Exterior Waterproofing and House with No Footing: okay to do?

kimhojJanuary 21, 2014

I have read many of the awesome posts and posted an earlier question about interior vs exterior waterproofing, etc. Thanks everyone for your guidance!

We have finally started our exterior waterproofing project on our 1920's home in Seattle. Today was day 1 and excavation was done to the level of the basement floor, which is 7 feet below grade.

We discovered that there is no footing at the base of the house. Walls are concrete at 6 inches thick. There are no cracks or breaks in the foundation wall. The original plan was to follow the standard practice of placing the drain pipe adjacent to the footing.

Question #1: Since there is no footing, I'm assuming it is NOT a good idea to install the drain pipe (which will be placed below the level of the basement floor) adjacent to the exterior foundation wall due to risk of destabilizing the foundation wall. Any Opinions on this?

Question #2: I will talk it over with the general manager, but the revised plan calls for placing the drain pipe about 13-14 inches AWAY from the foundation wall and run a delta membrane from the wall to the drain pipe trench. Is this plan going to be as effective as the standard location of the drain pipe?

Question #3: If we proceed with plan B, then will digging a trench below the level of the foundation wall but at 13-14 inches away from the foundation wall cause any destabilization of the foundation wall?

Question #4: Would anyone recommend retrofitting footers to the foundation wall? It is a 2 story, 3000 SF house in Seattle with no visible cracks or bowing of the foundation wall.

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If there was no water problem to begin with, I wouldn't have excavated.

Now that you have, I certainly wouldn't go below the level of the foundation a mere foot away without the OK of a soils engineer.

If the engineer gives you the go ahead, shallow-trenching drains is fine. But remember those drains have to go somewhere: back into the basement sump, to daylight, or to a municipal system

Besides using a plastic membrane I would backup that protection with a spray-on elastomeric coating or cold-adhered coating or crystalline material.

    Bookmark   January 21, 2014 at 2:27PM
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Hi Worthy

we did this only because of basement water and flooding, a constant problem.
I am having an engineer come out to take a look at the foundation issues.
before they put up a delta membrane they will paint on a waterproofing coating first. Thanks again!

    Bookmark   January 21, 2014 at 2:45PM
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I wonder if there is a crushed rock or gravel footing under that wall. I've never seen a foundation wall with no footing at all.

I will be interested to find out what the engineer recommends and how you implement it.

    Bookmark   January 21, 2014 at 5:15PM
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I have exactly the same issue. How did you proceed?

    Bookmark   February 11, 2014 at 11:11PM
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The exterior waterproofing project is now done. Thanks again for all the advice.

as I stated before, our foundation walls apparently was built without any footings. however, the ground that it sits on is very, very hard.

I ended up hiring a structural engineer and we decided to retrofit 3 foot wide by 18 inch deep by 1 foot tall footings in 3 locations along the foundation wall. These were put in more to help with new structural changes and new load bearing paths down to the foundation wall.

Because of this, the trench for the footing drain was dug about 14 inches away from the foundation wall. I decided to use Grace's Bituthene 4000 waterproof membrane first, and then they applied the delta drain board. I sealed the joints were the wall met the footing with Grace's Liquid Membrane (cost me $100 for 1.5 gallons!) and Grace's Liquid mastic at the top portions of the membrane.

The drain board then came down over the footing and into the trench where the rigid 4 inch pvc pipe was placed. We then connected this to a sump pump. We also put in a floor drain/ cleanout access for the pvc pipe in case it gets clogged up.

It's amazing how much water keep trickling into the sump basin. Glad I did it. Let me know if you have any other specific questions regarding our project.

    Bookmark   February 12, 2014 at 2:46AM
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I'm so glad I can across this. Thank you so much. Did the engineer say the footing was necessary for the project or was it more of a precaution down the road? Did you put the footings below the wall or next to it. If you haven't done the footings would the drain be right against the wall? Any info on how you did the footings is much appreciated. I've been going nuts trying to get this plan in order. Thank you

    Bookmark   February 12, 2014 at 8:26AM
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Sounds good!

Only thing I wonder about:3 foot wide by 18 inch deep by 1 foot tall

    Bookmark   February 12, 2014 at 10:28AM
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The dimensions for each footing are 3 feet wide. Since the wall is itself 6 inches thick, the engineer plans dictated another 6 inches on both sides of the foundation wall, including the side of the wall underneath the floor slab. this would make the footing 18 inches deep. we had to of course dig underneath the wall and beyond another 6 inches for the footing. the height for the footing was 12 inches tall. hopefully this makes more sense.

so the footing was not just adjacent to the wall but underneath and beyond just like any normal footing would look like.

the footings were done for two reasons. One, to provide better structural integrity for the house since load bearing paths were added during prior remodels and two, to provide foundation stability for the trench drain that was being dug. Originally when we discovered the lack of footings, the plan was to dig the trench 14 inches away from the foundation. The engineer thought that was a safe plan ONLY because the soil that the foundation rests on is glacial soil and very very hard. However since I wanted to shore up the wall for reason #1,we put in the footings. My concrete contractor spent 2 days doing this and really, it was a lot simpler than I imagined.

I can post pictures of the project as well as the footings when I get back to my computer. Thanks.

    Bookmark   February 12, 2014 at 3:00PM
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My blocks are about 9 inches wide. I wonder if that does something more to provide stability over the 6 inch blocks. Ive yet to excavate from the outside. For all I know their may be a footing perhaps in certain sections. I opened up a hole in a few areas from the inside and didn't see anything. That's what Im basing this off of. So was there concern with the drain functioning properly given the distance from the foundation?

    Bookmark   February 12, 2014 at 3:24PM
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I'm not a contractor so all my advice is from a home owners perspective and experience. I have done quite a bit of research on this subject though and one of the books I would recommend is this: jack master's original basement waterproofing handbook. Here is the amazon link: http://www.amazon.com/gp/aw/d/1456405373/ref=redir_mdp_mobile

anyways I don't think you can tell if you have footings or not just based on drilling holes (bleeder holes) into your cinderblocks. the footing will be below the grade of your floor slab. IF you dig at the perimeter of the slab right adjacent to the wall AND you don't find any concrete below your slab, then you likely do not have footings. As Worthy said it is unusual for homes NOT to have any footings.

    Bookmark   February 13, 2014 at 12:00AM
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I actually opened a whole in the floor and verified there was nothing below the bottom course of block in 2 places. I suppose once I dig from the outside it's certainly possible there may be a footer in certain areas only. Do you find it as effective keeping the drain 15 inches away from the foundation? I think that's a good plan not to undermine the wall

    Bookmark   February 13, 2014 at 9:34AM
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Just read that book BTW. Good info

    Bookmark   February 13, 2014 at 3:17PM
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We've been getting a lot of rain since the drain was put in and its amazing how much water trickles into the sump basin. To sum it up, having the drain 14 inches away from the wall has worked for us even though this is a deviation from the normal design.

These recommendations are based solely on my experience- again, I am no expert in this field and would recommend either a structural engineer or a soil analysis engineer to properly answer your questions about the design of your exterior waterproofing. Good luck!

    Bookmark   February 16, 2014 at 2:09AM
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Awesome. Thanks again. I'll let you know how I make out
One last question. Where did you put the sump pump and pit?

    Bookmark   February 16, 2014 at 9:30PM
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