Brickwork

On Wednesday, November 13, 2019, I finished building new deck panels for the catch basin.  

The next task was to replace the pavers abutting the panels in such a way that I could remove the panels when necessary in order to access the basin.  I also had to ensure that the sand under those pavers will not slough off into the basin when a panel is removed.  The previous deck had a 1 by 6 plank along the north edge of the basin to retain the sand and pavers.  This was not needed on the south side, because the panels were hinged on that side.  But I decided not to use hinges on the new deck.  So I needed some kind of retention wall on both sides.  I would not use a wooden plank like I did for the original deck, because that plank rotted in less than five years.

I needed something very thin, because I didn't have much space between the new deck panels and the pavers.  And I absolutely insisted on something that would not rot.  I decided to use heavy plastic "drive down" edging from Lowe's.

The north side of the basin had vertical strips of steel angle stock firmly attached to the basin.  In the original deck, these held the board that retained the sand and pavers.  I cut sections of the plastic edging to fit between these, and drove the edging into the sand.

Mission Creep

Rebuilding the Full Size End Section 

November 8, 2019
Shortly after declaring the deck panels complete, I decided that I did not like having the end section be a single full size panel that would be very difficult to remove.  Making this a pair of half size panels, like the other sections, would result in one corner of each half size section being above the discharge pipe. I didn't know how I would handle the problem of supporting the two corners of half size panels that would be over the discharge pipe, but I thought I could come up with something.

The New End Section

Note the notch in the joist at the bottom of the picture above.  This is where the pump's discharge pipe leaves the catch basin.  New half size panels will have to have space for the discharge pipe in that same position, which means that one corner of each panel cannot be directly supported on the basin wall.  Those corners would have to somehow be cantilevered over the discharge pipe.  It was not immediately clear how to do that.  But I boldly cut the panel in half.

Now I had to figure out how to support the sides of the new half size panels where I made the cut.  Note the notches in the joists near the center top of the picture above.  The horizontal run of the discharge pipe would have to pass under the panels in this area for a length of 9.5 inches, about half way to the next joist.

November 13, 2019
I made a new transverse joist for each of the new half size panels.  To make room for the discharge pipe, I cut away the lower 2.5 inches of each new joist for 11 inches from the end, making the end of the new transverse joists match the notches in the longitudinal joists. 

This solved the problem of making room for the discharge pipe, but now last 11 inches the new transverse joists were only about an inch thick, while all other joists were 3.5 inches thick.  I suspected that this would make those joists too weak, and that they could break if a person stood near the corner of one of the new panels.

Mechanical engineers take courses called "Strength of Materials" and "Statics" which teach them how to analyze structures like this.  Unfortunately, I have never studied those subjects and cannot deal with the problem quantitatively.  I tried to compensate by overdesigning the structure.

I added a 13.5 inch length of 2 by 4 beside the thin end of each of the new transverse joists.  This would run between the last two longitudinal joists and be attached to them as well as being firmly attached to the transverse joist.  The end of this 2 by 4 would rest on the concrete wall of the basin, and therefore would be securely supported.

I was still not confident that the joist would support the weight of a person standing near the corner.  To strengthen it further, I bought two 48 inch lengths of perforated steel angle stock.

I attached them to the top edge of the new joists with 3/8 inch bolts.  Below are pictures of one of the new panels, looking from each side of the new joist.  The new joist is at the bottom of the upper picture and at the top of the lower picture.

I was concerned that the heads of the bolts would cause a gap between the two panels if they aligned.  So I positioned the bolts so that the heads of the bolts on one panel would fall between the bolts on the other panel.

Here is the end panel in place.  It weighs 52.0 pounds.  Compare to 45 pounds for the corresponding panels that don't have to provide space for the discharge pipe.

Both halves of the end section in place.

The other new half size panel weighs 50.5 pounds.  I found that I could remove and replace each of them without undue strain.


The entire deck, with the new half size end panels in place.

Now I have to figure out how to interface the deck to the pavers on each side.

New Catch Basin Panels Are Complete

Wednesday, November 6, 2019 

The new panels for the catch basin are finally complete.

There are four sections, matching the four panels of the original deck.

Original Deck

The new panels are made from synthetic wood, and the frames are Lowe's "ground contact treated" wood. They should last a lot longer than the original deck did.  They are also wider, extending over the channel covered by planks in the original deck.  This would have meant that the panels would be much heavier than the original panels, probably too heavy for me to lift.  So for each section except the one on the end away from the house, I built two panels of half the length of the originals.  Each pair of half-size panels would replace one original panel.  I could not do this for the end panel, because the discharge pipe has to pass through the frame in the middle of the panel, where transverse joists for the half-size frames would need to be.

Frames for Original Deck

So the end panel is a single full size panel.  I have to think of it as unmovable.

Frame for New End Panel

I have confirmed that I can lift the half size panels without much strain.  And the deck seems quite stable even though the panels are just sitting on the catch basin and not attached to it.

While the deck panels are complete, I still have a lot of details to work out.  What will I use to hold back the dirt when a panel is removed?  How will I support the grate?  (It is currently sitting on untreated 2 by 4's just to show how it will look.)  How will I fill in the space around the grate?  I need to do all of this in such a way that the material will not need to be replaced in a few years.