Selection rules and requirements for floor joists

For any flooring-related construction or renovation project, selecting the appropriate floor joists is essential. The vital structural components known as floor joists sustain the weight of floors and everything on them, including people and furniture. They give the floor above stability and strength by bridging the space between load-bearing walls or beams.

A number of considerations are made when choosing floor joists in order to guarantee efficiency, longevity, and safety. These variables include the floor joists’ span, the weight they will support, the kind of flooring that will be put in, and any applicable local building codes or regulations.

The distance that the floor joists must span between supports is referred to as the span. In order to avoid sagging or structural failure over time, longer spans require thicker or stronger joists. Another important factor to consider is the load-bearing capacity. It establishes the maximum weight that the joists can bear securely without posing a structural risk.

The kind of flooring that is intended for the area also affects the choice of joists. Stronger joists are needed for heavier materials like tile or stone than for lighter ones like carpet or laminate. Selecting the proper joist dimensions and materials is made easier for builders and renovators when they are aware of these variations.

Selecting the proper floor joists is essential for long-term durability and structural integrity when building or remodeling a home. Because floor joists bear the weight of entire floors and everything on them, their selection must adhere to strict guidelines. Floor joist size and type are determined in part by span length, load-bearing capacity, and building codes, among other factors. By adhering to these rules, floors can maintain their strength and stability, which supports the overall structure’s functionality and safety.

Lags – what is it?

In a private home, putting in a wooden floor on joists is an outdated technology. Though there have been some modifications over time, the fundamental ideas still hold true. The benefits of this floor plan include dependability and simplicity. In theory, this explains the popularity.

What then are lags? In essence, the room is supported by these beams. They serve as the foundation for applying wooden planks. Generally, lumber is used for this, but it is important to note that products made of reinforced concrete, metal profiles, and even polymer materials are permitted when building private homes.

Wooden logs can also have a variety of designs. Naturally, an even beam that has been adjusted to specific dimensions is the best choice. because assembling, aligning, and modifying this material is simpler. You can use boards that are at least 50 mm thick that have been laid on edge. The boards are lost two or three if there is a significant gap between the supports beneath the lags.

Occasionally, even rounds or logs are utilized, which are first wiped to a level surface before a cow crate placed beneath the floor is placed on top of them.

Be aware that wood is not as good as the concrete base in certain areas. But she has a lot of great benefits:

  • low specific gravity, which practically does not create a load on the foundation and additional supports;
  • The floor base formed on the lags is ventilated, which significantly increases the life of the entire structure and the finish coating as well;
  • Between the lags you can easily place communication networks, and it will not be difficult to get to them in the event of an accident;
  • A heater is usually laid between the lags, which makes this design that meets the standards and standards;
  • using logs you can also level the floor structure, and this is much easier and cheaper if such a problem arises with concrete floors;
  • the strength of the log structure is not inferior to any other;
  • this design evenly distributes loads over the entire surface of the foundation;
  • the floor itself, laid along joists, is easier to repair.

Recently, water and resistive wooden floor joists in a private home have drawn criticism for their incompatibility with heating systems. The issue has been resolved today thanks to newly developed construction technologies. That is, it is not difficult to create a warm floor nowadays using wood.

Material for wooden joists

Timber is the best option, as was already mentioned. It is best to use less expensive wood for logs, such as pine, spruce, and other types. While larch elements are available, their cost is higher. Furthermore, selecting premium wood is not required for a lag structure. Savings are already possible because second grade timber is suitable.

However, it is preferable to avoid using inferior products. Naturally, looks are irrelevant in this situation, but the strength attributes need to be at their peak. However, wooden logs need to support heavy loads. As a result, you ought to avoid buying wood that has a lot of cracks, rotten rot, or blue spots. Such a lag structure is just not going to last very long.

Additionally, if the geometric shape of the wood has incorrect parameters, you should not purchase it. For instance, twisted, bent, or deformed wood. It will be challenging to match such content to the appropriate level.

As a result, it is advised to purchase wood that has been dried in designated facilities; the moisture content should not be higher than 12%. Additionally, you will need to set up storage conditions for the lumber if you buy it in advance. Recognize that materials with a moisture content higher than 15% will distort when operating due to temperature changes.

Take note! The beam’s cross-sectional area should have a height that is 1.5–2 times wider than its width.

However, this raises another query that has to do with the section itself. Specifically, which section is required in a given situation. But this isn’t the right place to begin. Additionally, based on two more parameters:

  • location of the logs relative to the room;
  • distance between them.

