How to calculate the timber for building a house

Recommendation points

• The benefits and harms of calculation programs
• Manual calculation of timber content in walls: basic methodology
• Accounting for openings
• Determination of the optimal molding
• Liquidity of cut residues
• Corrections for marriage and vices
• Calculation of crown insulation and dowels

The vast majority of construction projects require preliminary design, and for timber houses it is strictly necessary. One of the integral components of such a project is the calculation of the consumption of building materials, we will consider this issue today.

The benefits and harms of calculation programs

Every novice builder can use free software for calculating timber for building a house, including numerous online services. All that needs to be indicated to the program is the linear dimensions and height of the walls, as well as the assortment of the timber planned for use. The result of the program is the cubic meter of timber, which must be delivered to the facility in order to start construction.

The algorithm of work of such software is simple: the volume of the walls is simply calculated. For a truly correct calculation, this is not enough: the molding of lumber, allowances for splicing and bandaging, liquidity of edged residues and a number of other factors are not taken into account. When building a log house from a rounded beam, the error goes beyond all reasonable limits.

An example of an online calculator for calculating the amount of timber for a house

You can take the path of least resistance: make a preliminary calculation using a calculator, add a margin of 7-10% to the resulting value and build a box from what is, adding a few more crowns during aging. The maximum that a developer can “get” on with this option is a repeated payment of transport costs and a slight increase in construction time.

We propose to consider a calculation option, which will take into account the consumption of materials for construction up to the last dowel. As a result, you will receive not only a report on the volume of purchases of mixed timber and assortment, but you will also be able to ensure the minimum number of splices and receive initial data for an independent compilation of a full-fledged construction project and a list of parts for a log house.

Manual calculation of timber content in walls: basic methodology

The calculation of the timber for construction begins with the fact that the plan of the future box is drawn on paper, and then laid out into a number of linear sections. It should be understood, however, that the actual length of the walls may be greater than the planned length when cutting “into a bowl”.

For each of the walls of such a layout, you need to specify three key parameters: length, height and thickness. When determining the length, it is necessary to additionally take into account the protrusions of the dressing, which are 1–1.5 thickness values, for the height – the shrinkage value (from 3 to 7%). The thickness of the timber is determined according to a more complex scheme. For enclosing walls, it is selected based on the desired heat-saving characteristics, but not less than 150 mm. At cross-sections, installed every 6-9 meters, depending on the thickness of the timber, the nominal thickness of the outer walls should be adhered to. Internal partitions can be of arbitrary thickness, but usually not less than 100 mm for correct installation of interior doors.

The first thing when calculating the timber for the external walls is to determine the total number of crowns, which is done by dividing the height by the thickness of the frame. Next comes the most interesting part of the problem: calculate the total length of the timber in all rims and find a compromise solution on the length of the molding in order to:

1. The total length was a multiple of the length of the beam used, or the remainder of the division was at least half the length of the molding.
2. Each crown had the minimum possible number of splices.

For example: on a wall 7.5 meters high with 18 crowns, it makes no sense to use an 8-meter timber, otherwise 18 scraps of 0.5 meters each with a high probability will not be used rationally. If you use a 6-meter bar in the amount of 23 pieces, you will end up with a layout scheme in which no more than one splicing will be required for each crown, each of which will be shifted relative to adjacent rows by 1.5 meters. As a result, there will be a 3-meter residue, the length of which allows it to be reused on other walls.

Accounting for openings

The described calculation scheme is quite simple, but the presence of window and door openings in the walls can make its own adjustments. To reduce unaccounted cuttings, it makes sense to display each of the walls with openings schematically. From the previous example, we remember that when choosing a molding of 8 meters, there were many short cuttings left. If there is an opening on one of the walls located closer than 0.5 meters to its edge, these trims can be successfully applied.

Also, when placing openings, it should be borne in mind that their top should be closed with a solid piece of timber, overlapping the pillars of the walls of the order of 3-4 values ​​of thickness. Therefore, walls with openings are divided into zones for calculation:

1. The area above the openings is calculated as a separate low wall, taking into account the above-described requirement for the length of the lintels.
2. Area in the area of ​​openings – a place for the application of trim residues.
3. In the area under the window openings, it is allowed to place splices directly in the cross-section of the openings, therefore, the layout of the beam here is performed according to a freer scheme.

