Are you required to comply with the International Building Code or the International Existing Building code? There is a 10% limit on load increases for the lateral load resisting system and a 5% trigger on the gravity system, in addition to a few other requirements (for example, a change in occupancy, or the size of the addition relative to the original building). If you exceed these, you would need to bring the existing structure up to code.
On a renovation project where we did change occupancy and we had an old stone foundation, I made an attempt to quantify the original capacity of the stone foundation. What I discovered was that even if that foundation "worked" in some locations <g class="gr_ gr_3831 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del" id="3831" data-gr-id="3831">for bearing</g>, the anchorages of structure to the foundations could not meet even minimal seismic requirements in a low-seismic zone. We even ran some specialized pull tests to check capacity and determine if we could add anchors, <g class="gr_ gr_2533 gr-alert gr_gramm gr_inline_cards gr_run_anim Punctuation only-ins replaceWithoutSep" id="2533" data-gr-id="2533">however</g> the stone foundation had zero capacity in tension. As we were planning to gut the building anyway (this review was done during schematic design), the decision was ultimately made to replace those foundations.
As far as I <g class="gr_ gr_5040 gr-alert gr_gramm gr_inline_cards gr_run_anim Punctuation only-ins replaceWithoutSep" id="5040" data-gr-id="5040">know</g> there aren't any standard "historical" structural data related to stone foundations (at least in my area, and we consulted with another engineer I would consider an expert in this area locally). In theory you could create a testing program to determine capacity, however in <g class="gr_ gr_5263 gr-alert gr_gramm gr_inline_cards gr_run_anim Punctuation only-ins replaceWithoutSep" id="5263" data-gr-id="5263">reality</g> if you are increasing loads above the threshold limits you will be required to replace them entirely.
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Stephanie Slocum P.E.
Engineers Rising LLC
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Original Message:
Sent: 03-09-2019 17:24
From: Sayed Maqsood
Subject: Stone Foundation
Hi all,
Is there any feedback in minimum design building code (ASCE 7-10) on how to retrofit concrete buildings with stone or rock foundation, or any guideline, or any important experience to be shared?
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Sayed Maqsood
Oakland CA
(510)395-4361
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