Construction of a wooden floor on joists: diagrams, construction features, expert advice

Wooden floors on joists are one of the oldest methods of flooring and the only one used in the northern regions of our country. Modern materials have only improved ancient technologies, due to which the scope of applications has significantly expanded and performance indicators have improved. Before proceeding directly to the consideration of various options, you should familiarize yourself a little with the engineering requirements for calculations.

Installation of wooden floors on joists

Reasons for the popularity of log structures

Briefly about lags

Logs are transverse or longitudinal beams laid on concrete. Floorboards are attached to them, resulting in a floor that is level on a horizontal plane, which can differ only in the way the beams are fixed.

Laying joists on a concrete floor allows you to:

• create a flat surface for a wooden floor.
• transfer the load evenly to the load-bearing elements of the building (walls or foundation).
• leave a void between the base and the floor covering. Thanks to this, it is possible to well insulate the floor, protect the room from noise and lay various communications in the floor.

Types of flooring

The underlay is a material that is used as an additional layer between the base and the finished floor.
Today, the market offers a huge number of different types of flooring, for every taste, color and budget. And what’s interesting is that the development of innovative technologies contributes to the emergence of new, increasingly high-quality and practical varieties. So, when you visit a construction market, you will have plenty to choose from.

The most popular types of floor coverings include:

• laminate;
• parquet board;
• linoleum;
• massive board;
• ceramic tiles;
• carpet;
• A backing is also required for wooden joists.

Having a floor covering is, of course, good, but the quality and practical characteristics of floors can be made even better. To do this you need to use a substrate. The underlay is a material that is used as an additional layer between the base and the finished floor.

What material is used for joists?

Logs are made from a variety of materials (reinforced concrete, iron, plastic), but the most popular of them for many centuries has been wood. Iron channels and reinforced concrete elements are rarely used. High-strength logs can significantly increase the load-bearing capacity of the floor. More often, such elements are installed in industrial buildings. Wooden logs are the most common, so you need to disassemble them in detail.

They come in the form:

• square or rectangular beams;
• stacked and tied boards;
• adjustable lags.

Video example of the work

It is not very easy to construct a multi-layer floor pie on wooden joists, but it is precisely this that significantly reduces the construction or repair budget. In addition to minimizing material consumption, the pace of finishing production is also increased. Thorough adherence to the technologies for arranging this floor construction scheme and compliance with the recommendations guarantees long-term operation and aesthetic appeal.

Author: Alesya_SAPrint

Sources:

• www.supersadovnik.ru
• www.laser-level.ru
• 1poderevu.ru
• pol-master.com

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What should the cross section of the log be?

The strength of this part of the floor depends on the material of manufacture and the accuracy of load calculations. When choosing the size of the timber, the maximum permissible load on the floor is taken as a basis. For living rooms, this figure is 300 kg per 1 m2. For non-residential premises it is individual in each specific case, so before purchasing the material you need to calculate this indicator.

Basically, timber with a profile aspect ratio of 1.5 x 2 is laid under the floorboard.

The height of the beams must also be selected taking into account the thickness of the insulation. If iron and concrete elements are installed, their cross-section may be smaller. This is due to the fact that these materials are able to withstand high loads for a long time.

Spacer wedges for doors: technology of use

Another area in which these elements are actively used is the installation of doors, and they are used for both interior and entrance structures. The only difference is the number of sides of the vestibule.

Entrance doors, which usually have four-sided blocks, if installed on spacer wedges, do not require additional screed preparation. But the required number of wedges is selected depending on the mass of the door frame to be worked with in a particular case. Based on this, small or medium elements are used.

Hollow honeycomb doors can get by with two blocks of medium-sized wedges. Heavier items will require larger wedges. However, this makes it easy to level complex structures that have significant weight. To do this, just use a pry bar to slightly raise the edge of the threshold, and then adjust it using a level and install the block correctly. If everything is smooth and the support remains motionless, you can safely proceed to the final fixation.

It is advisable to use spacer wedges for installing interior and entrance doors.

Separately, it is worth mentioning how spacer wedges are used to adjust a door with a three-sided rebate. In this case, the installation of two leveling blocks is required - vertically on the box.

Step width between joists

The pitch between the joists is selected taking into account the thickness of the floorboard. The thicker it is, the larger the step between the bars is allowed. In addition, a thick board sag less under loads.

The table below allows you to quickly select the distances between the bars.

You can also resort to the following rule: when the width of the logs increases by 5 mm, their pitch increases by 10 cm.

