New foundation overlaps to an existing foundation
New foundation overlaps to an existing foundation
(OP)
Hi,
The strip foundation of my new structure overlies in the foundation of an existing strip foundation. I attached a file of my propose detail design.
I would like to ask for a second opinion for my design proposal. Any reference books I could refer to regarding connection of new foundation to existing foundation?
The strip foundation of my new structure overlies in the foundation of an existing strip foundation. I attached a file of my propose detail design.
I would like to ask for a second opinion for my design proposal. Any reference books I could refer to regarding connection of new foundation to existing foundation?





RE: New foundation overlaps to an existing foundation
I would much rather see the new column footing underpinning the existing strip footing as much as possible to minimize the eccentricity to the new footing.
Mike McCann
MMC Engineering
RE: New foundation overlaps to an existing foundation
You have a 700 x 400 column, which indicates a substantial load, and yet you have little continuity in the bottom reinforcement of the footing. Do you even know how that existing footing is reinforced?
In summary, I think your detail is terrible. Your new footing needs to be new. If you can't move the column over far enough to avoid the existing, then as Mike said, you need to underpin.
RE: New foundation overlaps to an existing foundation
The exception: In a similar condition, I ran the footing back into the new building to pick up the first interior column, making it as two column foundation, and cantilevered over the existing footing. I placed a compressible material between the old and the new. It was cheaper than underpinning in my case.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: New foundation overlaps to an existing foundation
hookie: I know the reinforcement of the existing foundation base on the As-built drawing of the client.
As hookie said, my concern is the continuity of the new footing to the existing foundation. I have read one article in an engineering web site which I think answered my concern.
"........The intend of the dowels are to pull together the old and new concrete together such that their bonding become inseparable. Some engineers require the edges of the existing footings and foundations where the new and old concrete meet be roughened. Even some require application of bonding agent to enhance the bonding.
Since most footings and foundations are coated with waterproofing, the waterproofing must be removed and scraped clean to allow concrete to concrete bonding. Failure to do this will yield weak connection and can lead to water leakage.
The longer side of the dowel also call the lap splice, is calculated by multiplying the bar diameter in inches by 40. For #4 bars, it requires 20 inches long lab splice.
During the pour make sure these connection points are vibrated really well to make sure there are no honeycomb or exposed reinforcements."
RE: New foundation overlaps to an existing foundation
RE: New foundation overlaps to an existing foundation
RE: New foundation overlaps to an existing foundation
RE: New foundation overlaps to an existing foundation