We have a bi-level home on a hill; recently the garage, which is about
6' under ground, has been taking on water after a heavy storm. The
house is on a slope, and we know that hydrostatic pressure is the
culprit. We asked 4 contractors for ideas/bids and all suggested a
French drain-sump pump set-up, which seems like the correct way to go.
The sticking point is this; the garage is a 2 car, divided by a
cinderblock, load bearing wall. One contractor says he can just go
through that wall, and around the perimeter of the garage. This makes
the job much less expensive, instead of going around 6 walls with the
drain, he is going around 3, so the linear footage is much smaller. He
says, the hole that would be cut through the load bearing wall is
insignificant, and will be recemented anyway. I tend to agree with
him after thinking about it, but I do not want to wake up with a
collapsed/cracked wall one day! I would love to hear everyone's
How is the garage situated in relation to the rest of the house? House
in relation to slope?
I don't understand the 6 walls. If uphill is at the back of the garage,
then it would seem
that a drain across that wall would keep the water out of the garage. I
know I'm missing
Yes, tough to explain without picticures!
Where the water problem occurs is at the back of the house/garage. We
sit on a hill. The entire property slopes
down to the street. The garage is on a slab 8" below the slab that
leads to house. No problem with water on that
level. The garage has a slight slope that tilts toward the the back of
the house, not towards the garage doors.
You are not missing anything. Drain across the back wall is
absolutetly correct. The load bearing wall I mentiond intersects the
What the contractors all said, (in unison, I might add)is that the
other walls need drains as well.
If you were looking from above, left wall is an outside wall, so that
would kind of make sense to me.
The one contarctor, as I mentioed, just said, do the ouside wall, back
wall, and 5' up the inside wall.
Are you saying the back wall drain wouldbe sufficient? It's really not
a a lot of water that we get, and it's sporadic at best.
The "6" walls come from doing the left, back in garage 1, up the
center (LB wall), down the LB wall, back in garage 2 and 5' of the
Thanks for the input.
if your asking about a 2 or 3 inch drain line thru a concrete load
bearing wall thats common and wouldnt effect the wall strength.
around here interior french drains between sides of load bearing walls
are dug under the footer. its no trouble water finds its own level.
you should try for a gravity drain to daylight if at all possible, so
power outages and pump failures never can cause a flood.........
No......I don't know enough to tell you what is right or wrong. My
thought is this: the problem is
with heavy rain and is sporadic. That suggests to me that the slope is
bad and you are getting runoff.
not groundwater. If that is the case, then stopping or diverting the
water so it runs away from the garage
might cure the problem and, at worst, just require a french drain across
back of garage to........? In conjunction
with that, a little grading and/or addition of soil across the back to
minimize what reaches the area in back
of the garage..
Sounds like something that looks great on paper :o) Where is the water
supposed to wind after
it is collected?
Being in the epoxy coating business, I might suggest sealing and
waterproofing the wall with epoxy paints. Outside would be best
the could also be done coating the inside of the wall.
very similar to coating sewer manholes - they get coated inside
because you don't want groundwater/surface water entering the
manhole and 'overflowing' the system.
My opinion is to regrade the back yard, and put in a swale to redirect
the water around the garage. If that isn't enough, bite the bullet, and
dig out the backfill on the outside of those 2 sides, and put in a
proper foundation drain, with proper gravel and whatever above. While
the trench is open, replace the waterproofing on the outside of the
wall. Interior french drains are a second-best solution in a basement,
where the floor gets almost no load. But putting them in a garage,
thereby breaking the link to where the slab sits on the footer, seems to
be asking for trouble. Not to mention, how warm does the garage stay?
Ever get cold by where the big doors open?
IMHO, water should be redirected or stopped outside the basement wall.
(Yes, I just had a site survey from a 'reputable' basement waterproofing
company, and even after I told him I grew up in the business and knew
better, he still tried to sell me snake oil. As he was packing up, he
even tried to offer me a discount if I would sign a contract and give
him a check right then.)
But having said all that- no, a small hole in the bottom corner of the
dividing wall, to tuck a tile under there, won't seriously affect the
load-bearing capacity. I assume you have a door through the wall
already? Just stay away from right under the door frame.
From one who has gone through the drain problem from you know where, may I
say that your suggestions are the first ones that make any sense.
Gritz has tried to describe his problem, but it is a bit difficult to do so.
And I can understand that.
Your comment about french drain people selling snake oil is absolutely
right. They wanted to do that on my property for $1-2000. The last owner
sold rather than deal with it. I decided to do it myself. I found my
problem was caused by construction fill of a deep ditch between my house and
the neighbors; the street slopes downward toward me and the lawns are even
with the curb. As I said, apparently before the houses were finished there
was a big ditch there until they filled it in. The problem was that they
used construction sand: very porous.
After digging it all out, I could see that the groundwater would go six feet
under the surface, then under my crawl space, which was like a swamp. The
french drain guys wanted all that money to dig a 24" french drain. A lot of
good that would do!
Like your suggestion, I dug out around the house. The crawl space had been
filled in with concrete block some years ago, but it wasn't sealed very
good. I sealed and waterproofed it, then put a border of 4mil vinyl
sheeting on it before I filled it in.
Where the snake oil guys would have put a 24" french drain, I dug a
50'X2'X6' deep trench, put a 4" socked slotted pipe at the bottom, then a
sheet of 4mil vinyl along the side of the trench. The pipe went around the
house to the lower side, where I got permission from the city to put a drain
in the curb. I tied my gutter drains and a basement drain into it.
This drastic fix works. We've had less than moderate rains so far this
spring and haven't had any for nearly a week, but that drain that comes out
of my curb is still running down the street today. It shows no sign of
They would have put in the french drain and missed all that water!
