The Basement: Foundation

We have to do major structural work to support the changes we are making to the house.

Just like most of the houses in the neighborhood, the foundation was poured a long time ago. It was built to the norms of the times. Which is to say, it is unreinforced Portland Cement mixed with rocks from our fine river. There are no footings to support the concrete foundation walls. This means that the wall is sitting on top of some dirt, rather than on top of something built to provide stability and resist sinking.

Here’s a look at the Going Queen’s foundation after some nice people took a concrete saw to it:

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Why are there no footings holding up the foundation? Because they weren’t typical in homes built in the early 1900’s and before. At least that is what people keep telling me. However, the concept of a footing seemed so simple and obvious that I looked into the history of foundations and construction techniques. Guess what? The Pueblo Indians used footings. The Egyptians used footings. The ancient Greeks load down some nice footings.

However, the ancient Concordians from 1907 chose to forgo footings so here we are.

While working with our architect and engineer, they explained that if we were to leave all the interior walls as they are, make no exterior modifications, not finish the basement, and not add or modify any window openings, then we could leave the basement alone.

But where’s the fun of that?

If we were to change even one of those things, it would require that we recalculate the effect on vertical and horizontal loads and the results of that analysis would trigger work on the foundation.

Since we were making many of these types of changes, it was clear we had to do the structural work.

Here are the changes we are making to the house above that have the biggest impact on the foundation below:

  • Adding or enlarging window openings

  • Removing interior structural support walls

  • Relocating a staircase

  • Adding egress windows in the basement walls

We considered several options for updating the foundation:

  • Use Foundation Piers to retro-fit the existing basement with a structural footing.

  • Demolish the Old Basement and Build a New Basement

  • Rebuild the Foundation and Basement In-Place

We went with the last option. But, since I have until August 5th of 2018, I’ll describe each of them to you anyway.


Foundation Piers

Foundation Piers are big screws you drive deep into the ground, at an angle, so they get under your existing foundation and then you install a bracket on top of them that your existing foundation sits on.

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We evaluated these because they are inexpensive versus other options but still do a good job of adding structural support. However it became apparent these weren’t a viable solution for us. They can work well if your existing foundation is in good condition, especially if the concrete used to build it was reinforced with steel. But if your foundation walls are not reinforced, while this solution will provide a solid footing, it still won’t let you alter the existing foundation walls or properly tie down the house to them. In our case, to finish the basement, we would need to add larger windows for emergency egress. This would mean cutting into the old, unreinforced walls, which would likely compromise them making the new Foundation Piers meaningless. In addition to that problem, we’d be required to bolt the house to the foundation. If your house was built before 1980, then it’s probably just sitting on the foundation rather than being actually attached to it. If you are renovating it, you’ll probably be required to bolt it down to bring it up to modern standards. This means you need to sink concrete anchors into the walls. Well, going back to the fact that the Going Queen’s basement walls are unreinforced cement and river rock, if you tried to bore a hold and put an expander in the wall so you’d have something to tie into, you might burst the wall or cause it to crumble.

So, just going with Foundation Piers didn’t make sense for us.

Building a New Basement

You can imagine how this is done. You just simply jack your house way up into the air, hold it up there without dropping it on anyone, and jackhammer out the existing basement, remove all the debris, and make a new one.

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I just couldn’t get behind this method. It seemed expensive. It also seemed risky. The upside to this method is you get a brand new foundation and basement that is built to modern constructions and seismic standards. The downside is that it’s going to fall over while you are doing it.

Rebuild The Foundation and Basement In-Place

This is what we are doing. The upside to this method is that it cost less than a full rebuild and you still get a structurally sound foundation and basement but without the lifting it into air part. The downside to this method is that you lose some interior volume in your basement.

Another potential downside is that I’m not sure it really cost less. There is actually a lot of additional work when you build a basement incrementally.

This method involves:

  • Cutting out the existing basement floor

  • Digging underneath the existing concrete walls

  • Pouring new footings around the perimeter of the home

  • Building new reinforced basement walls, inside the existing walls, and on top of the new footing

  • Pouring a new basement floor

To illustrate this, I can use pictures from the Going Queen because that’s whats going on under the house right now.

The trick is that you have to do the work in segments. The old basement is still doing it’s job of holding the house up. You can’t just tear out the floor and dig under the existing walls because when you are done digging there is mostly air in the hole.

So, you remove the basement floor in alternating segments. You can see in the basement design below where the engineer has identified the first round of segments to remove. The gray areas below are to be cut out, dug and poured first.

