This is a question about getting water away from the foundation wall.
We have a 1929 house in NJ, with a crawlspace under a kitchen extension out back….this is on the upper part of the grade, there is a flower garden against the house, then a patio, then a very small garden…the crawlspace foundation is clearly saturated with water, paint peeling, we have French drains inside in the basement on that side….we also have a crack on the side of the crawlspace, running down between the blocks, there is a 1/2″ gap between sill and foundation wall, so I guess there has been water/frost damage to the footing….I plan to patch the crack and put shims in the gap between sill and wall and air-seal etc…this crack btw radiates from a dryer vent put in by a previous owner, so I think there are some issues there to be investigated….
But I am getting concerned now about the underlying cause of the settlement and cracking of the foundation. Having read about hydrostatic pressure and frost heave, I am concerned about the status of this foundation long term, and am inclined to try to do something about it. There are a few problems. First, cost! Would it be possible to do this without ripping up the stone patio? There’s a flower garden a little over 3′ deep between house and patio. How big a job would this be?
I’ve read of two approaches: excavate down 1′, put down layers of bentonite that prevents water getting down into the ground (but then where does the rain water go?). Another approach is excavating down to the footing, put in drain pipe in crushed stone, backfill over it, not sure where the drain pipe would go (dig up the sidewalk around the house and run the pipe around to the below grade part? please). With the latter, I guess I’d have to rent a back-hoe to get in there, presumably in such a tight space I should let a professional do the excavation. The remaining area on that side of the house has a few feet of asphalt surface, foundation wall seems okay there (no paint peeling), okay not to install drainage there?
Then there is the question of what to do with the flower garden. Right now the garden contains hastas. Are their roots shallow enough that they can be allowed to continue to grow beside the foundation? My wife is rather upset at the idea of taking them out, not that they are so great, but there is little light there and they do at least grow albeit at a glacial rate. My wife questions why everybody says to grade the ground away from the house, since erosion ends up dumping the soil out on the patio and flattening it out….anyone have an answer for that? We also have hedges up against the front of the house (below grade side), but one battle at a time…
Thanks for any advice.
Replies
Taylor,
Gutters, down spouts, and extenders is half the first line of defense. Get as much roof water as far from the house as possible.
Sloping the landscape away from the house at 5% (6") for 10' is the other half. Keep as much ground water away from the house as you can.
Subsurface foundation drainage is the second line of protection. If any water gets near the basement/foundation walls, give it an easy path to somewhere else.
Waterproofing the foundation itself is the last "Maginot Line" and comes into play after the first two lines are overwhelmed. Its purpose is 'merely' to keep the interior of the basement dry and comfortable.
Keeping water out of the soil next to the foundation is very important to the life of the foundation.
If SWMBO wants the Hosta garden, you will need to construct a waterproof, underground flowerbox that has piped drainage to a point away from the house.
That flat stone patio 2' from the house is another point of entry for water to get into the ground too close to the foundation.
>>since erosion ends up dumping the soil out on the patio and flattening it out....anyone have an answer for that?
Erosion control . . . grass works, so do Hostas. She appears to be thinking that you only have to slope 6" over 2'. The proper way is 6" over 10', which means 8' of the patio is included. Since the patio is partially waterproof (the parts where a stone lays) you may be able to slope the 2' of garden area 1 1/4" (5%) and the 8' of sloped patio 2" (2%). Lay bentonite under the sloped part of the patio.
Here is some reading for you and your wife, Moisture in Basements: Causes and Solutions.
SamT
Edit: First you must deal with waterproofing the soil around the foundation, before you can do anything about settling and heaving issues. After fixing the cause, wait 2 full years while you monitor the foundation, then you can decide what cures the symptoms need. ST
Edited 4/24/2004 11:53 am ET by SamT
SamT, thaks for a very informative response.
Putting a slope in an existing patio does not sound like fun. I am also told that patios must be level or the stones break over time.
There is some disagreement about how seriously to take the crack in the foundation wall, and therefore how drastic to get with the countermeasures. Right now I would say the most likely scenario is an epoxy patch, a microscope slide as a marker for further widening, and ignore the water issues. A mortar or concrete patch came off during the severe winter we just had. I hope a few more years of what looks like frost heave does not do too much trouble, while this internal debate gets settled.
test
Your names not Tim, is it? (|:>)
>>Right now I would say the most likely scenario is an epoxy patch, a microscope slide as a marker for further widening, and ignore the water issues.
