Gable roof calculator. Do-it-yourself rafters for a gable roof: design and installation. Minimum section of rafters, Weight and Volume of timber for rafters
Take advantage online calculator ohm gable roof to calculate the number of crates, the angle of inclination truss system, loads (wind and snow) on the roof. Our free calculator will help you calculate the amount of material needed for of this type roofs.
Specify roofing material:
Select a material from the list -- Slate (corrugated asbestos-cement sheets): Medium profile (11 kg/m2) Slate (corrugated asbestos-cement sheets): Reinforced profile (13 kg/m2) Corrugated cellulose-bitumen sheets (6 kg/m2) Bituminous (soft , flexible) tiles (15 kg/m2) Galvanized sheet (6.5 kg/m2) Sheet steel (8 kg/m2) Ceramic tiles (50 kg/m2) Cement-sand tiles (70 kg/m2) Metal tiles, corrugated board (5 kg/m2) Keramoplast (5.5 kg/m2) Seam roof (6 kg/m2) Polymer-sand tile (25 kg/m2) Ondulin (Euro slate) (4 kg/m2) Composite tile (7 kg/m2) ) Natural slate (40 kg/m2) Specify the weight of 1 square meter of coating (? kg/m2)
kg/m2
Enter roof parameters:
Base Width A (cm)
Base length D (cm)
Lift height B (cm)
Length of side overhangs C (cm)
Front and rear overhang length E (cm)
Rafter:
Rafter pitch (cm)
Type of wood for rafters (cm)
Working section of the side rafter (optional) (cm)
Lathing calculation:
Purlin board width (cm)
Lathing board thickness (cm)
Distance between decking boards
F(cm)
Snow load calculation:
Select your region using the map below
1 (80/56 kg/m2) 2 (120/84 kg/m2) 3 (180/126 kg/m2) 4 (240/168 kg/m2) 5 (320/224 kg/m2) 6 (400/280 kg/m2) 7 (480/336 kg/m2) 8 (560/392 kg/m2)
Wind load calculation:
Ia I II III IV V VI VII
Height to building ridge
5 m from 5 m to 10 m from 10 m
Terrain type
Open area Closed area Urban areas
Calculation results
Roof pitch: 0 degrees.
Tilt angle suitable for this material.
The angle of inclination for this material is desirable to increase!
It is desirable to reduce the angle of inclination for this material!
Roof surface area: 0 m2.
Approximate weight roofing material: 0 kg.
Number of rolls insulating material with an overlap of 10% (1×15 m): 0 rolls.
Rafter:
Load on the truss system: 0 kg/m2.
Rafter length: 0 cm
Number of rafters: 0 pcs
Lathing:
Number of rows of lathing (for the entire roof): 0 rows.
Uniform distance between the boards of the crate: 0 cm
The number of boards of the crate with a standard length of 6 meters: 0 pcs
Volume of boards of an obreshetka: 0 m 3 .
Approximate weight of batten boards: 0 kg.
About the calculator
The online calculator for a gable roof, also called a gable roof, will help you calculate the desired angle of inclination of the slopes, determine the cross section and number of rafters, the amount of materials per sheathing, the consumption of insulating materials, and at the same time take into account existing standards for wind and snow loads. You don't have to do extra additional calculations, because in this calculator there is most of the existing roofing materials. You can easily calculate the consumption and weight of such common materials as shingles, cement-sand and ceramic tiles, metal tiles, bituminous and asbestos-cement slate, ondulin and others. If you use a non-standard material, or want to get more accurate calculations, you can specify the mass of your own roofing material by selecting the appropriate item in the drop-down list of materials.
Note!
The calculator makes calculations in accordance with the current SNiP "Loads and Impacts" and TCP 45-5.05-146-2009.
A gable roof (there are variants of the name "gable roof" and "gable roof") - the most common type of roof, in which there are two inclined slopes from the ridge to the outer walls of the structure. The popularity of this type of roofs is explained by their moderate cost, ease of construction, good performance and attractive appearance.
In this design, the rafters of different slopes lean against each other in pairs and are sheathed with sheathing boards. The end of a building with a gable roof has a triangular shape and is called a pediment (the name “tongue” is also found). Usually located under the roof slopes attic space, naturally lit by small window openings located at the top of the gables.
When filling out the fields of the calculator, you can find out Additional information located under the sign.
For any questions or ideas regarding this calculator, you can write to us using the form at the bottom of the page. We will be glad to hear your opinion.
