The slope of a floor is crucial for safety and comfort. Because of that, carpenters and other construction professionals need to know the correct way to level a surface so that their structures are as safe and structurally sound as possible – and that’s where measuring floor slope comes in.
Here’s how you can measure floor slope:
- Measure floor slope using a carpenter’s level
- Measure floor slope with a plumb bob
- Measure floor slope using a clinometer
- Measure floor slope using a laser level
Read on for the steps to follow when using each method and what to consider when checking floor slope.
1. Measure Floor Slope Using a Carpenter’s Level
A carpenter’s level is a device that can be used to measure slope. It consists of a rectangular board, called the “leveling head,” mounted on two metal rods or tubes at right angles to each other and joined by springs so that it can pivot freely in any direction. In addition, the leveling head has a vial of liquid (usually mercury) that indicates when the surface being measured is horizontal.
To measure slope using a carpenter’s level, you need the following materials:
- A steel carpenter’s level marked in both feet and inches. This will give you different readings for the up-angle and downslope. If you’re on the market for one, I recommend this WORKPRO 3-Piece Spirit Level from Amazon – it’s durable, lightweight, and comes with easy-to-read, high-visibility bubbles at each vial.
- Tape measure
- Masking tape
Here are the steps:
- Level your carpenter’s level on the floor to point straight along the line to be measured. Verify that zero is centered in the bubble(s) on both sides of the level vial. Make sure you are holding this flat as well since any angle will distort your reading!
- Create a zero reference point at one end with a piece of masking tape. This will be your up-angle reference point for zero degrees and 45 degrees up (or 0 deg). Your other end should have no elevation reading on the builder’s level display.
- Measure your distance to the up-angle reference point you created from the left side of your carpenter’s level. This will be in feet on one end and inches on the other – since you’re measuring slope, this is your downslope reading, while points closer to zero degrees are considered positive slopes (uphill).
- Subtract the up-angle reference point from your downslope reading and divide by the number of feet. So, if you’re measuring a slope with a carpenter’s level that is -0.25 over 12 inches, then .125/12 = 0.008333 or about +/-0.833 degrees
Here’s a 5-minute video that describes these steps:
Using a carpenter’s level to measure the floor is simple and easy to use. However, the measurement is not exact, but it should be close enough for most purposes.
2. Measure Floor Slope With a Plumb Bob
To measure the slope of a floor surface, you will need two string lines. One line is 1 foot (.30m) long, and the other is 6 feet (1.8m) long. The hub or tulip end should be placed at the opposite end from where you are standing.
The steps are as follows:
- Place one string line in front of the plumb bob to go down into the top clamp directly below.
- Angle your other string line on an arc across to finish up next to where it started with just enough drop for each 6-foot (1.8m) length.
- Measure how many inches above or below horizontal this second string falls and then calculate how much slope that corresponds to using this equation: Slope (in degrees) = sin (elevation difference in inches)
You can also use this equation to find out the pitch of your roof or other flat surfaces that are not as easy to measure using traditional methods such as measuring angles and reading trigonometric charts.
The slant height you’re looking for when calculating the elevation change should be measured from ground level up before starting any calculations.
Caveat: This method is relatively easy, but it only works on floors without obstructions like radiators or vents. These objects create bumps that distort readings obtained by string lines.
3. Measure Floor Slope Using a Clinometer
A clinometer is a vertical instrument for measuring the angle of a slope.
Clinometers can be used to measure the angle of elevation or depression and are often considered more accurate than using carpenter’s level because they use laser beams instead of gravity-based bubbles that may not read accurately on other slopes.
To measure floor slope with this method:
- Place one end of the clinometer against an even transition from floor height (e.g., door molding) and extend your arm fully, holding steady as you hold onto the other end perpendicular to its first position, so it forms an “L” shape–or a skewed “T.”
- Read off what number displays in degrees on the reading gauge at the top. This will indicate the angle of elevation or depression.
This doesn’t require gravity to be accurate, so it’s reliable on slopes. However, it’s more expensive than the other methods and can take a while to measure the slope accurately.
4. Measure Floor Slope Using a Laser Level
A laser level is an optical instrument that allows you to build straight lines and get accurate measurements for your home improvement project. For example, you can also use a laser level to measure floor slope so that you know the best way of installing laminate flooring or carpet tiles on your new hardwood floors.
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To measure your floor’s slope using this gadget, follow these steps:
- Place the laser level on one side of your floor and let it self-level.
- Mark where it lands with a piece of chalk or any non-permanent marker.
- Repeat this process at various points around the perimeter, making sure to cover any slopes in between these markers.
- Connect the dots that form to create a line.
- Once you have created all lines connecting the marks, measure how many inches they are from each other across the surface (the distance is directly proportional to slope). The further apart measurements are, generally speaking, indicates steeper inclines, while close together measurements indicate less steep inclines.
This video illustrates how to measure floor slope using a laser level:
This method gives accurate results, but it’s expensive.
What To Consider When Measuring Floor Slope
Floor slope can have a huge impact on how comfortable and safe you feel in your home. Here are a few things to consider when measuring floor slope:
- Is there a difference between the height of two points across the span of one foot? This could indicate an area where water may pool, or mold might grow due to excess moisture.
- Do stairs have any gaps at their edges? Gaps around stair edges may mean that people with mobility issues will experience difficulty navigating them safely.
- Are all door thresholds level? Thresholds should be level so as not to trip anyone who has vision problems or to prevent water from pooling beneath the threshold during a storm.
The most important thing is that you take measurements of your home and know of any potential dangers not to exacerbate existing conditions. You might be surprised by how many changes you can make to improve safety, comfort, and overall quality of life for everyone who lives there!
Final Thoughts
Floor slope is one of those things that you might not think about until it’s too late. It may seem like a small thing, but when your floor slopes in the wrong direction (e.g., down), it can cause serious problems with your home or office structure and even safety hazards for people living there!
Therefore, it’s critical to measure your floor’s slope to ensure you always avoid such risks. Whether you’re using a carpenter’s level, clinometer, plumb, and bob, or laser level, ensure the tool is calibrated correctly to provide accurate measurements of an incline in degrees.
