Need advice from the Concrete Cognoscenti...Foundation work and leaks

To set the scene. When I built my shop, I had to remove the back of my existing attached garage so that I could drive through; no room at the side.

The original foundation was as high as the parged bit that you can see in the picture. (Where the brick starts) About where the chair is, there was a setof stairs going down into the basement. Keep that in mind because its part of the problem. When removing the back wall, the contractor sledge hammered the foundation wall to about 8 inches below grade and poured a new slab on top.

Ever since I build the shop, I get a bit of water in the basement when it rains really hard or if snow builds up around the back of the house. Especially around the drain spout. I have been treating it like a run-off problem and that has helped, but not cured the issue.

The other day, the question of how the old foundation was tied into the new slap pops into my mind. So I grab a shovel and decide to have a look. Well, shovel did not help cause they poured a subteranean apron about 8 inches past the slab that I had to cut off so I could find the inerface. I gotta say I am not impressed.

Pretty much like that long the whole interface. Im sure its sealing in some places and I am sure it is NOT sealing in other places. This also explains another mystery: When I do get water in the house, it keeps seeping well past the rainy day. Almost like the burried stairwell (full of who knows what kind of loose fill?) is getting full of water and slowly draining in to the basement.

So, needles to say, my concrete knowledge is zippo. The knee-jerk reaction is to build some kind of damm in front of the whole lot and pour up to grade hoping that it will seal off the ugly interface. How to prepare the existing foundation wall, clean out the crack and any other subtle details like what flavour of concrete to use is non-existent.

Advice welcome.

Looks like a good place to include some kind of a drain (french or other) in the repair. Tie in that a downspout too?

Is that a drain around the corner to the right? (must be lower than that seam)

If you drain the water at a level below the seam it should follow the path of least resistance to the drain?

If you can get access to the cold joint (inside or out) you could inject urethane into the joint. I'm not sure if any diy kits are available but if you can find a contractor in your area that does it, it shouldn't be more than a couple hundred bucks. Then do everything you can to keep water from reaching that area. French drain would work, keep soil off of the concrete any way you can. Hydro guard membrane or a butyl rubber membrane complemented with plenty of drainage would be your best bet.

The contractor should have used something in the cold joint when they poured the new concrete. I liked to flange in the old concrete and use a material that expands when wet, I can't think of the name right now but it's irrelevant as it wasn't used when the work was done. Below grade cold joints are a bad idea without lots of drainage and a water management system to deal with it.

You need drain tile. Water is lazy just like electricity. It'll take the path of least resistance. Dig out 2-3 feet down and around the corner about 2 feet away from the house. Put a foot of #6 stone on the bottom. Put the drain tile tube in there. If you have a downspout, connect it to the tile with a T. Bury it with #6 stone. Send the end down and away from the house in a trench and let it exit out on the lawn.

I assume the lot pitches away from the house?

Appleseed wrote: You need drain tile. Water is lazy just like electricity. It'll take the path of least resistance. Dig out 2-3 feet down and around the corner about 2 feet away from the house. Put a foot of #6 stone on the bottom. Put the drain tile tube in there. If you have a downspout, connect it to the tile with a T. Bury it with #6 stone. Send the end down and away from the house in a trench and let it exit out on the lawn. I assume the lot pitches away from the house?

What kept me thinking this was a drainage issue for all these years is the fact that the lot has like a total of 3" of elevation change from front gutter to the back of the lot. Its like a pancake.

there is a downspout right around the corner. Thing is that until this week-end I was not sure this was not a weeping tile issue in the first place. Almost 60 year old clay weeping time is not to be trusted. In order to test it, I have kept the excavated bit flooded for most of the week-end and no water in the basement.

My reluctance to tie in to the downspout right around the corner is that you can see I already repaired the clay pipe down-pipe with an ABS section...afraid that if I revisit I will be digging another hole down to the weeping tiles.

What I need here is a concrete version of the MIG welder.

What I think I am going to do is power wash the crack and use a caulk gun dispensed product of some sort.

Your best bet is a membrane waterproofing system over the joint. This will have an asphalt-like adhesive primer that you coat the wall with, then a membrane that you adhere over the joint. Then you cover that with rigid insulation board to protect it. Also look into a product called Aquaflash, which may be rated for below grade application, too.

