Although these are three different problems, they are often interrelated and two or all three may be experienced together as you walk around a house during a showing with your realtor, especially in an older home. The flexing of bouncy floor joists, for example, can cause the subflooring fasteners to work loose and squeak. When the subfloor is plywood, this will be more noticeable over the edge where two sheets abut on top of a joist or wood floor truss at the middle of the floor. Severe notching of floor joists, like in the photo below, will also weaken the floor structure in the area around it.

    Even new houses can have this problem if the floor framing members are undersized, spaced too far apart, or installed without adequate fasteners. The gold standard for installation of a plywood subfloor is “glued and screwed."

    The problem can be minor and easily fixable, or big and expensive. Squeaking of a few loosened nails in an otherwise sound floor can be fixed from above or below with a couple of well-placed screws. If, however, the squeaking happens at multiple locations and the floor has a noticeable bounce, the floor structure will have to be stiffened with a new support beam, bridging, or sistering additional joists to the existing ones before tackling the squeaks—and that can get expensive.

    Spongey spots in the floor can be termite damage or wood rot from long-term moisture intrusion, and extensive termite damage can mimic other floor structure problems. 

    Which professional to call? Although you could go directly to a building contractor, it is usually best to start with an engineer that can diagnose the problem and prescribe a specific remedy for a contractor to follow. Because you don’t own the house yet, and probably won’t get permission from the seller to open up concealed areas, only an approximate estimate may be possible, and the estimate may make you decide to move on and look at other properties.

    By the way, if you feel any looseness or irregularity in the floor underfoot, we suggest you ask for silence in the house as you walk around and feel for soft or bouncy spots and listen for squeaks. It is not unusual for a seller have music or a TV on during a showing to conceal the creaky sounds in an old house floor.

    Also, see our blog post Should I buy a house with sloping floors?

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Here’s links to a collection of our other blog posts about STRUCTURE AND ROOMS:

• Why is the grout cracking and coming loose at my floor tile?

• What are the building code requirements for notching and boring holes in a wall stud? 

• What causes dark or light "ghost" lines on ceilings and walls?

• Can you access or exit a bedroom through another bedroom?

• What is the difference between a carport and a garage? 

• What are simple ways to find the cause of a ceiling stain?

• What is the minimum size of habitable rooms in a house according to the building code? 

• Why is my garage ceiling sagging? 

• How can I identify what kind of wood flooring I am looking at?

• Why does my concrete floor slab sweat and get slippery?

• What is the minimum ceiling height for rooms in a house? 

• Why are there score line grooves in the concrete floor of the garage?

• How much can I cut out of a floor joist? 

• How can I tell if my floors are sloping?

• Why do the floors slope in this old house? 

• What are the common problems when a homeowner converts a garage to conditioned living space, such as a family room?

• How can I tell if a wall is load-bearing? Which walls can I take out? 

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