When installing plywood, the cross-section of the joist is calculated differently. This is due to the fact that it has great bending strength. With a thickness of sheet material of 1.5-1.8 cm, it is fashionable to place logs against each other at a distance of up to 40 cm. It is necessary to install the beams so that the sheets are fixed at the edges and in the middle. Moreover, the edges of the sheets should fit half the width of the beam.

Tools

To install the beams, the following tools are required:

• electric drill or hammer drill;
• screwdrivers or screwdriver;
• electric circular saw or simple hacksaw for wood;
• plane;
• hammer;
• tape measure and level;
• fasteners.

Other tools may be required.

Base made of concrete and reinforced concrete (laying on an uneven base)

Before installing the logs, the uneven concrete floor is leveled with a cement screed. This technology allows you to make a smooth and reliable base for parquet, laminate or floor tiles, as well as well insulate the floor and protect the room from external noise.

For most floor coverings, a spacing between joists of 60 cm is suitable, but floor tiles require cells measuring 30x30 cm because they are very fragile.

Reinforcing mesh in the screed and spacers between the beams increase the rigidity of the floor. Thermal insulation material can be placed in the resulting cells.

Fixation methods

Basically, four fastening methods are used to fix joists on a concrete floor. Therefore, if you do not know how to attach joists to a concrete floor, then after studying all these methods you will understand this issue.

Fixation with self-tapping screws

This method is considered simple, but it is not suitable for all cases.

1. First you need to prepare the concrete surface. To do this, it is cleared of debris (it is allowed to use a vacuum cleaner). Then they repair cracks, chips and other defects with cement mortar or polyurethane foam.
2. Next, in the logs (treated with antiseptics) you need to drill holes with a drill to install plastic dowels. Then you need to drill counter holes in the concrete using a hammer drill.
3. Then the dowels are driven into the concrete with hammer blows, and then self-tapping screws are screwed into them with a screwdriver. Moreover, the head of the screw is driven into the hole 2-3 cm.

Fixation with anchors

Anchors securely fix the beams to the concrete, so this method is the most reliable. In addition, such fasteners help to restrain the deformation of wooden logs if they are not dried well. But the boards laid on them can sag, so it is necessary to install spacers more often.

1. First, you also need to prepare the concrete floor (remove debris from it and repair all defects with mortar).
2. After which it is necessary to make through holes in the timber (treated with antiseptics) with an electric drill.
3. Next, you need to drill holes in the concrete opposite each hole with a hammer drill.
4. Then the anchors are mounted on a concrete base and tightened with keys. The main thing here is not to overtighten the bolt, because this will cause the beam to bend. This is especially true for those places where there is a gap.

Before installing the anchors, trenches (small recesses) are made in the joists to hide the bolt heads.

Anchors need to be installed every 600-1000 mm. This distance is selected taking into account the partial immersion of the anchors in concrete (approximately 60 mm). Many people fix the beams to the concrete with 4-5 anchors ⌀ 10 mm.

Fixation with iron corners

It is difficult to work with high logs (100 mm and above), so they are fixed to the concrete with iron corners. One shelf is attached to the beams with self-tapping screws, and the other is fixed to the concrete with dowels and nails. The main thing is that the entire load goes to the spacers, and not to the corners, since their main function is to fix the position of the beam.

1. First, screw the corner to the joists with self-tapping screws, which need to be deepened into the wood by 3 cm.
2. Next, it should be fixed in concrete with dowels.

Adjustable joists

This fastening of the joists to the concrete floor involves the installation of rectangular supports under the beams, which are secured to the base with the help of four dowels. In the center of this fastener there is a pin that secures the joist to the concrete. The nuts placed under the beams allow you to accurately set the height of the logs, and the nuts located on top allow you to reliably fix their position. The pitch of supports installed under the beams depends on the size of the profile of the beams, but experts advise not to make it longer than 1 m. This type of floor sheathing fastening is not in demand due to its high cost.

Mounting plastic wedges: technical characteristics, advantages and disadvantages

It was previously mentioned that completely different elements can be used as homemade spacers. These can be either wooden or metal products of suitable size. This solution has a serious drawback: wood can react negatively not only to high humidity, but also to dryness. Drying and swelling of a homemade wedge can reduce all efforts to zero. In addition, wood is a breeding ground for insects and microorganisms.

Naturally, choosing a wooden element of the right size may require a lot of time and effort. This is not a very practical solution, especially if we are talking about a full repair, and not about selecting one sample.

