To support the tub and tile floor in my new master bath, my structural engineer designed a little foundation change. I have to put a footing 5 feet long under a girder in the middle of the crawl space. It completely replaces one pier and post, and comes right up to another.
So, I have to transfer the weight of the building from the original girder to a piece of W8x15 steel I-beam, then dig a trench 18″ deep by 18″ wide. These pictures show the I-beam and cribbing.
— J.S.
Look high and low to find and plug air leaks that cost you money and comfort.
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Replies
OK, after going back to change everything to short file names, here's the first attempt at a picture. If it works, you'll see the cribbing under the East end of the beam, viewed from the South.The W8x15 beam is on the North side of the original 4x6 wood girder.
Here's a closer look at the East end.
the perspective in these last two shots makes me feel better. I was worried when I saw the first pic!
Such fun, re-vamping existing foundations. I don't miss it a bit! Woe to the cook whose sauce has no sting- Chaucer
Crawling Westward along the North side of the beam, this is looking back to the Southeast at the East end cribbing. Shims between the top of the beam and the joists control which part of the span gets its load transferred to the steel. The pier in the foreground is the one that the new footing butts up against.
Here's a closer look at some of the shims between the beam and the joists, from the North. The left side needed an extra little piece of sheet steel to get the load the same.
Err, John, I dont know much about this sort of thing, but that I beam there, is that a crack from one end to the other I see???
I don't see a crack. Maybe you are looking at the rust patina along the web/flange fillets?...that's not a mistake, it's rustic
I kinda doubt there's a crack, but I'll take a real good look first thing the next time I go down there. There is a "Made in USA" stamp and some sort of batch number on the steel. Which pictures do you see the crack in?
-- J.S.
I think they were referring to the vertical line in 1660.6 (5shfrn.jpg). Looks like a pencil mark for locating the joist to me.
Ah, yes. That's a sharpie mark, roughly at the mid-point of the beam. It's a balance reference for moving and lifting the steel. I shoved the beam into the crawl space through an access hatch on the South side, and then used a C-clamp to attach the end of it to a come-along, which made it easy to drag it the rest of the way in. All I had to do was keep a piece of 2x4 under it and ahead of the balance mark to keep the front end from digging into the dirt.
Because it had to go over an existing black pipe electrical conduit, I then shoved it about 6 ft to the East of its final position, and lifted it onto temporary cribbing before pulling it Westward into place over the conduit. The idea was to always have cribbing on both sides of the balance mark. I tacked the East and middle 4x4 blocks to the side of the existing wood girder first. Then I put equal shims under the joists to be lifted, and gently but firmly pushed the beam up near the mid-point, I'd guess maybe half a ton to a ton of lift near the middle of the steel. Then I touched the shims to find any that were loose, and added to them to get them tight (I lowered the beam to get them in). Then I pushed the beam up good and snug against the joists, and put the middle C-clamp on to hold it while I built the final cribbing, and lifted and shimmed both ends to transfer the load to the steel. I lifted and shimmed until I could just barely wiggle the post to be removed by hand. The idea is to lift as little as possible to get the load transferred.
-- J.S.
I know that your engineer told you that you needed a j-bolt 1' OC, but he didn't tell you to weld up your spool did he? That is typically a no no in a structural senerio, especially when joining dissimilar metals. Rebar, most rod, and carbon steel fasteners have very different hydogen and carbon contents, and the migration of these atoms can cause problems. But that said, your probly ok, the tub won't fall down.
I was down there again this weekend doing a little final shimming adjustment and starting to dig for the footing. I checked carefully, there is definitely no crack in the steel. BTW, McMark is right about welding. In this case it's an installation convenience, and there is a little strength tradeoff for that convenience. But either way this will be way more than strong enough.
If anybody wants to see more pictures when I get the trench and form work in, let me know which old ones to delete to make room.
-- J.S.
I deleted a few pictures today to make some room.
-- J.S.
John, look at the first picture, just to the left of the pier. I doubt that it is really a crack, but it sure looks like one in the picture.
Ah, yes. It's just a scuff mark.
-- J.S.
grunt, grunt, grunt
These would go well in the photo gallery!Excellence is its own reward!
Turning to face the West, here's the first look at the West end cribbing.
Crawling still farther to the West, this is looking back to the Southeast at the cribbing and end of the beam. This shows the 4x4 block and C-clamp.
A closer look at the West end
This is looking down into the crawl space from the South side of the bearing wall. The removed pier is visible between the two joists at the bottom of the picture.
A close shot from on top showing the middle C-clamp and some shims between the beam and the joists
This is the rebar assembly for the new footing. Because it's so difficult to work in the crawl space, I pre-fabricated it and welded it together. It will slide in thru the crawl space from the access panel. Yes, the engineer did specify five J-bolts in 5 feet.
A progress report:
I've been doing a whole lot of digging and hauling dirt out in 5 gallon buckets. At last the excavation is finished. I pre-fabricated the sides of the form, and dragged them along with the rebar assembly in thru the crawl space. Then I assembled the form, lined it with 6 mil black poly, dropped the rebar in, supported by a 2x4 and the J-bolts, and finally leveled and braced it all.
It passed inspection yesterday afternoon. The inspector actually liked it a lot. Unfortunately, the pictures aren't too great. There's something about taking a picture of black poly in a dark crawl space that just doesn't work so great.
Anyhow, here's a wide shot from above, looking thru the exposed floor joists:
-- J.S.
And here's a closer look at the East end. The two scraps of 4x4 keep the rebar from swinging from side to side, as it's only supported by the 2x4 which spans the length of the form. There are two more on the other end, and they'll all be pulled out when there's enough concrete covering the bottom rows of rebar to hold it from swinging. This way the bars stay centered with no dobies. The 2x4 gets pulled when the form is full. Another sheet of ply with poly wrapped around it will serve as a ramp or chute to direct the concrete into the form.
This is kind of a confusing picture, because your mind wants to interpret the 4x4's as vertical, though they're actually leaning away from camera, with their tops against the end of the form. Again, it's the problem of taking pictures with a lot of black poly in them.
-- J.S.
-- J.S.
Hi, John-
Say, it would be even LESS confusing if you could post your pictures smaller!
:o)
Ken Hill
Here it is with the form stripped, and the notch cut out to fix my J-bolt F-up.
-- J.S.
The new cripple wall is in, the cribbing and steel I-beam are out.
-- J.S.
It looks like you only get one attachment per message now.
Here's the other picture.
-- J.S.
Interesting. I've done just enough of it to put it on the 'one of the least favorite things to do' list. One of those thankless jobs.
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-- J.S.