Why do the floors slope in my house?

Monday, October 1, 2018

Three Reasons For Sloping Floors

Of the three reasons for sloping (out-of-level) floors in a house, one of them was may have been built-in when the house was constructed and the other two have occurred over the years.

Let’s start with the built-in slope.

    It’s necessary to pitch the floor on an open porch slightly to cause blown rain to run off, like in the photo below. This eliminates puddling water, which quickly develops wood-rot underneath. In an effort to create more indoor living space the porches in old houses often get enclosed into rooms, but the floor slope toward the new exterior wall remains. Because sleeping porches were popular around Gainesville and most of North Florida in the era before air conditioning, and some were the shape of a small bedroom, it may not be immediately recognizable that a room was once a porch.

And the second reason is a structural problem.

    This can happen in several ways: the ground under the supporting piers can settle, or heave upward in areas of clay soil, or the piers themselves can deteriorate and begin to collapse and tilt over, or the supporting floor beams or joists sag due to rot or termite damage. A look in the crawl space under the affected area will usually clear up the mystery.

Undersized Floor Framing Lumber

   The third reason also relates to a structural problem: undersized floor framing lumber. When the floor joists are too small for the weight of furniture, appliances, and the people walking across them, they sag. And the sagging typically progresses and becomes more noticeable over the years, especially if termites have weakened the floor joists even further over time. This type of floor slope is different from the first two, in that the floor slopes towards the center of the room instead of from one side to the other, and it’s also usually accompanied with a noticeable bounce when you walk across it, along with rattling of small objects in cabinets or on table tops.

   We recommend that you leave the crawling around under a house to someone like us who does it for a living, and wears protective equipment for the job. But you can often figure out most of what’s going on under the house by viewing it with a flashlight from any available openings in the perimeter. If there are several “temporary piers” or stacked blocks or wood, like in the photo below, that’s a sure sign of a structural deficiency in the floor framing.

   As part of our home inspection, we note any sloping floors and attempt to determine the cause of the problem. When the floor slope in significant, it’s usually accompanied by other signs of structural problems, such as wall cracks, jammed doors and windows, and cracked window panes. Structural repairs may be necessary. But if the floor slope is barely noticeable and there are no visible structural problems under the home, it might be best to chalk it up to “old house character” and enjoy the little quirks of your vintage home.

   To learn more about how to determine if a floor is out-of-level, go to our our blog How can I tell if my floors are sloping? 

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

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? 

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.

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