The first is easy to understand. As a final coat, boards are usually installed perpendicular to the wall where the window is situated. The issue is that the plank floor’s components are spaced apart. Furthermore, if you spread lumber throughout the space, the daylight streaming in through the window will show through all of the cracks. As a result, the logs are arranged across, or parallel to the window and wall. There is no difference in the method of laying the logs if sheet materials such as plywood, OSB, or chipboard serve as the foundation for the finishing coating.

Regarding the spacing between the logs, consideration must be given to the thickness of the flooring boards. Standard tabular data are available, and they are unique. Here, the ratio is:

  • board thickness 20 mm, joist laying step 300 mm;
  • thickness 24, step 400 mm;
  • 30 – 500;
  • 35 – 600;
  • 40 – 700;
  • 45 – 800;
  • 50 – 1000 mm.

It is important to keep in mind that the step that represents the laying of the logs does not always result in a round number. It needs to be rounded down as a result. Artists frequently install components with a smaller step close to walls. And you’re right. There is only one upside to this for the entire floor structure.

The separation in logs shown in the table:

Therefore, you can determine the beam’s dimensions for the floor logs if two parameters are known. However, it’s also important to realize that the computed value is reliant on the logs’ length in this case. Because an element sags more the longer it is. This implies that in order to avoid this issue, you will need to increase the cross-section. In other words, the beam’s length directly affects its cross-section. You can use the following table in this situation:

  • if the length of the span on which the timber is laid is 2 m, then lumber with a cross-section of 60×110 mm is used for this;
  • 3 – 80×150;
  • 4 – 100×180;
  • 5 – 150×200;
  • 6 – 180×220 mm.

As you can see, the material’s cross-section can be very striking. And this increases its mass in the first place, making the entire structure heavier as a result. Naturally, as the lag increases, so does its cost, and the budget grows accordingly. There is an easy way to solve this issue. The supports that the joists will rest on must be assembled at specific intervals. Small section lumber can therefore be applied.

For example, you can lay logs with a 50×80 mm cross section if you assemble support columns every meter. The measurements will be 50 x 90 mm if the step is increased to 1.2 m.

Note that the values shown are all minimum values. In other words, they can only be adjusted upward. These days, the space between the joists is frequently filled with thermal insulation material. And the better, the thicker it is. As a result, artisans frequently lay logs with a high height while leaving the width tabular.

And a single instant. The joist structure’s cross-section is also directly impacted by the spacing between its components. The thickness of the boards that can be placed on the floor decreases with decreasing step size. In accordance, the timber’s cross-section is lowered.

And the final item in the section about selecting lag material. Wood is a naturally occurring material that ages. In other words, logs can crumble, rot, shrink, and so forth. Furthermore, colonies of dangerous microorganisms could develop on its surface. The wood needs to be treated with specific protective compounds before use to avoid this, and there are plenty available on the market today.

These days, fire retardants are added to wooden products. These are substances that provide fire protection for the material.

Take note! Applying protective compounds to damp wood is pointless. In this instance, the maximum humidity allowed is 25%.

Log installation process

The installation of logs beneath wooden floors in private homes is done either on the ground, the foundation, or the floor slab. This is where we need to start. Let’s examine each option in isolation.

On the ground

It is imperative that a reservation be made right away to avoid having beams placed directly on the ground. Columns are poured from concrete or assembled from component parts to accomplish this. However, prepare the soil itself first before building columns beneath the floor joists. What they carry out:

  • cut off the fertile layer inside the foundation structure;
  • level it and compact it;
  • covered with crushed stone or sand, someone makes a concrete screed or rolls up asphalt.

The primary goal is to ensure that there is no moisture beneath the floor base and that no vegetation develops.

Subsequently, the supports are elevated or filled into the ready-made and erected formwork. The table is used to determine the spacing between the columns. It is crucial to treat or cover the upper plane, preventing the logs from coming into contact with any moisture, and to waterproof the supports from below as well as the sides.

If the columns are put together using separate building materials, such as stone, brick, or concrete blocks, a thin layer of foundation is poured beneath each support. This can take the form of multiple foundation structures for every support post or a single, strong foundation structure that serves as a tape for everything at once.

Lay the joists after all of the support columns are prepared. Here, the primary goal is to align them as precisely as possible in both the horizontal and vertical directions.

By foundation

This option and the previous one are essentially the same. To put it simply, the ends of each lag are laid on the house’s foundation. It is important to realize that, as previously mentioned, the parameters of the lumber used will depend on the span’s length. Additionally, thicker timber will need to be used for larger spans. However, this might not even prevent it from sagging.

