a french drain beginning in back yard (low spot) and discharging at the street. I was considering adding the same set up on the other side of the home and then connect the two which would form a U shape drain.

But now that I have a concrete encapsulated crawl under a 10 mil vapor barrier, would this extra work be worth it?

I’ll answer the same way I do for my clients.

If you’re still getting water then do it. If you think you could under common conditions then do it. If not then don’t.

Drainage doesn’t add value. But it does prevent loss of value due to water.

Here’s the reference I add to my reports when I talk about drainage issues.

I didn’t say that we got 12…or as you added to my quote…100 inches of water into the crawl because the walls were seal but rather that the water table rose which then seeped under the foundation (the walls were dry above the water line other than slight wicking) and became trapped…big difference.

That particular house sat at the bottom of at least 200 foot hill whose slope was approximately 35 - 40 degrees. My suggestion was to not only put a french drain against the foundation but at the base of the hill as well…which they opted against (regretfully).

The way we extracted the water was to put a positive drain at the lowest point inside the crawl…have not had a problem since then.


Are you implying or saying…that by concreting inside a crawlspace that it will alleviate moisture problems…“Many just need a concrete FLOOR,just like a basement.”

Last I checked concrete is porous…as is evident when I use IR to find plumbing leaks in slabs…where moisture has infiltrated same damaging finished flooring…I guess someone forgot to tell water that its not suppose to penetrate a concrete floor. lol

Also…builders as a whole are not going to spend the extra money to concrete a crawl…otherwise why build a crawl at all when you can do a slab…that is penny wise and pound foolish.



PS. Have you ever encapsulated a home…?
I have built basements, slabs, and a boat loads of crawls…both encapsulated and non-encapsulated… IMO, encapsulated is a far advantageous to a crawl with just 6 mil poly sitting on the ground.


You wrote,
…“had 12 inches of water in the crawl during a wet season…and it was
trapped because the exterior walls were so well sealed”.
Thats what you said.

And i replied the fact the exterior walls were sealed has nothing to do with
this 12" or if it was 100" of water being TRAPPED in a crawl. Zero.
YOU said/implied the water was TRAPPED due to the exterior walls being
‘so well sealed’. J krsitams man.

Dont give 2 1/2 craps about what some builders 'think/assume'..... on THIS subject,theyve proven time and again they don`t understand
what they NEED to understand about waterproofing/backfilling etc.

Thats right,some ONLY need a concrete FLOOR!
Take away a BASEMENT concrete FLOOR and you`d SEE the same
puddling/water problems/water vapor as in MANY crawls,yes indeedy sir.

Yeah Jeff concrete is porous…very good. Been through this SAME blcchtt
with other builders,a few finally wake up,not many though.](*,)

What will you very often see ‘IF’ most basements did NOT have a concrete floor? :-k
Whats going to be UNDER most basement concrete floors after-during
a decent rain? :-k


The fact there will be some water under MANY basement floors doesn`t
mean there is this-supposed-assumed high water table blcchttt,no! ](*,)