How to decide to convert your house into a two-family house


Dear Monty: I need to know if I can convert my single family home to a two family home. The second thing is, if so, what are the legal rules of transformation?

Monty’s Response: The rules you are looking for are not uniform across the United States. There is no federal building code except one. The Department of Housing and Urban Development has a code for the design and construction of manufactured homes. Building codes protect public health and safety. According to, the International Residential Code (IRC) is “the complete stand-alone residential code that creates minimum regulations for single and two-family dwellings. It combines all provisions of building, plumbing, mechanical, combustible gas , energy and electricity for single family and two family residences.Each municipality controls the codes, so if you live on the border of a city and your neighbor lives across the line in a suburb , permitting construction or renovation projects could be different.Always locate the municipality of your property for permit and code issues.

The process

–The first step is to contact the municipality. Most of the information you need could be online. The zoning office is your first stop to find out if they allow a two-family home. Suppose you live in a development that has a homeowners association. In this case, that’s your second stop, because HOAs usually have rules that can affect your decision.

–Once you have passed the zoning test(s), there may be several departments to check. The larger the municipality, the greater the likelihood of a more complex process. Other possibilities are a building inspector, building code office, planning department and maybe more.

–You may need to provide a scaled floor plan, depending on the extent of the renovation, and a building permit, which requires a fee. Avoid mediocre floor plans here.

–After determining the legal steps to take, you decide if this is a smart decision. Many owners say cost isn’t an issue when they start out, but regret it when it comes time to sell.

Here is a list of information you need to determine if the project makes sense.

#1: How much will it cost, all inclusive?
#2: What is the “as is” value of your home?
#3: How much do similarly converted homes sell for in your neighborhood?
N°4: What are the rents in the neighborhood?
#5: Who will do the actual work? If you need a contractor, how much will it cost? If you do the work yourself, are you qualified? Do you have the time? Have you made a list of materials?

Almost done

Assuming everything makes sense on paper and pencil, just one more test. Compare the “as-improved” cost of the renovated home plus the expected rental income with the cost of selling and buying a newer or newer unit built as a two-family home.

Quick Warnings

A remodel is not a project to practice. What you learn on TV does not turn into experience. Suppose you didn’t grow up in the trades. In this case, you’re probably better off paying craftsmen or an experienced general contractor. Always get the required permits, because if you don’t sell later and disclose this, it presents a costly potential liability. Also think about what it takes to be a good landlord.


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