Half of a duplex is essentially a single family residence attached to another single family residence, with a common wall between them. Duh…that’s obvious, but let’s go with it. So the separating wall is the component that makes a duplex different from a freestanding house, and the wall provides both fire and sound separation between you and your neighbor. 

    A popular duplex floor plan puts the garages side-by-side, making them a sound buffer between the units. But, if you are considering a duplex with only a wall separating the two living areas, sound control is an important consideration. Some homes have a concrete block wall between sides that continues up through the attic to above the roof, which provides a barrier for both sound and fire protection.

    If not, a regular wood-stud frame wall transmits sound easily through the studs connected to the wallboard on both sides. One solution that reduces sound transmission is a staggered stud wall design, like in the diagram below, with insulation zig-zagging around the studs. This can sometimes be checked by removing a recepacle faceplate on the common wall and gently probing the depth. 

    Fire separation, to keep a fire on one side from rapidly spreading to the other, is the second consideration. The building code requiring a fire-rated wall between sides has been around for about the past 30 years. To learn more, see our blog posts What is the code requirement for fire separation in attic between sides of a duplex? and When was a fire separation in the attic first required between sides of a duplex?

    Other than sound and fire separation concerns, a duplex has the same common problems as a regular single-family house. You can use the links below to read other articles about evaluating a house based on the era, location, previous history, or type of construction you are buying. 

• What are the common problems to look for when buying a 1950s house?

• What are the common problems to look for when buying a 1960s house?

• What are the common problems to look for when buying a 1970s home?

• What are the common problems to look for when buying a 1980s house?

• What are the common problems to look for when buying a 1990s house? 

• What are the most common problems with older houses? 

• What are the problems to look for when buying a homeowner remodeled house?

• What are the problems to look for when buying a homeowner remodeled house?  

• What are the common problems to look for when the plumbing has been replaced in a house?

• What problems should I look for when buying a country house or rural property?

• What problems should I look for when buying a house that has been moved? 

• What problems should I look for when buying a house that has been vacant or abandoned?

• What should I look for when buying a house that is being "flipped" by an investor seller? 

• What do I need to know about buying a foreclosure?  

• How do I recognize serious structural problems in a house? 

• What are the pros and cons of concrete block versus wood frame construction? 

• Should I buy a house that needs a new roof?

    Visit our COMMON PROBLEMS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Illustration by Code Check.