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Measuring the Subfloor

Before measuring for flooring, it is important to understand the subfloor beneath the flooring material. The subfloor is the base layer of any flooring surface, as it provides support and stability for the flooring material. Measuring the subfloor accurately is essential to ensure the proper installation of the flooring, as well as to ensure the safety of the people using the floor.

In this guide, we will discuss how to measure for flooring and the importance of accurate measurements:

How to measure for flooring

A subfloor is the structural foundation of a floor that is installed directly under the flooring. Subfloors are typically made of either plywood or OSB (oriented-strand board) and are held in place by nails, screws, or staples. They provide both structural support and stability for the floor—without a subfloor, your finished floor can sound hollow when walked upon and won’t last as long.

It is important to know what kind of subfloor you are working with before you can move forward and measure it correctly. Because thick wood on top of a concrete slab needs different measuring techniques than plywood covering an existing wood frame, it’s important to understand all the steps so you can get accurate measurements. Once you begin measuring your subfloor, here are some tips to follow:

  • Measuring all areas separately will minimize measurement errors
  • Think twice before investing in ordinary length rulers since they become less accurate with time
  • Use a metric length ruler with 1mm divisions for best accuracy
  • Ensure that your ruler is perpendicular to the subfloor so your measurements aren’t skewed
  • To check accuracy double check calculated measurements with actual widths/lengths

What is the purpose of measuring the subfloor?

Measuring the subfloor is the essential first step when preparing for any flooring project. As the foundation of any structure, the subfloor supports all other flooring materials and must be in good condition in order to avoid problems later. It is important to establish if there are any existing irregularities or damage that needs to be addressed prior to installation.

In addition to being properly leveled and secured in place, knowing your substrate is key to understanding what type of flooring you can use – as some types may require special materials or preparation prior to installing your chosen floor. Depending on your project, measuring the subfloor will help you determine what sort of underlayment or additional support may be necessary before moving forward with your installation.

It’s a good idea to take detailed measurements of each area so you know exactly how large each space is before purchasing materials. Identify irregular shapes, notches, and other details that make up the unique character of your space and record these measurements with accuracy down to 1/16th inch increments for optimal precision.

Tools Needed

Before you start measuring for your subfloor, it’s important to make sure you have all the tools you need. This includes:

  • Measuring tape
  • Level
  • Pencil
  • Calculator
  • Chalk line

Measurement accuracy is key when it comes to installing a new floor, so it’s best to make sure you have the right tools before you start.

Tape measure

Tape measure is an essential tool when measuring a subfloor. Tape measures are available in varying lengths, making them ideal for taking measurements in a variety of settings. To get the most accurate measurements, make sure to choose a tape measure that is at least 25 feet long and has a 1/16 inch graduation.

When measuring the subfloor, use the hook end of the tape measure to place it at one end of the measurement and then pull it tight until you reach the other side of your measurement. With most measurments for a subfloor, it is not necessary to include fractions – but if needed, simply read off what fraction appears on the tape measure after allowing some slack. Doing so will ensure more precise measurements when laying down flooring material and will make all calculations with roof joists much easier.

Pencil or pen

A pencil or pen is an essential tool when measuring a subfloor. It is necessary for recording any measurements that are taken. Making sure you have the right type of pencil or pen is essential in order to make sure your measurements are accurate and clear.

A graphite pencil, such as an HB pencil, will usually be sufficient for recording your subfloor measurements. However if you plan on marking out large sections of the floor or have a particularly hard surface to mark onto, then it might be worth investing in a thicker lead graphite option such as an H2 or H3.

Depending on how important accuracy and visibility of the markings are, it could also be worth using a permanent marker pen instead of a regular pencil. This may also help in case anything needs to be measured again at a later date as the marks can still remain visible even when rubbed off with an eraser.


A notepad is a useful tool when measuring your subfloor in order to record the measurements that you take. It is recommended to use lined paper so that it is easier to ensure that all measurements are as accurate as possible. It’s important to note the measurement in both feet and inches, regardless of how you plan to reference the size for later use.

