We get calls every week with people asking about adding another home to a single family home to create a duplex, or converting a garage behind a duplex to make a triplex, or just adding a small accessory dwelling.
Effectively, these are all the same from a design and building perspective.
The permit process varies quite dramatically and can take 6-12 months no matter which path you choose.
The one big cost impact is a duplex or triplex will incur new utility hook up fees of $15,000+. Otherwise, it’s just a matter of a 6 month permit process or a 12 month permit process.
This is very specific for Berkeley however most cities are very similar.
Here is a summary:
1) You own a single family home and want an accessory dwelling
– If you keep the design under the height limits and are willing to sign a deed restriction promising to owner-occupy one of the two units for eternity, then you can skip the planning permits with a “by right” planning approval. Then you get your buiding permit which is 5+ months.
– If you want a design that is over the height limit of 14′ then you can apply for an AUP planning permit which costs about $4,000 and takes 5+ months. Then you get your building permit, which is another 5+ months.
2) You own a single family home and want a duplex.
– If you are zoned for two units, then the city may allow this. The architect has to check at the planning desk.
– Planning will require a Use Permit that has neighbor review and takes about six months for the planning permits. Building permits will follow
3) You own a duplex and want to add a third unit:
– – Same as above. You might want to just make it a big addition to the duplex and keep it as two units or you might want to permit the 3rd unit. Again this requires the architect to visit the city.
In either case, the cost is about $6,000 for the Use Permit
Utility hookups come into play, so that is an additional ??? (I’d say $15,000 or more)
Building permits are the same as they are based on building costs.
Also check out the permit calculator: http://www.ci.berkeley.ca.us/PermitFeeEstimator.aspx