Twist and pour

Yes, I wish this post was about drinking beer… May be a beer would have helped!

This was the day of the porch footings concrete pour – a busy day. I started out by lining the form work with a 6 mil polyethylene sheet. It should act like a damp proof, minimizing the potential for soil moisture rising up into the footings and ultimately the foundation wall.

Next I put back the horizontal rebar I had laid out the day before. To tie the future foundation wall to the footing, I had a 48 L-shaped rebar section. I attached the 12 inch horizontal leg (the short leg) to the already placed rebar, with the 18 inch leg (the long leg) rising vertically from the footings.

These vertical legs need to lign up with the center of the future foundation wall. But keeping them in line and vertical proved to be rather challenging, and we ended up constantly adjusting them during and right after the concrete pour.

I had rented a concrete vibrator to make sure the concrete would flow nicely, fill all the nooks and crevices, and to remove air bubbles or air pockets. We screened the top of the footing to make sure it was level and finished the job by troweling a key along the vertical rebar legs. The key will help with the mechanical connection between the foundation wall and footing.

The twist

The process wasn’t nearly as smooth as it may appear in the above narrative or time lapse.

My problems started with the concrete truck arriving slightly early with me not being quite ready. Plus the truck was huge – or to be more precise – very long. We had an excellent driver and he made it into the narrow alley. But swivelling the truck into the back yard eluded us, despite trying for a good 30 minutes.

We finally had to dig out the fence post next to the gate, which gave us an opening large enough for the truck to make it into the yard and back up to the job site. We were ready to pour, when I twisted my ankle – and I twisted it good!

I had to sit down for a minute to contemplate my options, of which there was really only one: A $1,000 mass of concrete sitting in a truck that needed to be poured. So I got back up on my legs and started limping around as best as I could.

Our neighbor William saved the day by taking over the heavy lifting and basically running the show. I would have been in dire straights without him.

Thank God I didn’t untie my boot when I twisted my ankle! Once I did at the end of the job, there wasn’t even any limping around anymore. Cathy hauled me to the emergency room where I learned that it was a bad sprain and that I’d earned at least two weeks of forced vacation.

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That footing will be tied to fond memories forever!

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Getting hooked on an ancient gadget

The basic footing preparations were done, so I could shift my focus to the details.

I had a little more excavating to do, in order to match the footings to the layout and elevations. At this point I opted for some additional resilience. The architectural details specified a two foot wide and one foot deep reinforced concrete footing. Some number crunching convinced me that the incremental cost of increasing the footing width from two to 2 ½ feet would be worthwhile. Plus, we had the room to add three inches to each side.

Our salvaged porch lumber came in handy. I used the old two by eights and two by fours to build the formwork for the concrete.

This was the moment where precision was not an option but an absolute necessity. The top of the formwork had to be perfectly level since we still have to pour the foundation wall onto the footing. It is a b***h of a task and a huge time suck to build the wall formwork on an uneven footing. So, starting with a perfectly level footing is the way to go.

But how do you do that? Using a spirit level is risky. Its a handy tool, but not precise enough, certainly not over the distance of 42 feet (the total length of the footing). Modern technology has given us the gift of laser levels. But I didn’t have one.

This is where my apprenticeship in the German landscape industry came in handy. I remembered that before the days of laser levels, we used something called “Schlauchwaage” – which translates into hose or water level. And if this nifty gadget was good enough to for the Egyptians to set and check the elevation of the Pyramid footings, it will be good enough for our porch footing.

There are several variations of water levels. I simply used 50 feet of clear vinyl tubing which I filled with water. There cannot be any air bubbles in the water, or they would distort the hydrostatic pressure and render incorrect readings.

Because the water in the tube seeks a hydrostatic equilibrium, the water level at one end of the tube is equal to the water level at the opposing end.

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This gave me an extremely simple yet precise tool to transcribe the exact same elevation across the entire formwork length. You could even use the water level around corners or across different rooms. There’s no need to have a visual connection between the two tube ends.

But beware of the meniscus, particularly in smaller tubing! The surface tension tends to create a concave or convex water surface, which, if looking at it from the right angle, can lead to 1/8 or ¼ inch inaccuracies in readings.

All right, enough gadget talk. The much less precise yet essential rebar layout required my attention. This got me a lot closer to pouring the concrete, which was scheduled for the next day.