Note any walls, doorways, pipes or other obstacles you encounter during the measurement process so that your calculations will be more accurate later on. When all of your measurements have been taken, use a calculator or math calculations to add up all of your measurements in order to get a firmer understanding of the size of space available for laying down new flooring:

  • Measurement 1
  • Measurement 2
  • Measurement 3
  • Measurement 4
  • etc.

Measurement Steps

When looking at how to measure for flooring, it’s important to start with an accurate measurement of the subfloor. This is important because it helps you determine the size and shape of the flooring area you’ll need. Furthermore, it allows you to make any modifications you need to the space for a better fit.

Here, we’ll discuss the steps for measuring the subfloor accurately:

  • Step 1: Measure the length of the room.
  • Step 2: Measure the width of the room.
  • Step 3: Measure the distance from the walls to any obstacles, such as a fireplace or built-in cabinetry.
  • Step 4: Measure the distance from the walls to any doorways or openings.
  • Step 5: Measure the distance from the walls to any windows.
  • Step 6: Measure the distance from the walls to any radiators or other heat sources.

Measure the length of the room

Measuring the subfloor of your room is an important and crucial step in any flooring project. To accurately measure, it’s important you measure the length and width of the room. Measuring to determine the size of your project also helps you calculate how much flooring material you will need. To avoid wasting material and money, proper measurements are key to having a successful floor plan.

To get accurate measurements, measure each wall separately—you may find that some walls are longer or shorter than others. Begin by measuring from one corner of the room to the opposite corner. Use a tape measure or retractable string line for accuracy. Don’t forget to account for door frames, closet spaces and other obstructions that may alter the amount of material required for installation. If there is any question about measurement accuracy take multiple readings along walls as each wall can be slightly different from one end to another due to crown molding or trim work around doors or windows.

Once all dimensions have been recorded, calculate total area by multiplying length by width for square footage required for your project. By using correct measurements you can ensure that you have enough material on hand before beginning installation which can help save time and money down the line!

Measure the width of the room

In order to accurately measure the subfloor, it is important to start by measuring the width of the room. Take a tape measure or laser measuring device, and measure from one outside wall of the room to the other. Be sure to take measurements in multiple places throughout the entire room, as even slight differences in wall width can cause major problems later on.

This measurement will be used to calculate how much material is required for your subfloor installation.

Measure the height of the room

Measuring the height of the room is a critical factor when preparing to install flooring. Knowing the exact height of each wall will ensure that the correct amount of material is purchased and that there will be an adequate clearance for any doorways or other structures.

To measure the height, begin by partially closing a large door in the room. Using either a yardstick or small ruler, measure from one of the top corners to the bottom corner then open and close the door several times to complete this measurement. Record this number as it may be necessary to make adjustments later.

Next, measure from one end to determine total length of all four walls including any cutouts or curvature, making sure these specifications are mentioned correctly on your measurement chart. Measuring around all regular walls should take less than ten minutes but at this time you can also include other objects such as electrical outlets that may need to be trimmed in later stages of construction. Make sure any irregularities are noted on your chart, along with measurements for windows, closets and closets doors before moving onto step two – measuring subfloor flatness.

Calculating the Area

Before you begin installing a new floor, it’s important to measure the area of the subfloor. This ensures that you purchase the correct amount of flooring material and helps you plan the layout of the floor. Determining the area of the subfloor also helps to account for any irregular furniture and corners.

In this article, we’ll discuss how to measure the area of a subfloor accurately:

Calculate the square footage of the room

When measuring a space for subfloor material it is important to calculate the exact area so that you purchase the right amount of flooring to finish the project. To calculate the square footage of a room using simple math, measure each wall within the room and then multiply the length of each wall by its width. Add all of these numbers together to get your total square footage.

For example, if one wall measures 12 feet by 12 feet, and another wall is 10 feet by 10 feet, you need 244 square feet of subfloor material:

  • 12 x 12 = 144 sq. ft
  • 10 x 10 = 100 sq. ft
  • = 244 sq. ft

When measuring your walls use a tape measure or layout square to account for any irregularities or angles in your room such as alcoves and bays. Exact measurements are necessary as an excess can cost more than waste and an under purchased amount can potentially ruin a flooring job. Additionally, you will need some extra coverage when ordering subfloor material as a buffer against any seams that may be visible when laid down over uneven surfaces or imperfections in the existing floors underneath.

