Duplex-Triplex-Quad-plex-Owner/builder Multifamily Homes

Dear Readers,

I am republishing my 4-plex article along with another question, as interest in building 2 and 4 unit, as well as 3 unit multiplex homes has increased.

Multifamily homes, whether they consist of 2, 3, or 4 housing units, is a good way to get a nice home for yourself that someone else is paying for, at least in part, and in some cases all of it!

Photo courtesy of Building Designs By Stockton

Most people would be surprised as to the number of residential lots in any given city that are already zoned for duplexes, and in some cases 3 or 4 unit dwellings.

You can check with your local zoning department where you live, as they will have a record of such properties.

Most locales will also allow, as will lenders, owner/builders to construct up to and including a 4 unit structure without hiring a licensed general contractor, AS LONG AS YOU OCCUPY ONE OF THE UNITS!

Any residential dwelling with over 4 units, or any non-owner occupied dwelling, is considered a commercial building, and requires a commercial license and a whole new ballgame as to investment property financing.

Your work load as an owner/builder will be increased building multifamily because building 2, 3, or4 homes at one time will require more planning and more of your supervision.

No pain, no gain, right?


Hello Carl,
“I was just reading some of your stuff. I have a question that I will try and make as simple as possible. I have already the property for such, but have just recently entertained the thought of building a four family house.

My question is (ballpark), how much can I expect this type of project to cost me?”

Hi Carl,
“I’m thinking of buying a fixer upper house that needs to be demoed. I want to do a triplex, each with about 1200 sq feet and each as a 2 bed 2 bath.

I have an idea what I want to do, but I can’t draw very well.

Can you tell me what estimate cost it would be a ballpark range.

Thank you for your time. (Should I buy my own materials?)”


Hi Guys,

A four unit house (4 plex) will cost at least 4 X the price of 1, maybe more.
A three unit house (3 plex) will cost at least 3 X the price of 1, maybe more.
A two unit house (duplex) will cost at least 2 X the price of 1, maybe more.

The “economy of scale”, that is, the price per sq ft drops as the house gets larger, is mostly overridden in “plex” building, by increases in the number of kitchens, baths, HVAC units, parking, garages (if any), etc., as well code compliance for multi-family (fire walls, sound proofing, visitor parking, etc.), as well as permit costs.

Use the cost to build calculator on my “Getting Started” page and, based on your zip code, calculate the cost to build one unit. I would recommend using the “Minimum Quality Class”.

And Daniel, YES, buy your own materials!

Both of you need to check with your local building inspection dept. to get more precise requirements before you get too far into the planning.

Here are some plans for 3-4 plex units: Building Designs By Stockton

Good luck, Carl Heldmann