This post focuses on the next-to-last phase of the concrete work, viz., the screened porch in front of the house. Remember that you can click on any photo to enlarge it for a closer inspection.
Footings and Foundation
I over-excavated the soil next to the house to the level of the foundation footing and then sloped it downhill in order that the insulation/watershed umbrella can installed on top of the footing and sloped downhill enough to drain well. In the process, the soil under what will be the concrete floor for the 14' x 16' screened porch on the front of the house was also over-excavated. In order to compensate for the over-excavation, the footing for the porch foundation was much taller than it was wide on the downhill side which complicated forming it up for the pour.
I mimicked the forms we used for the 8" tall footings under the house foundation by using
Forms for the footings |
Poured footing; notice the bulge just beyond the corner due to a near blow-out |
I thought I had learned my lesson and made sure the forms for the short foundation wall on top of the footing would be, if anything, over-engineered. Wrong! Despite robust 2 x 4 framing for the plywood form walls, we almost had another blowout. As soon as we started the pour, a wall started bulging due to weakness of the spreaders that tie the two sides of the form together across the top. Instead of using 1 x 4s and two 6d nails on each side, I used 1 x 2s and one 16 ga 2" nails from a nail gun. We had to stop the pour while I added several 1 x 4s in the most susceptible areas and re-nailed the existing 1 x 2s with 6d nails. If I were to do it again, I would use 1 x 4s and regular nails for the spreaders throughout and 2 x 4 stakes for all of the braces because they can be driven with a sledge hammer to a greater depth than the 2 x 2 stakes that I drove with a heavy hand mallet. Fortunately, the wall did turn out to show a little less amateurism than the footing.
Poured foundation |
Backfilling
Before the slab can be poured, the backfilling must be continued until the cavity inside the footing and foundation is filled
Backfilled with sand to the height of the footing prior to installing insulation |
Insulation As Part of the Insulation/Watershed Umbrella
Over the sand, I layered mostly EPS but some XPS foam board following the
Horizontal and vertical insulation starting at the level of the top of footing |
In order to satisfy the requirements for a shallow frost-protected foundation, the porch foundation must be insulated on both sides. Inside, I merely stood EPS against the wall. For the outside, I will eventually install expanded polystyrene insulation board 2 1/2" thick supported by metal drywall track and covered with
Form for cantilevering the slab outward with rebar to support the edge |
1 1/2" over a distance of 15'.
Final backfilling, ready for 6 mil plastic and concrete pour |
After the insulation was in place, I covered it with a thin layer of sand to isolate it from the wind and to buy some time while another rainy period passed. When the weather permitted, more sand was added in lifts and each lift hand-compacted until nearly flush with the foundation wall, thus leaving space for a 5" thick slab.
Completed slab for screened porch with cantilevered edge |
Thanks for your encouraging words.
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