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Footing, drains and sewer

My small and manageable task list started multiplying as I got closer to pouring the new porch footings:

  1. The concrete apron which I left as a rain screen was ready to be cut back a foot. That gave us more freedom of movement.
  2. I had removed the foundation wall. It was know time to remove the remaining limestones from the footing.
    With that done, I was able to set the rough layout and elevation of the new footing.
  3. Knowing the extent of the new footing allowed me to extend the footing drains far enough out to the outside of the future footing, and equally
  4. extend the storm sewer and fit it with a clean out tee.

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Excavating for porch footings

It has been a few months since I last tested my grave digger skills, and I am due for a refresher.

The old limestone foundation wall was pretty wide. Yet, it wasn’t wide enough to give me the room I needed for the new footings I had to pour, or the footing drains I needed to install.

What other option was there than to put some effort into excavating?

I left the existing concrete pavement in place. It acted as a rain screen and prevented us from treading the soil edge loose and having it fall back into the hole.

We stored half of the soil on our vacant lot, and the other half on our neighbor’s lot. We are very lucky with our neighbor! He saved us a lot of time. His graciousness allowed us to move any soil only as far as absolutely necessary.

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Limestone unlimited

I was about to enter salvaging heaven!

The porch tear down only generated a limited amount of salvaged lumber, and we recycled the concrete foundation. The old limestone foundation, however, was something I have been salivating over for a while.

There was not a stone to be wasted here! This is priceless garden material. But we first had to disassemble it stone by stone.

Well, the excitement about the limestone was a little muted once we started with the demolition. The material was a lower quality than that of the building foundation. A lot of the larger stones separated along the sediment lines into smaller, thinner slabs. This was particularly prevalent at the location of the old downspout where the hydrostatic pressure had built up.

We found the biggest and best quality stones in the two corners. It was at times a challenge to lift them out of the pit. All of the salvaged stones, large and small, are now waiting for their new garden assignment.

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Cracking concrete until the foundation falls

Our old back porch was special in many ways — just not in a positive way. For instance, it had two foundations. One was an old limestone foundation wall (more on that later), and the other was a reinforced concrete foundation in front of it.

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The concrete foundation was added sometime in the past 10 to 15 years to stabilize the limestone foundation behind it, which had started to buckle inwards. And this demonstrates the power of water and the importance of properly working drainage.

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The buckle in the limestone foundation had its apex where the downspout met the sewer pipe. At one point that sewer pipe must have been cracked or broken, and probably blocked, behind the limestone foundation. Water rushing down the downspout didn’t drain but rather started saturating the soil behind the limestone foundation. The frequent hydrostatic pressure started to push the foundation inwards.

I could tell that the broken sewer tile had been replaced and the concrete wall poured to tame the buckle.

Our job for the day was to remove the concrete foundation.

There wasn’t much to salvage or recycle from the old porch. The concrete, however, is a sought after commodity. There are recycling stations that take it and process it into recycled aggregate.

Similar to the basement floor, I may end up getting part of my own concrete back when I install the recycled aggregate base for the new concrete floor under the new porch.

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Back porch tear down

I had scheduled the removal of that eyesore that was attached to the back of our building – our old back porch – back in late March. We had to wait for the snow to clear but finally proceeded with the cosmetic surgery.

The surgeon’s tools of choice: Crow bars, sawzall, large scrapers and sledge hammers.

Revealing

It got interesting from the get go!

The first job was to separate the porch roof from the main roof. The crew cut through the existing roofing and began to scrape it off.

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We knew the porch was in bad shape and not safe. But I now got to see what “not safe” meant, as the decking along the porch edge was partially rotten. That’s the kind of skylight you don’t want!

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Looking at the cross section of the roofing threw me back to the deconstruction days of our deep energy retrofit, when I felt like I was conducting an archaeological dig, peeling back the construction layer by layer.

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We have an impressive 2 ½ inches of very old, pretty old, not so old, and newer roofing on our building. One layer after another. Can you imaging the weight of this? If I assume 90 pound roll roofing at ?” per layer, we have a least 18 pounds of roofing per square foot. That is about ¾ the weight of an extensive green roof!

Destruction

One and a half days, and our eyesore was gone, including the clean up.

Why is it so much fun to watch this planned destruction? It was fun watching it while it was in process, and I still have a blast revisiting the time lapse. Or even just this little video of the west wall coming down.

Waste reduction?

