Foundation patch under existing mudsill
For some reason, previous owners of our house left a 2-1/2 foot gap in the perimeter foundation where a door was located. We’ve removed the door and replaced the mudsill in that area (bridging across the gap from the two adjacent sections of foundation, and now I’d like to pour a section of foundation to tie things together and keep critters from under the house. I’ve already drilled and epoxied lengths of rebar in the two adjacent sections – this will probably be more steel than most of the foundation has.
What’s the best approach to pouring a foundation that will support the mudsill? I’ve read in FHB a technique of pouring the foundation short of the mudsill, then packing mortar into the gap. With this technique, how much of a gap should I leave, and are there any magic tricks to shoving the mortar in?
Are there other approaches that are better or simpler?
Replies
Leave a 6" - 8" gap. Make a mold 5" - 7" tall for a concrete block that will fill the gap, minus 3/4 in width. Pour it when you pour the wall.
The next day, mix up some grout, sand and cement, about 3:1 by volume, and grout the block in place leaving about 3/4" gap at the top.
After a couple of hours, when the grout has set up well, mix some more grout very dry. A mass squeezed in your fist should not leave your hand wet and should break in pieces when dropped 12" into the mixing pan.
Using this drypack grout and a 1/2" x 1 1/2" stick, push some grout to the middle of the gap between block and sill. push some more in and pack it a bit, not enoughh to move, just a bit firm. Add some more and pack it a bit firmer.
By now the next bit you add can be packed real firm with your hand, maybe even hitting the mass of grout with the stick. The next layer should be able to be packed by lightly hitting the packing stick with a hammer. By the time you have a couple of inches width packed under there, you can reallllly pack it tight.
Just before filling the gap on this side completely, go underneath and really pack the gap full from the middle out, then come out and finish off the first side. Finally, add enough water to your grout to make it syrupy and with a sponge or old towel, wash the slurry across the joints between the block and the wall.
Mist the whole repair down once a day for 7 days.
SamT
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