How do I measure floor slope at home?

A marble or small ball shows you direction — where it consistently rolls is downhill. A long spirit level laid on the floor gives you a local reading and shows which way the tilt runs. Neither substitutes for a survey, because both only measure between two points and neither maps the whole floor plane. What they do well is help you describe the shape of the problem before anyone arrives: which rooms, which direction, where it is steepest.

Is a sloping floor always structural?

No. Almost every house has some slope, including new construction — perfectly level floors are a construction ideal rather than a reality. Original construction irregularity, additions built to a different datum, and previous repairs all show up as slope. What matters is the magnitude, the distribution across the house, and whether it is changing. A survey establishes all three; a marble establishes none of them.

Does foundation type change how slope reads?

Yes, and usefully. On a slab home, slope usually reflects movement of the slab itself, and the pattern tends to be broad — falling toward a corner or along one elevation. On a pier-and-beam home, slope can come from settled supports or from the framing above them, and the pattern is often more localised: a dip along a girder line or springiness between joists. The shape of the slope is a clue to which.

What is the difference between slope and a dip?

Slope is a consistent fall across a distance. A dip is a localised depression that comes back up again. They point at different things — a broad slope suggests something affecting a whole area of support, a dip suggests a specific member or support beneath that spot. Recording which one you have is genuinely useful information.

What does an evaluation add to what I can see?

Measurement across the whole house, referenced to a single datum, producing the shape of the floor plane rather than a set of impressions. That shape is what distinguishes settlement from heave, identifies where the problem is concentrated, and provides a baseline for measuring change later. It is the single thing you cannot produce at home, and it is why the survey is the core of an evaluation.

Uneven or Sloping Floors: What to Document

The observation behind a lot of enquiries on our common foundation concerns page, and how to record it properly.

Almost every house slopes a little

Start here, because the alternative framing causes unnecessary alarm.

Perfectly level floors are a construction ideal. Real houses settle during their first years, have additions built to slightly different datums, get previous repairs that recovered some but not all of a differential, and are built by people working to tolerances rather than to laser precision.

So the question is never “does my floor slope”. It is how much, over what distance, in what pattern, and whether it is changing.

What you can usefully observe at home

Direction. A marble or small ball placed on the floor rolls downhill. Try it in several rooms and note which way it goes in each. Consistent direction across adjoining rooms tells you something; different directions in different parts of the house tells you something else.

Local reading. A long spirit level laid on the floor shows tilt over its length and which way it runs. Move it around and note where the tilt is steepest.

Feel. Walk the house barefoot. Slope is often perceptible before it is measurable with household tools, and soft or springy spots are as important as sloped ones.

Furniture and fittings. Gaps under the base of a cabinet that used to sit flat. A door that swings shut on its own where it did not. A bookcase that needs packing at one corner.

A long spirit level laid across a wooden floor showing a visible tilt in the bubble

Slope versus dip: a distinction worth recording

A slope is a consistent fall across a distance — the floor drops steadily from one side of a room to the other and keeps going into the next room.

A dip is localised — the floor falls and then comes back up again, often along a line or in a specific area.

These point at different things. A broad slope suggests something affecting support across an area. A dip suggests a specific support or framing member beneath that spot — on a pier-and-beam home, frequently a girder.

Recording which one you have, and where, is more useful than any single measurement.

Slab and pier-and-beam read differently

	Slab home	Pier-and-beam home
Typical slope pattern	Broad; falling toward a corner or elevation	Can be broad or localised
Dips along a line	Less common	Often follows a girder
Springiness underfoot	Rare	Common; points at joists
Can be inspected underneath	No	Yes
Likely causes	Slab movement from soil	Support settlement or framing

On a crawlspace home, half the diagnosis happens underneath, which is why an evaluation of a pier-and-beam home that skipped the crawlspace is incomplete. See sagging floors and pier-and-beam homes for the mechanisms.

Hand-drawn floor plan sketch with notes about which rooms slope and in which direction

A simple documentation method

Sketch a rough floor plan of the house. It does not need to be accurate — room shapes and relative positions are enough.

On it, mark:

An arrow in each room showing the downhill direction
Where the slope seems steepest
Any localised dips or soft spots, marked distinctly from slopes
Which doors bind, and on which edge
Where you have noticed cracking, inside and out
The date

That single sheet of paper tells an evaluator more in thirty seconds than a conversation does in ten minutes, and it becomes a dated record you can compare against later.

What the survey adds

A relative elevation survey measures floor height at points throughout the house, referenced to a single datum, producing the shape of the floor plane as a whole.

That gives you three things your marble cannot: magnitude, distribution, and a repeatable baseline. It is what distinguishes settlement from heave, identifies where a problem is concentrated, and lets a second survey in twelve months establish whether anything is moving.

When to get it measured

When the slope has changed, when it is accompanied by cracking or binding doors, when a floor has become soft rather than simply sloped, when a dip has appeared, or when you need documentation for a sale. If binding doors are part of the picture, sticking doors and windows covers what to record about those separately.

Monitor if the slope is longstanding, modest, and unaccompanied. Sketch it, date it, and check again in six months.

A foundation evaluation produces the survey. For the full set of observations, see common foundation concerns.

Uneven or Sloping Floors: What to Document Before an Evaluation