Oh, by the way, that crawl space is dry as a bone, even in rainy weather.
The partial basement, which used to be slimy, is now dry as a bone.
I am the other half of your success...................... failure.
heres what we tried.......
had foundation mostly dug out to footer level, found old drain line
clogged completely, water proffed walls, installed new drain line, and
many tons of gravel since we had to remove all the sidewalks and steps
that suurrounded a good bit of the home. then regraded entire yard,
installed new downspout drains going to street and daylight, replaced
If it hadnt been DIY it would of likely cost 20 grand...........
Well the water no longer bothered the walls but still came up thru
floor with every heavy rain........
had interior french drain installed, that fixed it finally............
conclusions exterior work costs a fortune and may not be
the costs for backhoe, gravel, dump truck to haul away excess dirt the
gravel replaced, rebuilding lawn, tons of hard labor,new sidewalks and
steps, well it all looked nice and gave the home curp appeal, we sold
it some years later.
but the interior drain worked better and only cost 3 grand.
sometimes water table actually rises and all that exterior work is a
grand waste of time and money/
smart builders install interior french drains in new homes, today its
frequently a building code requirement
Builders in your area still offer basements? They have mostly vanished
around here. (I think it is stupid, but that seems to be the way
'standard practice' is heading.)
2 different problems- surface water saturating the topsoil and coming
through wall, and high groundwater levels. A lot with high groundwater
really shouldn't have a basement, but if a basement is considered a
'must have', and lot can't be resculpted accordingly, yes, interior
drainage may be the only way to go. I remember a McMansion on north side
of Indianapolis I worked on in early 70s- no other house in the sub had
a basement. Thus guy <absolutely> insisted on one. The hole kept filling
with water. We finally put in exterior and interior perimeter tiles, an
X of tiles across middle of slab, a 5 foot deep 30 inch sump pit to
collect it all, with an overflow tied to an exterior sump pit (really a
precast manhole) in front yard, that could be used to pump from in an
extended flood situation.
I still say water should be redirected or stopped outside the basement
perimeter. If that can't be done without heroic measures, well, maybe
that was a bad place to put a house/basement. (Not all lots support
basements, and not all lots are buildable.) Making interior french
drains code-required strikes me as giving designers, civil engineers,
and builders, an easy out. It may be a solution for an existing house
where you didn't know beforehand (My sister's house had them added
before they bought it), but in new construction, it screams 'cheap
shortcut'. Gotta do the homework before you build a house, including
test holes and having an engineer do a site survey, at least for the
first houses in the sub. And, of course, the lot has to be graded right.
I see sub after sub with lots as flat as dinner plates, or yards that
slope all the way to the foundation.
Maybe code should require leaving the hole open for at least one
rainstorm plus 48 hours, to see what the seepage patterns are, before
you do the foundations? :^)
Having said all that, I'm glad it worked out for you.
What exactly do you mean by 'rotting' the concrete block?
Interior french drain systems usually include a way to drain the bottom blocks
of water, if any, to redirect along with water in the trench.
If there is water in the block, that means the wall is always damp, even
when it 'feels' dry. Concrete is not waterproof- that is what you see
when that white haze (efflorescence?) shows up near leaks- the white
stuff is minerals the water leached out of the concrete and mortar,
thereby weakening it. Doing construction demo as a kid, you could always
tell walls that had been wet long-term- you could pop the bricks or
blocks apart with just a tap. It eats away at the mortar first, and then
at the concrete itself.
And when you have water exposed to the heated air of the basement, even
if hidden under the trim covering the slit trench along the wall, that
can't help but spike the humidity down there. Even when I don't have
visible leaks in summer, I have to empty the dehumidifier every 2nd day.
(Sure wish the floor drains hadn't rusted/teakettled shut...:^( ) My
sump pit has been bone-dry since I have lived here- it is surface water
coming down through the backfill and failed waterproofing, migrating
through the walls. I'm convinced replacing the outside drains (assuming
they are there at all) and redoing the waterproofing would fix the
problem, but since the basement doesn't actually flood, it would
probably be a money loser at resale time. (Trust me to buy a house right
when the 5-7 % a year appreciation in housing values stops dead in its
tracks. Value of this place is MAYBE going up at the rate of inflation.)
Interior drains beat a wet basement, but a waterproof basement envelope
is what you should strive for.
Usually is a mighty big word. And even if they are installed, a small
weep hole is more likely to clog than a 4" perf-pipe.
Another advantage [in northern climates] of keeping that groundwater
outside of your house is heat loss. The best insulation is on the
outside of your block under a waterproof membrane. Then the slab and
walls become part of your heat sink. Water running through is a
constant source of 50degree or less coolant.
if your building a brand new homew install BOTH, the trouble is most
of us own existing homes, and beyond the obvious downspot clogged a
interior french drain is the MOST effective.....
been there done all this.....
?? "big word"
I've seen what B-Dry does. And what Vulcan did on one part of my house. B-Dry
much better - decent sized weepholes in each cavity of the bottom block, very
unlikely to clog. The weepholes *drain into* the trench with the perf-pipe (of
whatever sort). Both are present.
We're talking about taking groundwater and redirecting it, from just outside the
foundation at the footer, vs. just inside the foundation. How much of a heat
sink difference do you think that is?
BTW, I agree that, at least around here in our clay-shale geology, new
construction should have *both*. But most of us like myself purchase existing
Good thing you were apparently situated to do all that yourself so I won't ask
you about labor, bringing equipment to the site, etc. (did you compare even the
costs of materials, like the gravel, so what the "snake oil" would have been??)
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