The main technical advantage of parts specially designed for such purposes is not this. The plastic spacer wedge, if selected correctly, does not deform even after time. But wood often sags. The result is warped windows and doors, and gaps in the floor.

The main advantage of plastic wedges is that they do not deform over time.

Among other positive characteristics of these parts, it is worth noting the following:

All these characteristics allow us to rightfully consider plastic mounting wedges the most correct and practical solution when it comes to the need to level the surface. Their cost allows you to give up thinking about saving, so you don’t need to make elements of the appropriate size yourself.

Fixation to concrete pillars

This method involves fixing beams to concrete pillars, using similar fasteners, but designed specifically for pillars.

1. The pillars must be covered in advance with a waterproofing layer (bitumen or mastic is used). Their upper part can be protected from moisture with roofing felt. You need to pre-drill holes in the posts and beams.
2. Next, you need to drive dowels or anchor spacers into them.
3. Then the beam is attached to the post with self-tapping screws 2-3 times longer than the width of the spacer.
4. The timber is attached to the posts using iron plates with screws. They are fixed to the posts with dowels-nails, and to the beams with screws.

Thanks to the study of all these fastening methods, the question of how to install joists on a concrete floor disappears by itself.

Geometric guidelines for installation

Orientation in space is a significant component of the correct floor arrangement. Those who want to know how to lay joists on the floor correctly should follow the following building rules.

The flooring of boards in rest rooms and living rooms is carried out along the direction of the flow of natural light. The logs are arranged “cross” to the direction of the boards. In vestibules, hallways and other rooms with heavy traffic, the boards are laid according to the direction of movement, the logs, naturally, in the direction perpendicular to the direction of the flooring elements.

The logs are laid “cross” to the floor boards

Note. If the floor structure is strengthened by installing two layers of timber, the top layer is laid “cross” to the previous one.

Installation process and features

Properly selected building materials are the key to successful floor installation. Logs are mainly made from wood of various species, with a moisture content of no more than 18%. After purchasing the bars, you need to let them acclimatize to room temperature for several days. The logs bent during this time are rejected. Before laying, they are treated with an antiseptic composition to prevent mold and pests from appearing on them.

1. Preparing the concrete base. It is cleared of debris, cracks are sealed and irregularities are removed.
2. The tree must be protected from moisture. Therefore, the beams are covered with rolled waterproofing materials, mastics and treated with impregnating compounds.
3. It is necessary to prepare all the fasteners and substrates required for installation of the joists on the concrete floor. They must have high rigidity so that they do not sag under loads and gaps do not appear between the joists and the base. Thin boards, plywood and plastic substrates, which are sold in specialized stores, are suitable for this. They are slipped under the joists and securely fixed.
4. The logs must be placed across the light coming from the windows. Wood often becomes deformed due to temperature changes, but thanks to this installation it heats up evenly. In rooms without windows, the bars must be placed across the direction of movement.
5. The pitch of the beams is selected based on the thickness of the floorboard. In this case, the rule is used: the thicker the board, the larger the step between the lags can be chosen. On average, it varies in the range of 40-50 cm. The logs located near the walls are installed 20-30 mm from the wall, and the rest, taking into account the dimensions of the room.
6. After assembling the grating under the floor, it must be accurately installed horizontally. The support for the floor must be perfectly level, so many experts level the floor with a screed if the height of the room is sufficient for this. The underlay for the joists also allows you to level the floor.
7. For good shock absorption and increased protection from moisture, logs are placed on roofing felt and other similar materials. These materials should not be soft, because they will sag under the influence of loads, which will lead to the formation of gaps. As a result, the floor will creak while walking.

What are mounting wedges

Preliminary leveling is rarely complete without all kinds of substrates, wood chips or bars. Using improvised materials is cheap and cheerful, but not always convenient; you have to carefully select the thickness and number of substrates, which over time can dry out and form sediment.

Plastic mounting wedges do not have these disadvantages. Despite their primitive appearance, these devices are an example of well-thought-out engineering. The wedges are made of plastic, the service life of which is no less than that of the mounted elements.

The wedge has a cross-section in the shape of a right triangle, the legs of which are the nominal length and height. The surface of the wide edges is ribbed, and the shape of the protrusions is specially selected so that the two folded wedges do not move apart under load. This is exactly how they are used: at least two wedges form a rectangular leveling block, which does not distort the shape of the supporting surface and can be easily adjusted in height by bringing the wedges together and apart.