Additional information about the calculation results
Roof slope
At this angle, the slope and rafters are inclined to the base of the roof. Roofing materials have individual limiting roof slope angles, so some materials may have an angle outside allowable norms. Whether your angle satisfies the selected material or not - you will find out in the calculation results. In any case, it is always possible to adjust the height of the roof (B) or the width of the base (A), or choose a different roofing material.
Roof surface area
The area of the entire roof surface, including overhangs. To determine the area of one slope, it is enough to divide the resulting value by two.
Approximate weight of roofing material
The weight of the selected roofing material from the calculation total area roofs (including overhangs).
Number of rolls of insulating material
The amount of insulation material required to build a roof. The quantity indicated in rolls is required for the entire roof area. The standard roll is taken as a basis - 15 meters long, 1 meter wide. The calculation also takes into account an overlap of 10% at the joints.
Load on the truss system
The maximum weight per truss system. Wind and snow loads, the angle of inclination of the roof, as well as the weight of the entire structure are taken into account.
Rafter length
The full length of the rafters from the roof ridge to the edge of the slope.
Number of rafters
The total number of rafters required for a rafter system at a given pitch.
Minimum cross-section of rafters / Weight of rafters / Timber volume
- The first column shows the sections of the rafters according to GOST 24454-80 Lumber conifers . Here are the sections that can be used in the construction of a given structure. The calculator proceeds from the total loads that can affect the structure of a given roof and selects the cross-sections that satisfy them.
- The second column shows the total weight of all rafters with the specified section, if they are used to build a given roof.
- The third column shows the total volume of this timber in cubic meters. This amount will be useful to you when calculating the cost.
Number of rows of battens
The number of rows of lathing that will be needed for the entire roof with the given parameters. To calculate the number of rows of crates of one slope, you need to divide the resulting value by two.
Uniform spacing between boards
The volume of boards of the crate
The total volume of the crate for a given roof. Given value will help you calculate the cost of lumber.
The strength of the roof of the building depends on how correctly the calculation of the rafters is performed. In this design, all parameters are important: length, angle of inclination of the roof, section of the beams.
Factors to consider when calculating
The calculation of the section of the rafters and their length is carried out in several stages. At the first stage, the snow and wind load is calculated for the selected roof configuration, taking into account correction factors for the building height and slope angle.
Then the load from the weight of the roofing material, insulation and battens is added. 10% is added to the resulting total load for a margin of safety. The final value is used to calculate the rafters.
It is quite difficult to perform a competent calculation if you do not take into account the strength and frequency of the loads exerted on them.
Factors affecting the roof are divided into three groups:
- permanent loads;
- variable loads;
- special loads.
Constant loads act on structural elements without ceasing, regardless of the seasons.
These include the mass of the roof, waterproofing, lathing, vapor barrier, thermal insulation and all individual parts of the roof that have a constant weight and exert pressure on the truss system.
Weight of single or gable roof increases when massive devices and devices are installed on it - antennas, ventilation, snow retainers, etc.
A strong influence on the strength of the rafters of a shed and gable roof is exerted by the weight of the snow layer, the wind blowing and the workers climbing the roof.
Such loads are called variable, since it has a periodic nature - strong pressure is replaced by its absence.
A special type includes loads that occur in regions where hurricanes or earthquakes often occur.
With this type of load, an additional margin of safety is taken into account during the design and construction of buildings.
Calculation for roof rafters is a rather difficult task, a non-specialist may not be able to cope with it.
Calculation of the load on the rafters
The wind load is calculated in a simplified way as follows: multiply the regional indicator of wind load by correction factor. The regional indicator is taken from the SNiP according to the wind load map.
Correction factor for buildings in height:
- below five meters is taken in the range of 0.5 - 0.75;
- from five to ten meters - 0.65 - 1.0;
- from ten to twenty meters - 0.85 - 1.25.
A smaller value of the coefficient is used for built-up or wooded areas, where the force of the wind is pacified by obstacles, a larger value is taken for open areas.
In the event that the building is located on an open territory on at least one side, a larger range value is also applied.
The snow load is calculated in a similar way - the snow load index is multiplied by the correction factor.
The coefficient depends on the angle of the roof:
- a gentle slope with a slope of up to 25 degrees has a coefficient of 1.0;
- for a slope with an angle of inclination from 25 to 60 degrees, the coefficient is 0.7;
- if the slope angle exceeds 60 degrees, then the snow load is not taken into account.
The snow load indicator is indicated on the corresponding SNiP map similarly to the wind load map.
If the building is located close to the border of two regions, then the value for the region with the highest score is used.