I spent some time walking through the old porch, looking for items that could be salvaged, reused, repurposed, recycled or otherwise diverted from the landfill. Because pretty much everything was painted, the majority of the porch was in a non-recyclable state. I managed to pull out a handfull of items, such as a door and some two by fours, along with a number of floor joists and some nice posts. I’ll either find a use for them or see if I can find a taker, despite the paint on the lumber.

The one thing that surprised me is that our contractor fit the whole porch into two trailers, with which he hauled it off site. I would have ordered a big dumpster, and it would only have been half full.

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Saying goodby…

We had a false start on our back porch project late last year, and I used the winter months to get it back on track.

It was time to say goodby! Goodby to our old, ugly, shaggy, and crumbling back porch. This was an easy goodby…

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Back in late March, we were waiting for the weather to break and for the demolition crew to move in.

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Do-over dilemma

Project specific factors usually determine what insulation method would be suitable. For our roof those factors were a target R-value of 60 or more, the existing low slope roof with its ten inch roof joists, the spatial constraints of the south attic, and the need for some roof deck repair down the road.

We reconciled these sometimes conflicting factors with an insulation assembly that started with three layers (total of 10 1/2 inches) of rock wool batts (R-45), followed by four inches of XPS foam boards (R-20). That should give us an R-value of 65 anywhere between the roof joists.

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It looked like we had the perfect roof insulation for our project. Yet, it was also risky, which suddenly made it a lot less perfect.

What I neglected to consider in my schedule and material driven decision making, was the building science – the issue of moisture management.

From cold to wet to rotten

The current insulation assembly is so effective that I created a cold roof deck. During winter time, its temperature will be close to the outside air temperature. In other words, it will be around or below freezing.

Any water vapor in the assembly is likely to condense at the cold roof deck – or, to be more precise, the water vapor will be absorbed by the boards and the upper (cooler) sections of the roof joists.

That could drive up the material moisture content. Once the moisture content rises above 28%, rot or biodegredation may set in. This could compromise the structural integrity of the roof deck and roof joists.

See also: BA-1308: Moisture Control for Dense-Packed Roof Assemblies in Cold Climates: Final Measure Guideline

We did fairly successfully airseal the 2nd floor, including the roof plane. That is, however no guarantee that the roof assembly is vapor tight. Plus the stack effect will constantly pound the insulation assembly with warm and moist air. Some of it will get into assembly. But I am not sure if it has an effective way to get out again.

The accumulation of moisture in the assembly would probably be a slow and gradual process. To get to and sustain a risky moisture content would probably take years. So should I lose sleep over it?

Yes. And I already lost a lot of sleep over it! We plan to be in this building for many years to come. The aspect of durability is very important to us. It makes economic sense and is sustainable. Plus we plan to put us a green roof. I don’t want to ignore the problem now only to risk costly structural roof issues 5, 10 or 15 years down the road.

The fix

Our current insulation assembly is upside down. If I move the XPS insulation on top of the roof deck, I should be able to keep it warm enough to reduce the sorption risk (often referred to as condensation).

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The rock wool insulation can stay in place as is. It is vapor open and allows for seasonal drying of the now much warmer roof structure. With that, the moisture content of the roof deck and roof joists should remain in the safe zone, which would be below 20%. (Mold growth is likely to occur if the moisture content is in excess of 20%)

I don’t like doing things twice. But in this case it is the lesser evil. I will now spend a few days taking down our carefully installed XPS insulation. Reinstalling it atop the roof deck will happen sometimes down the road.

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Trying to determine how to insulate or ventilate a roof isn’t easy. Here is a list of articles that guided me in the process:

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Sprouting joy!

At the beginning of last winter, I invested some time in seeding native sedges. For the plant geeks among you, the two species of my choice were Carex sprengelii and Carex vulpinoidea.

My intent was to grow enough of them to start turning our parkway, which is currently covered in turf, into a rain garden with an ornamental yet reasonably rough and tumble selection of native prairie species.

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Getting some native species to germinate is not easy. But throwing my research and horticultural background into the mix, reading up on the science, plus trial and error led me to a reasonably successful method: Potting soil plus sand bedding plus stone chip mulch.

Timing is also critical. Seeding the sedges at the onset of winter puts nature to work. The frigid winter months allow the seeds to imbibe (slowly absorb moisture) and they get cold stratified. This should ultimately break the seed dormancy, and lead to a reasonably successful germination rate.

Does it?

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I started peeking into my trays and noticed a tender green fuzz emerging! Success! I just hope that enough of the pots will produce sedges so that I have enough material to plant out the parkway.

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