Calculate the amount of flooring needed

When measuring a subfloor, the first step is to calculate the amount of flooring you will need. This can be determined by measuring the total area to be covered in square feet and multiplying it by a factor based on room measurements.

For example, in larger rooms with one or more walls that are 8 feet or longer, you should measure each wall’s length and width separately and add them together (the total should be rounded up to the next square foot) for your material calculation.

Other factors that influence this calculation include:

  • Doorways
  • Closets
  • Edge pieces (such as around fireplaces or stoves)
  • Stairs

All of these elements should be taken into account before making a final measurement for your material purchase. When calculating the square footage needed for a room without an even number of walls, it’s best to measure each segment around the room individually and add the totals together in order to make sure you have enough flooring materials on hand when installation begins.


Having a well-measured subfloor is essential for a successful flooring installation. We’ve gone over in detail the steps you need to take when measuring your subfloor which include measuring the width, length, and elevations of the area. Taking the time to measure the subfloor properly will ensure that the end result of your flooring installation is perfect.

Let’s analyze the key points of this article one last time:

  • Measuring the width, length, and elevations of the area.

Summary of steps

The overall process of measuring, documenting and presenting a subfloor can be broken down into a few key steps:

  1. Start with measuring tools such as a tape measure, level and chalk box. Begin by doing a site survey to assess the floor size and take note of any obstructions.
  2. Document all measurements in tabulated form for easy reference. Include information about the type of flooring, floor area (length x width), location of obstacles and doors, etc.
  3. Prepare the appropriate drawings to depict your findings in an understandable format for others to use in planning their projects or designs. These should include accurately scaled drawings depicting outlines of walls, door openings and any other obstructions pertinent to the space.
  4. Calculate final dimensions for each area defined by your drawings taking into consideration distances from walls and edges as well as any obstructions; determine total square footage of the subfloor which is necessary for ordering materials like tile or carpeting; analyze the amount of leveling or patching needed prior to installation; consider eventual removal issues when calculating access needed by tools used during removal process if applicable; provide written suggestions on best possible way fitting material around existing fixtures if requested; offer written advice concerning adhesion products when requested during inspection process; etc. This step is critical so that you have an accurate understanding of how much material is needed before making any purchases or beginning any installations.
  5. Finally, give written recommendations concerning best practices related to underlayment use, cutting methods and other considerations that are important factors when measuring a subfloor properly. Provide safety information related to working with power equipment such as saws when handling materials like tile or wood materials which may contain splinters or sharp edges that could cause injury after completion of install phase if not managed carefully beforehand. These measures will help protect both you and your customers from avoidable injuries during this project phase.

Tips for a successful flooring installation

A successful flooring installation begins with a sound and level subfloor. A few straightforward steps such as measuring and checking the subfloor will help ensure a successful outcome. Planning ahead when measuring the subfloor is key to ensure you have enough supplies on hand.

Measuring Tips: Measure the widest and longest points, take into account walls, doorways, closets – any irregular shapes which will have to be accommodated. Once all measurements are collected, add an extra 10 percent for cuts and waste for materials you may need along the way.

Subfloor Inspection Tips: Ensure your subfloor is level before laying your new flooring so there are no bumps or dips. Starting from one corner check to another, measure down from one corner to the other using a long level or a straight edge- Remember to always check at least three areas of each room to verify that there are no low spots in your floor. Note: If any of these differences in height exceed 3/16” follow manufacturer instructions for specific making corrections in height. Also check for water damage with a moisture meter; sometimes floors can retain moisture so it’s always important to make sure it’s dry enough prior to installation starting.

Floor Prep Tips: Vacuum up all dust and debris created when taking out old flooring surfaces and moving furniture around such as adhesives that may remain on the concrete after a tile was removed or carpet padding residue still left behind which may provide an uneven surface causing future complications. Eliminating this potential problem before beginning installation can save time and money further down the line!