Detail needed: new poured fdn walls tee into existing cmu walls
Existing house with 48″ crawlspace, 8″ CMU on 8h x 16w continuous footing, will get addition. Addition will have foundation of formed and poured ‘crete, 8″ walls on footing same size as existing. What do you recommend for the structural tie of new walls to existing, where they tee into them? I thought of a couple. Mark out the junction on the existing wall, drill away and hammer out the face to expose as much core as possible. Place hooked rebar horizontally so hooks go into cores. Pour with soupy mix so ‘crete enters cavities. Drill 3/4″ holes clear through existing wall, one per block course bottom to top. Run 1/2″ long threaded rods through, with minimum 40 diameters embedment in new wall, use piece of flat steel bar as a large washer on inside of existing wall, then fix with nuts and fender washers when ‘crete is cured.
Replies
I think standard for most structural engineers would be to drill the existing and set a rebar in epoxy. Used to connect new to old concrete. I'm assuming filled cores in the existing. I wouldn't use a 'soupy' concrete, but rather vibrate it well to ensure the connection if you choose the hook style.
The issue is that the block wall is existing, and capped with a mudsill. Hollow blocks. No way to fill those hollow blocks.
A drilled hole might hit at a web, but that web is fragile enough to bust out its side with a rock drill bit going bang bang.
I can epoxy dowels all day into poured concrete solid walls. It is this hollow block thing that has me asking the q.
Epoxying some rebar into the block is sufficient.
Another approach is to carefully punch a big hole thru the top block using a small drill bit and a series of hole in a circular arrangement. Do this where the new wall intersects. Drill your rebar thru into the block, build your new wall forms, etc. Mix up a couple of sacks of concrete that are just wet enough to flow into the hole, and fill the cores, then immediately pour the wall forms and mash the wall mud into the hole to finish it off. It's really not that big a deal, if you tell the form carps to get the rods bedded in crete they will do it.
yeah, you're right. A through
yeah, you're right. A through bolt would be good. I'd avoid 'loose' poured concrete to make a connection. That's just me ... don't like wet concrete.