Determination of the optimal molding

A beam for building a house is made on sawmills on an individual order, because the use of the most common molding of 6 meters will not always be successful. At the same time, the more “homogeneous” the order is, that is, the fewer beams of different lengths and thicknesses in it, the easier it is to make sawn timber using it and, accordingly, it is easier to cut the parts of the log house on site.

If you have at your disposal schematic sketches of each of the walls, you will be able to process several layout options in a short time. In this case, calculations begin with the shortest walls without openings, marking the scraps in the list of residues. After that, these remnants are tried on to other walls. After going through about 3-4 options with a difference in the length of the used timber of about 1 meter, you can come to the most optimal length of the supplied timber.

As you draw up the layout maps, you may find it much easier to pre-order bars of different lengths. The likelihood of such a decision depends on the correctness of the shape of the building. The higher the difference between the length of the enclosing walls, the more the house has protrusions and deviations from the rectangular plan – the more undercuts will be required, which means that at least some of them are quite reasonable to be performed immediately in the sawing shop.

Liquidity of cut residues

As you lay out the layout, the number of scraps can make a very impressive list, which is easy to get confused. The solution to the problem in this case is an ordinary spreadsheet of residues. It can have only two columns: the size of the segment and the number of residues of this size. You can add a third column to the table with notes in the form of the code of the part used, the corresponding annotations can also be made on wall layout maps.

It is very simple to work with the table: when drawing up a diagram of the distribution of each wall, you are faced with the need to fill a gap that is inferior in length to the available molding. Instead of using a solid bar and entering another remainder into the table, you check for the presence of segments in the required length range. If there is no corresponding remainder, you can use a larger one, respectively, an entry appears in the table about another, already shorter trim.

When choosing the permissible length of the segments, one should also be guided by the general rules for building a log house. So, remnants of 1.5–2 meters in length can be quite successfully used in ordinary masonry, while meter and shorter beams will require an increased pitch of installation of dowels. However, “short ones” can be used to strengthen the walls with a significant step of the cut or, as already mentioned, when forming openings.

Corrections for marriage and vices

Enumerate manually 30-40 m³ timber for quality is not a quick and tedious task. If you value your time or simply do not know how to visually determine the quality of wood, but want to build a strong and durable house – provide a stock when ordering material.

Even professional cutters lay in 2-3% of additional lumber: the timber is always useful on the farm, and it is much easier to close the purely statistical shortage in advance, so as not to pay again for freight transport services. In this case, you need to “throw” the stock individually for each group with a certain molding, rounding the number of logs always upwards.

An example of wood defects: 1 – rot; 2 – crack; 3 – wormholes; 4 – fungal infection; 5 – sprout; 6 – group knot

The indicated size of the material reserve takes into account the identification of defects that cannot be determined by external signs: xylem rot, sapwood delamination, delamination, wormholes, flawless and apex cracks, hollow cores and other defects developing in a separate section of the trunk. The probability of detecting such a marriage is the higher, the longer the length of the timber, and the initial quality of the forest also plays a significant role. Therefore, it will not be superfluous to first make inquiries with other customers of the selected supplier..

Calculation of crown insulation and dowels

The calculation of materials for a house from a bar is not limited to wood alone. It is necessary to additionally purchase the required amount of insulation and thin bars or round timber, from which the pins will subsequently be made.

The spacer seal is calculated very simply: you have the total length of the walls and their thickness, respectively, it will not be a problem to determine the area of ​​the horizontal section. Knowing the number of crowns, you can order any of the types of insulation:

1. Felt or jute canvases – according to the total cross-sectional area.
2. Strip seals – along the total length of the walls.
3. Stuffed seal – by the volume of the grooves multiplied by their total length.

The fastening spikes are also easy to calculate. Usually they are taken with a significant margin: the risk of damage to the thorn during driving is quite high, and the total volume of lumber used for their manufacture is relatively small. Therefore, you should not save “on matches”: in addition to the obligatory ordinary spikes every 1.2-1.5 meters and corner dowels for each notch, two dowels should be provided for each rallying, adding an additional 5-8% to the amount received.