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It looks so clean and clear in the drawings. Here’s what it looks like in real life…

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Before they started digging, the basement crew put up temporary supports around the hole to transfer the weight of the structure off that segment.

Because of the confined space, all the work is done by hand and the material is removed from the basement, bucket by bucket.

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Concrete in general is challenging labor, but this basement construction method is exceptionally hard work.

In 1989, I’d just come home from the army. I’d been overseas for a couple years fighting communists and keeping the world safe for democracy by drinking a lot and marching around and cleaning things. On my return, I needed a job so I took a position on a construction crew working in downtown Los Angeles with a concrete contractor.

I worked on a crew of mainly hispanic tradesmen. They were skilled and indefatigable. I was not skilled and easily fatigued. Some of these guys were in their fifties. I couldn’t keep up with any of them and it was embarrassing to be me. I tried to tie rebar together as fast as my crew-mates, build forms as well as they could, and swing a sledge hammer for as long as they would in the 100+ degree heat of an LA summer. They were not impressed with me. I slowed them down and they had to carry me. Litterally. I actually passed out from heat exhaustion while pouring the foundation for a California Pizza Kitchen restaurant and the guys had to carry the my delicate frame into the shade. I got voted off the island.

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I have a healthy respect for how difficult it is to work with concrete.

After the holes in the floor are excavated, steel rebar is added to reinforce the footings and basement walls. Looking down into one of these excavated squares, you can see the new reinforced footing taking shape. The steel rebar is pushed into the dirt in the adjacent sections so that later, when that section is dug out, the rebar is already there and connects the footings together.

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From our plans, you can see a cross section of what’s happening. The gray area is the old wall. You can see how the dirt is dug out under the old wall and down in an “L” shape to form the footing.

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After the rebar is tied, forms are built around the rebar structure to create the desired dimensions for the new wall and footing. You can see below how the new all is built right up against the old one. The new walls 6” thick.

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The form is supported with bracing to hold it in place.

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The forms have to be further secured because once the concrete is pumped in, the frames get very heavy.

On December 14th, a concrete truck showed up at the Going Queen and pumped 21 yards of concrete into her basement. A ‘yard’ is the standard measurement for aggregate material in those countries that use the ‘Imperial System’.

Refer to the map below for the nations that use this superior system of measurement.

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The United States is not the only former British colony still using the system of our prior overlords, who they themselves have abandoned.

The United States, Liberia and Myanmar have a lot in common!

It makes a lot of sense to stay on the Imperial System of Measurement rather than migrating to what the rest of earth uses. What’s the worst that could happen?

Obviously what I’m trying to say is that 27 cubic feel of concrete and a yard of concrete weighs about two tons which is to say that they pumped 84,000 pounds of concrete into the basement on December 14th.

To prevent the forms from being blown off the walls from all that weight, they added braces that were secured to the joists and anything else they could nail into.

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Once the concrete dries, the forms are pulled off and now we have some new reinforced wall segments.

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On the top of the walls, foundation bolts are embedded into the concrete. These will be used to tie the house down once they complete the transfer of the load to the new foundation wall.

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On the sides of the new walls, tubes were embedded in the frame so once the frame is removed, rebar can be pushed into the hole to tie it to the next wall they will build right up against it.

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The concrete is cut out between the newly poured segments.

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Temporary headers are installed to bridge the gab between the newly poured walls so the beans and floor joists over the segments they area about to dig are supported.

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The area is excavated again down to the where the footings will be poured.

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Once this is dug out, you can see the rebar sticking out of the new footings on either side of the excavated hole. These will be tied to the footing and wall they are now building between the new wall segments.

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The center of the basement was also cut, excavated, reinforced and poured. This footing runs down the middle of the basement long-ways and will carry the weigh to the center beam and posts that will carry a lot of the interior weight of the house.

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Jenny pushed me into this hole to see how deep it was.

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The finished basement floor will be about two imperial feet lower when we are done. But we’ll have to come back to this later. Once they get the walls poured, they’ll move on to other parts of the project for a while. Eventually, they’ll come back and rip out the remaining basement floor, dig the rest of it down and pour a new floor. I think the plan is to come through the back corner with a small excavator and this part with a machine.

Why are we lowering the floor? We’ll cover that in the entry on ‘murder-proofing’ the basement which is next, or maybe next after next.

More Stuff:

Residential Seismic Strengthening