Insulation and sound insulation

Soundproofing and insulating floors on beams is quite simple. For example, you can cut TECHNONICOL into strips and lay it between the beams. In this case, the self-adhesive side section that overlaps the beam must be rolled with a roller. For additional insulation of the floor, you can place mineral wool on top of the TECHNONICOL. This sound insulation allows you to protect your living space from noisy neighbors downstairs.

The height should not exceed the bars. In those places where it is higher than the log, its thickness must be reduced. To do this, the cotton wool needs to be cut lengthwise with a knife. If the result is rags, this will not affect the properties of the material.

Further floor arrangement

Further installation of the floor along the joists involves two more stages of work.

The first stage is laying the finished floor

After installing the logs, thermal insulation, waterproofing and sound insulation, the finished floor is laid. They begin to lay it from the corner of the room. The first row of boards is placed tongue-and-groove against the wall, with a gap of 10 mm between the wall and the boards. This will compensate for the deformation of wood that appears from temperature changes and changes in humidity levels.

The next row is placed offset to the previous one by approximately 2 lags. To lay the boards tightly, apply a piece of wood to the ends of the board being attached and hit it with a hammer.

The boards are fastened to the joists with screws, the heads of which are driven into the boards.

After laying the boards, the expansion joints are covered with plinths.

Expert advice:

• lay the floor on a concrete base after leveling all the joists along the horizontal plane;
• boards must be attached to all beams;
• their size is chosen so that the joints between them are in the middle of the lag.
• To prevent them from cracking, it is necessary to make small-diameter holes in them for self-tapping screws. For the screw head it is necessary to make a countersunk hole, for drilling which you need to use a drill of a larger diameter.
• Instead of a plinth, you can install profiled strips - fillets.
• holes for pipes need to be made 8-10 mm larger.

To increase the accuracy of installation, experts advise that before fastening the boards, tighten them together with the staples of a construction stapler.

The second stage is the final finishing of the floor

This is the most critical stage of work on arranging a floor on a concrete base on joists. The appearance of the floor and room depends on the choice of finishing material. Listed below are the main types of final floor finishing.

Parquet

Parquet consists of solid wooden planks from which the floor covering is laid. It makes the floor very attractive. This flooring has a long service life - more than 30 years. In addition, part of the parquet can be replaced at any time.

Laying parquet requires a lot of experience, so it is difficult for an ordinary person to lay it falsely, since the technology for laying parquet is complex and labor-intensive. In addition, this coating is expensive. During operation, parquet requires careful handling, as it is scratched and afraid of moisture. To keep this floor always beautiful, it must be regularly polished and varnished.

Linoleum

This floor finish is very popular today. This is due to the low cost, practicality and ease of installation of this flooring material. You can lay linoleum indoors yourself, because this does not require special knowledge and skills. A floor covered with linoleum is resistant to moisture and aggressive liquids, while it looks beautiful.

Linoleum is easy to clean and sweep. Thanks to the wide variety of textures and colors, it can be matched to almost any color of furniture and wallpaper.

Linoleum can be laid on top of boards, plywood or concrete. Thick linoleum with a base of more than 3 mm can hide small unevenness in the floor and seams of sheet materials.

The disadvantage of linoleum is its low maintainability. If a hole appears on it, then it will not be possible to seal it and make this place invisible.

Laminate

This flooring is quite expensive. In appearance and performance characteristics, this material is similar to parquet. It is easy to install and does not require special care. The choice of laminate on the finishing materials market is quite extensive, so everyone can choose the option that suits them.

Laminate is very susceptible to moisture. In terms of price, it is comparable to the cost of high-quality linoleum, but it can be 3 to 7 times more expensive. Laminate floors look elegant.

Fiberboard

Fiberboard is rarely used today for finishing floors. This material is mainly used to level the floor for the installation of other floor coverings. The sheets are secured to the floor with small nails or self-tapping screws. After fixing, the fiberboard is painted in 2–3 layers. This material is also afraid of moisture, because it swells under its influence.

Carpet

This floor covering looks beautiful and additionally insulates the floor. At the same time, carpet quickly loses its attractiveness (the pile wears out and gets worn out), which is why it is used only in bedrooms and children's rooms, where people rarely walk.

It is difficult to clean and quickly absorbs moisture. Drying the carpet without dismantling it is extremely difficult. In terms of installation, the material is convenient; it is simply rolled out on the floor and trimmed where needed.