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Extensions to small buildings

Extensions to small buildings

Extensions to small buildings

(OP)
When extending a building,  say a two storey dwelling, should the new members (beams, columns footings)be 1. joined to the existing members by dowelling or exposing rebar splicing new rebar and concreting or 2. not be connected at all, allowed to act as separate structure all together?

RE: Extensions to small buildings

Snatch,

My thought is that the footing should be kept independant of each other.  Presumibly the existing building has been in place for some time, so the building has had time to settle.  The soil under the new portion of the building has not been subjected to loading, so when the new portion is built, the soil there WILL settle.
If the footings are connected, cracks will likely develop due to deiiferential settlement.

As for the beams.  You can contect the new beams into existing columns (capacity depending) and load the existing footings.  The "increased" settlement in the footings would likely be neg.

Just my thought.
Cottage Guy

RE: Extensions to small buildings

Another problem with connecting new to old is that you may then have to bring the old up to code.

RE: Extensions to small buildings

It all seems doable, until you start thinking of Seismic design of your new "structure". At that point, you then must decide how you will analyze this composite building, yada, yada, yada...

Save yourself the trouble, separate the buildings enough to allow both to deflect the requisite inelastic deflection in an earthquake, if you can.

RE: Extensions to small buildings

Hello Trainguy, which seismic region are you from?  Southern California engineer here.

Separating the structure makes lateral calculation simple but you end up with real thick walls at the separation and the joints have to be replaced everytime there is a severe seismic movement.  Assuming the building is designed properly, hopefully the separation joints are the only thing you have to fix.

RE: Extensions to small buildings

I'm posting from Montreal, Canada. We are actually in a somewhat active seismic zone here, but I don't quite remember its exact designation as I've started working exclusively on railcar structures for the past few years...

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