The same approach used in the "on-the-ground" technology is used to solve the issue. In other words, employing columns.

By floor slab

Although many prefer to fill the floors with screeds and then lay a topcoat on top in the form of laminate, carpet, linoleum, or tiles, wooden floors can also be arranged along joists over a concrete base. Of course, it’s less expensive and easier. However, there are no limitations on installing wooden floors in the home if that’s what someone prefers.

However, bear in mind that logs lower ceiling heights, so in this instance, you can use smaller lumber by building small-pitched beams. This is precisely what skilled artisans accomplish.

Leveling the ceiling is a prerequisite for installing floor joists. This can be achieved with a screed that is slightly thicker. After that, the so-called zero level needs to be set. In other words, measure the height of the planned board floor. A laser level will be useful here.

Let’s now address the issue of how to fasten logs to a concrete foundation.

Attaching joists to a concrete base

There are numerous choices. Let’s examine each.

Thus, the simplest step is to place the logs on the concrete floor, level them with the same laser level, and fasten them to the ground with dowels or self-tapping screws. This involves using a puncher to create holes in the joists and floor every one to one and a half inches, into which plastic dowels for self-tapping screws are driven. After being positioned, the beams are screwed into position. In case a steel dowel is utilized, it is supposed to be put into the holes and its upper nut secured.

Using wooden bosses is the second method. These are essentially tiny fragments of the same wood intended for lags. Like with the logs in the previous instance, they are simply placed in pairs on the floor and fastened. The logs themselves are placed into the space that is left between the two bosses. Conveniently, the mounted beams can be easily raised or lowered, and they can be horizontally aligned at the desired height. Next, self-tapping screws are used on both sides to secure the logs to the bosses.

The third design option is referred to as self-leveling. In order to accomplish this, you will need to buy extra special tools that will allow you to move the logs up or down in a vertical direction in addition to attaching them to the concrete base. These are steel studs, if you would like, that are driven into the concrete floor at one end and have a nut and washer placed on top of them. Even a beam is installed on the projecting pin, in which a previously made through hole has a diameter that is marginally greater than the diameter of the pin.

The washer and nut support the jog. After that, the nut is screwed on after another washer is positioned on top of the beam. The lumber is secured in the desired location using two nuts. Simultaneously, the installation height of the beams can be adjusted by turning the nuts.

Not only can you use studs, but other devices as well. There shouldn’t be any issues with selection because there are plenty of self-regulating components available.

Therefore, three methods of installing wooden logs were examined. Craftsmen use all of them nowadays, but the self-leveling option is preferred more frequently because it makes the task of leveling the timber used easier.

Selecting the appropriate floor joists is essential for any building or remodeling project. These structural components are necessary to guarantee a sturdy and safe building because they bear the weight of the floor and everything on it. Choosing floor joists involves taking into account a few things.

First, take into account the joists’ span, or the distance they must span without the need for extra support. In order to avoid sagging or other structural problems over time, longer spans require thicker or stronger joists. The maximum spans for various joist types are frequently specified by building codes, guaranteeing adherence to safety regulations.

The ability of the floor joists to support a given load is another important consideration. The type of materials used, such as steel or laminated veneer lumber (LVL), or engineered products, will determine this capacity. Determining the appropriate strength required requires an understanding of the expected load, which includes both live loads (the weight of people and furniture) and dead loads (the weight of the structure itself).

Furthermore, the overall stability and functionality of the floor system are impacted by the distance between floor joists. More support and a decreased chance of sagging or flexing are provided by closer spacing, which is especially beneficial in larger spaces or places with heavy furniture. The installation of subflooring and other finishing materials is also made easier with adequate spacing.

Finally, take into account environmental elements like humidity and moisture content, especially in basements and other damp areas. Selecting materials that can withstand moisture or treating wood joists can help them last longer and retain their structural integrity over time.

Video on the topic

Beams and logs. Useful and reliable advice.

Construction and assembly of plywood floors on joists

✅ FLOOR INSULATION. Step-by-step instruction.

Proper flooring in a wooden house

IDEAL AND WORST FLOORING! / Which floor is better to make in the house?

What factor is most important for you when choosing materials for building a house??
Share to friends
Fedor Pavlov

Interior designer, author of books on residential design. I will help you make your home not only functional, but also beautiful.

Rate author
StroyArsenal62.com
Add a comment