Have you ever taken a first aid course? The first thing they teach you in first aid is "Stop The Bleeding"
Ok. This is a first aid for basements/foundations. The first thing I will teach you is "Stop The Water."
'Nuf said.
SamT
At this point, while the patient is bleeding on the street, there is some disagreement about whether it is a scratch or a serious puncture. The argument against doing anything is the cost and the aesthetics of band-aids.
I did not realize this about patios: many people have patios up against their house. Part of patio installation is tamping down the ground to make it level. There is a clear mismatch here between the science of patios and the science of waterproofing. I've asked about this on a local BBS where patio installation is being discussed, the silence is deafening.
A friend of mine bought a house with similar problems. The bandaids have been applied, but the patient was still dieing.
I don't know what was down when. But they put a collector in the yard, but did not grade the yard. So much of the water went past the collector. Also it had a concrete patio that went upto the house and it had sunk so that it was directing water into the foundation.
They also installed an interior french drain and sump pump.
BUT the top of the foundation was pushed in over 4" and had a horizontal crack runing the length of that wall.
She had to spend 6k for vertical suport beams and expoxy sealing the cracks. Then more money to mud jack up the patio to that it directed water way from the house. graded the backyard so that rain that landed in that area would either flow into the collector or around the sides and install berm uphill of the house to direct uphill water way from it.
This the kind of problem that can get MUCH WORSE.
Depending on how much water you are getting and which way it is comming from a trench drain or collector drain system in the flower bed might be a good solution.
Yes my reading is that once the problem is bad enough, you have to underpin the collapsing footing. This involves excavating around the footing inside and out, putting an I-beam underneath, jacking up, pouring new footing in underneath, cut away the parts of the beam either side. When some of this excavation would have to be done in a crawlspace, and some would involve tearing up a pathway on the side of the house where there is cracking, $6K starts to look cheap at the price.
I agree that my best strategy may be to do something with the flower bed. First build a watertight box, or boxes, that can be drained elsewhere. If anyone has references on the construction of such flower boxes, I would be grateful. Then excavate down and put in a drain mat and pipe (where presumably water from flower box would drain). Does it seem plausible to punch a hole in the foundation wall to run the drain pipe into the sump pump that is inside for internal drainage? Then put the flower box(es) over this.
I am pretty much on my own with this. Disaster stories with pictures would help.
If anyone has references on the construction of such flower boxes, I would be grateful
The only reference I've got about this is me.
Assuming you want a foot of soil for the beds, excavate 20", slightly more where you go thru the wall with the drain.
Use a black rubber masons float and a 2:1 mix of 200 mesh silica (dust mask) and portland cement, parge the foundation. Add enough water to give it the consistany of spreadable butter. Get a kitchen spray bottle (empty Windex or similar,) mist a 2' long section, wait till all wetness is absorbed, mist another 2'. Parge and really "burn it in" on the first 2' piece untill the wall is smooth as can be. Mist the third 2' section and parge the second. Repeat down the wall til done.
Lay landscape cloth in the trench with enough slack up the foundation to cover the trench + 1' and run the rest up and out the soil side.
You have to build a retaining wall to hold back the soil because you want to use potting soil in the beds for maximum drainage.
I'ld use those red bricks with 2 holes in them, stick #3 rebar in the lowest course and thread the rest of the bricks down on the rebar. Use some more of that parging mix to pack in around the rebar in the holes. Don't grout the vertical joints 'cuz you want the soil to drain also. Oh yeah, keep the landscape cloth between the retaining / flower box wall and the soil. You can leave the top course off or use any decoration you want.
Lay your perf'ed pipe and fill with 8" drainage gravel. Take that excess landscape cloth that is going up the foundation wall and lay it over the gravel base.
Fill the whole thing with potting soil and turn it over to SWMBO.
If you stop the water, you may find that you have stopped the settling and cracking.
I'll bet a case of your favorite brew against a 6pak of bud and a bottle of Clamato that improper drainage destroys more foundations/basements than all other causes together.
SamT
SamT, thanks again for the great info, this has helped immensely.
>> I am also told that patios must be level or the stones break over time.
Flat and level are not the same thing. Stones need to lie on a flat substrate, but it can be sloped. Doesn't have to be level.