The obtained values of wind and snow load are summed up. The final value obtained on this stage calculations, is called the indicator of variable loads.
The calculation of permanent loads acting on the truss system depends on the type of roof chosen.
Permanent loads are calculated for the roofing "pie" by adding the weight of its components - lathing, insulation, waterproofing, roofing material.
Weight of the most common roofing materials:
- cement-sand tiles: 20 - 30 kg per square meter;
- slate: 10 - 14 kg per square meter;
- shingles: 6 - 8 kg per square meter;
- metal tile: 3.5 - 4.5 kg per square meter;
- ondulin: 3 kg per square meter.
From the above data it follows that the static load may vary depending on the selected type of roofing material used.
Adding the values of static and variable loads and adding 10% for a margin of safety, we get the final value, which will be used for further calculation of the rafters.
Calculation of the size and pitch of rafters for single-pitched and double-pitched roofs
For accurate calculation rafter system, there are specialized programs and online calculators.
However, for a simple shed and gable roof, the necessary parameters can be calculated independently without their help.
It should be noted that the rafter should protrude outward beyond the edge of the wall by at least 60 cm. The standard length of the rafter is 6 m. If necessary, by calculating the length, it can be increased.
The calculation of the step for the rafters should take into account the distance between them in the range of 60 - 100 cm. The greater the load, the more often it is necessary to install the rafters.
The total number of rafters per roof slope is equal to the length of the slope divided by the pitch of the rafters, plus one rafter. Accordingly, for a gable roof, this number must be doubled.
The less often the calculated pitch of the rafters, the wider the rafter beam. For load-bearing structures gable or pitched roof this size should be at least 15 cm for large buildings, and for suburban buildings(sheds, gazebos and baths) - 10 cm.
Then the number of rafters per slope is set. To do this, its length should be divided by the installation step. If the house is gable, then the resulting value should be doubled.
The choice of a suitable rafter section depends on the pitch of the rafters and their length:
| Rafter length, cm | Rafter pitch, cm | Rafter section, cm |
| Up to 600 | 140 | 10x20 |
| 100 | 8x20 | |
| Up to 400 | 180 | 9x18 |
| 140 | 8x18 | |
| 100 | 8x16 | |
| Up to 300 | 180 | 9x10 |
| 120 | 8x10 |
To reduce the deformation of rafters and beams during operation, it is best to use dry lumber for the rafter system.
When choosing beams for rafters, it is necessary to pay attention to the absence of cracks and knots.
In the most common case, for a gable roof of a one-story building covered with slate, it is advisable to use wooden rafter section 5x15 cm.
Varieties of roof structures
Before the beginning roofing works need to pick up best option roof structure. Each of them has its pros and cons.
Classification of truss systems:
- hanging;
- layered;
- hybrid.
If the roof standard width 6 m (respectively, such a leg length of the rafter), then fit hanging systems. By fixing the ends to the roof ridge and bearing wall fastening is made.
In addition, a tightening is installed that prevents deformation of the pressure and stress of the truss structure. In addition, they take on the role of load-bearing beams.
Inclined systems are suitable for roofs of any width. The fixation of the bed in relation to the Mauerlat ensures the stability and reliability of the entire structure.
As a result, the pressure is smoothed out by the rack, and the stress is reduced. The advantages of a layered truss system in enough simple installation, but the work will be costly, since additional lumber will be required to equip the beds.
Hybrid structures are most suitable for multi-pitch roofs, in which transitions are accompanied by numerous repeating beams, reinforcements, beams, posts, bevels and other elements that ensure the stability of the system.
The construction of a hybrid structure is expensive and quite difficult, therefore, qualified specialists should be involved in the development of the project and construction.
Seemingly simple at first glance, the question of calculating the rafters (their cross section, length, pitch and other parameters) actually requires a thorough and responsible approach.
It is not enough just to estimate the distance from the top outer wall buildings in order to buy the right amount of roofing lumber, because with this calculation you will have to constantly adjust the work.
To avoid problems during construction, it is necessary to take into account many important parameters: from the thickness and length of the beams to the area of the future roof.
Besides, great importance has the terrain and climate of the region in which construction is underway.
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The strength of the roof directly depends on how accurately the calculation of the truss system is made, in which both the angle of inclination of the slopes and the length, as well as the cross section of the beams, matter.
Choosing a truss structure
The strength of the roof is determined not only by the material from which the rafter legs are made, but also by the scheme of their assembly. For example, someone might decide that metal trusses would be the most reliable roofing solution, but be aware that this will create additional stress on the walls and foundation, which will have to be reinforced. Therefore, lumber is often used for rafters, among which timber, boards, and planks can be distinguished. different section for the crate. Rarely used round.