In reply to NOHOME:

I wouldn't. Epoxy injection is often described as welding concrete. However you don't need epoxy, you need urethane injection. It is designed to do exactly what you are looking for. You inject, under pressure, a hydrophobic urethane liquid that expands in the neighborhood of 400% it's volume. You can and will fill the void completely with a product designed specifically to do what you need it to. I've injected urethane into cracks as small as 1/32" and as big as 3/4" with excellent results. If you don't want to find and pay someone who can do it then you'll need to do a membrane/French drain approach. If the yard if flat you can always drain it into a catch basin and pump it to the curb, or another suitable location where it won't circulate back or flood a neighbor.

What you are looking for is out there. Don't cheap out and put a caulk on it only to have continued problems in perpetuity.

A French drain is helpful for small amounts of water in soil that percolates well, but water ultimately needs someplace to go after the soil is saturated. If your lot lacks an easy path to drain away by gravity, you need to waterproof that exposed slab edge - especially the cold joints where newer concrete meets the old foundation wall.

Since the exposed (below grade) concrete surface looks like hammered dog E36 M3, it would help to bush hammer or grind it so it's less irregular.

There are cemetitious waterproofing products and elastomerics. I'd try something like Thoroseal first (a brush-on cemetitious waterproofing). Note: BASF bought Thoro and now it has a new name, but I believe you can find cemetitious waterproofing at big box home stores.

If you've found a crackthat obviously creates a path for water intrusion, some chipping + This stuff will stop it.

In reply to OHSCrifle:

Ooh, I forgot about xypex. That's some pretty cool stuff. The more water it's exposed to the more dense it gets, tiny crystals grow. Really cool stuff. We used it once on a project that had badly honeycombed poured concrete walls that were continually damp. Pretty expensive if I remember correctly.

Nick (Bo) Comstock wrote: If you can get access to the cold joint (inside or out) you could inject urethane into the joint. I'm not sure if any diy kits are available but if you can find a contractor in your area that does it, it shouldn't be more than a couple hundred bucks. Then do everything you can to keep water from reaching that area. French drain would work, keep soil off of the concrete any way you can. Hydro guard membrane or a butyl rubber membrane complemented with plenty of drainage would be your best bet. The contractor should have used something in the cold joint when they poured the new concrete. I liked to flange in the old concrete and use a material that expands when wet, I can't think of the name right now but it's irrelevant as it wasn't used when the work was done. Below grade cold joints are a bad idea without lots of drainage and a water management system to deal with it.

This advice is great.

(bentonite is probably the swelling stuff that wasn't used in this joint)

Nick (Bo) Comstock wrote: In reply to OHSCrifle: Ooh, I forgot about xypex. That's some pretty cool stuff. The more water it's exposed to the more dense it gets, tiny crystals grow. Really cool stuff. We used it once on a project that had badly honeycombed poured concrete walls that were continually damp. Pretty expensive if I remember correctly.

I had an elevator pit in a parking deck located 40' below the water table fixed by a topical paste made from Xypex, on the Inside of the pit walls. It was a last ditch effort that worked. I'm pretty certain that it is not cheap.

You can get diy urethane foam injection kits. It expands rapidly but nondestructively when exposed to water. I had rain water leaking in around my water service entrance and I used a kit of that stuff and it worked great. It's a closed cell foam when cured so it's waterproof. You could inject it all along that crack and then once cured you could flash it with an adhesive membrane.

To make the hammered dogE36 M3 more flat you could use a 9" grinder with a diamond grinding wheel on it. I rented a grinder and bought the wheel to make a section of concrete flat and it moved quickly. Just wear long sleeves and safety glasses or a full face shield because you're gonna get pelted with bits of concrete. I think the diamond wheel was $50 and the rental grinder was $40 at Home Depot.

To get you started researching, search google for "polyurethane foam injection kit"

I think I used this stuff:

https://www.amazon.com/Mar-flex-Concrete-Crack-Repair-POLYURETHANE/dp/B006WCL59K

But I'm not sure. Note it's rated for how long of a crack it can seal. And doing the grinding first would make your job easier because you have to epoxy injection ports every so often over the crack then use the epoxy like a grout over the entire length of the crack to keep the foam from spilling out of the surface of the crack.

I strongly recommend flashing over it before backfilling since its exposed anyway. I think that will really help.

In reply to dculberson:

Cool, they are selling DIY kits now. Sweet. I've used Mar-Flex products in the past, just not their urethane or epoxies.

It turns out Emecole, the company that supplied our epoxies and urethane now sell DIY kits as well. Over a period of ten years I used there products with great results from residential to massive commercial projects. Lou Cole the chemist and part owner of the company was great to work with and would tweak his formulas for us on specific projects. It probably goes without saying but I can personally recommend their product. http://www.emecole.com/10-ft-foundation-crack-repair-kit-polyurethane-foam-diy.html