Blue Chips
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- Messages
- 632
- Location
- Maine, USA
We're building a second garage, and we are now at the point of setting up forms for the footings that will support the foundation walls. The footings will be poured directly against solid bedrock (or 'ledge' as they call it here).
The concrete contractor got started on building the forms for the footings (below) a couple of weeks ago, then had to leave for another job for about a week.
While he was away, I thought I'd do some work on the forms myself to help speed things along.
As you can see, the forms need to be scribed to fit the convolutions in the bedrock. I'm not sure yet if they'll use a concrete pump or if they can get the truck close enough to use a trough, and I'm not sure what the concrete slump factor will be, but in any case I figured that a closely scribed fit would be better than a sloppy fit.
I came up with an idea for a simple device that I thought could scribe the forms quickly and accurately. It’s probably not a new idea, but it’s new to me, as I haven’t seen one like it yet. My idea was for a device that rolls along a track attached to the form. It has a guide tube with a ball bearing at the bottom that rides up and down with the contours of the ledge and scribes a line on the form with an attached marker. I fabricated the gadget (below) mostly from scrap metal I had lying around. There are two garage door track rollers (behind the steel trolley in the photo) that follow the track that I temporarily attach to the form with a few screws. The guide tube can be inserted at either end of the trolley so that both ends of a full 8-foot board can be scribed. I can already see some improvements that I'd like to make, but for the time being, it should do the job.
The marker holder was a bit fussy. I drilled a centered hole lengthwise through a bolt (bored the hole with my lathe) and also drilled and tapped the head of the bolt for a set screw.
I sized the marker holder so that it could hold either the cylindrical metal extension of a mechanical pencil or a thick graphite lead.
The marker holder is shown below inserted into one of the threaded holes in the square tube.
The ball bearing at the bottom of the tube allows the guide tube to roll relatively smoothly over the surface of the bedrock.
Here's the track and my device mounted on a sheet of OSB. You can see the scribed line that I drew with it.
And here's the OSB after I cut the board along the scribed line. It made for a nice snug fit.
Note: The various supports, pins, rebar, etc., will be added after all of the boards are scribed and installed. A perimeter drain system will also be installed after pouring the foundation walls.
Here's another section that I cut this afternoon. It was a virtually perfect fit. I'm quite pleased with my little gadget, and I get faster at using it with each board.
The concrete contractor should be back on the job tomorrow, and I'll educate him on the use of my gadget. I think he'll like it. I hope that we can get the footing forms finished this week, or no later than the following week. After the footings are poured, a set of standard modular forms would then be set up on top of the footings for pouring the foundation wall (or ‘frost wall’ in the local vernacular).
The concrete contractor got started on building the forms for the footings (below) a couple of weeks ago, then had to leave for another job for about a week.
While he was away, I thought I'd do some work on the forms myself to help speed things along.
As you can see, the forms need to be scribed to fit the convolutions in the bedrock. I'm not sure yet if they'll use a concrete pump or if they can get the truck close enough to use a trough, and I'm not sure what the concrete slump factor will be, but in any case I figured that a closely scribed fit would be better than a sloppy fit.
I came up with an idea for a simple device that I thought could scribe the forms quickly and accurately. It’s probably not a new idea, but it’s new to me, as I haven’t seen one like it yet. My idea was for a device that rolls along a track attached to the form. It has a guide tube with a ball bearing at the bottom that rides up and down with the contours of the ledge and scribes a line on the form with an attached marker. I fabricated the gadget (below) mostly from scrap metal I had lying around. There are two garage door track rollers (behind the steel trolley in the photo) that follow the track that I temporarily attach to the form with a few screws. The guide tube can be inserted at either end of the trolley so that both ends of a full 8-foot board can be scribed. I can already see some improvements that I'd like to make, but for the time being, it should do the job.
The marker holder was a bit fussy. I drilled a centered hole lengthwise through a bolt (bored the hole with my lathe) and also drilled and tapped the head of the bolt for a set screw.
I sized the marker holder so that it could hold either the cylindrical metal extension of a mechanical pencil or a thick graphite lead.
The marker holder is shown below inserted into one of the threaded holes in the square tube.
The ball bearing at the bottom of the tube allows the guide tube to roll relatively smoothly over the surface of the bedrock.
Here's the track and my device mounted on a sheet of OSB. You can see the scribed line that I drew with it.
And here's the OSB after I cut the board along the scribed line. It made for a nice snug fit.
Note: The various supports, pins, rebar, etc., will be added after all of the boards are scribed and installed. A perimeter drain system will also be installed after pouring the foundation walls.
Here's another section that I cut this afternoon. It was a virtually perfect fit. I'm quite pleased with my little gadget, and I get faster at using it with each board.
The concrete contractor should be back on the job tomorrow, and I'll educate him on the use of my gadget. I think he'll like it. I hope that we can get the footing forms finished this week, or no later than the following week. After the footings are poured, a set of standard modular forms would then be set up on top of the footings for pouring the foundation wall (or ‘frost wall’ in the local vernacular).
£46 in the bin. Another one ordered...