Wood is strong enough, but it is very important to measure the area of the roof with the length and cross section of the supporting elements. That is why the mauerlat (supporting horizontal beams along the upper edge of the walls along the entire perimeter of the house) is selected with large stock strength. In addition, all parts are sized to support their own total weight, including roofing and additional live loads (long-term or short-term). All this should be taken into account directly in the design of the house.
Regardless of the design, only certain elements are used in it, namely: rafter legs, racks, angled struts, ridge beam. Crossbars and girders are also needed, which provide rigidity to the roof frame. But since the fundamental factor is the area of \u200b\u200bthe roof and its slope, calculations are carried out only with respect to the rafters: their length, cross section and angle to the horizon, as well as the distance between them. It is known that the triangle resists loads best of all, therefore it is this figure that is formed with the help of crossbars installed as crossbars between the rafters of a gable roof.
All parameters must be specified in millimeters
B- The length of the roof.
Y- Height.
C- Overhang distance.
X- Roof width.
Y2- Additional height.
X2- Additional width.
This program will help you perform an accurate calculation of building materials for the construction of a roof: the number of rafters and sheathing boards, roofing material (roofing material, glassine), the amount sheet material(metal tile, slate, nulin or ondulin).
Our online calculator will calculate other useful roof sizes.
The presented program performs the calculation in two versions: type 1 - simple gable roofs, type 2 - gable roofs with 2 side gables.
If the projected roof has only one side pediment, then in this case we perform the calculation by type - 1, and then by type - 2. Based on the results of the calculations, you can determine the required amount of materials: roofing, sheet, rafters and sheathing board.
Otherwise, you will make an error in the calculation, since the program takes into account the cutouts for the side fronts when calculating the parameters of the main roof.
Based on the results of the calculation, you get the volume and size of the material for one roof slope, and the entire volume and size will be indicated in brackets.
When calculating volume and useful dimensions additional roof, you get two parameters in parentheses: the volume and size of one or two additional roofs.
Important! It is worth considering that the program performs a calculation over the entire area of the roof, when determining the number of sheets of roofing material.
For example, a row takes 7.7 sheets, and only 2.8 rows. Based on the results of the calculation, you will receive 3 real building rows.
In the event that you want to get the exact number of sheets for the future roofing, you need to reduce their height until you get an integer number of rows.
Do not forget to set the exact length of the overlap.
Important! In type 2 mode, when calculating the amount of material for the main roof rafters, the program does not take into account cutouts for side gables. This calculation of the gable roof truss system is associated with the design of the program itself.
Also, the remaining building material for the rafters, you can use to build or repair a house, otherwise you can make corrections to the calculations.
Accurate calculation approximate cost roof depends on the correct basic measurements.
Important! Do not forget to purchase building materials with a margin of 5-10% for waste.
Do-it-yourself gable roof
First of all, we need a diagram (drawing or design) of a gable roof, according to which we will perform all calculations (listed above).
The procedure for erecting a roof is quite simple, but the sequence of certain steps must be followed.
Before you install beams or transfers for future flooring, you need to determine whether an attic or just an attic space will be equipped. As a rule, for a simple attic, it is enough to choose a board 150x150 mm. In the event that you plan to build an attic, then it is best to choose a bar with the same size. To increase the strength of the frame, you should mount the bars or boards exclusively on the walls.
The process of fixing the beams is carried out taking into account the release from the outer edge by about 400 mm in order to prevent precipitation or wind from entering under the roof.
We will use a board edged under 50X150 mm when arranging the attic frame, and fixing is carried out with roofing nails. To give the gable roof stability, it is necessary to perform all measurements correctly, trying to eliminate the error.
Now we turn to the assembly of the truss structure, starting the installation from the gables, using the method already described above. At the same time, we saw off the lower parts of the boards, which will give our rafter structure additional stability.
When the structure is fully erected for a gable roof, we begin to cover with roofing materials.
Advantages of a gable roof:
- This design is quite simple to build, which allows you to perform all the work yourself without the expensive help of specialists;
- The building materials used are affordable;
- The large angle of inclination of the roof perfectly removes water during precipitation;
- Absence complex structures and kinks, greatly facilitate the construction and cladding of the roof.
To start calculating a gable roof, specify the scale of the drawings.
Select required option roofs: 1 - a simple gable roof, 2 - a roof with an adjoining element (the so-called dormer window). Please note that the second option is more difficult to implement and more expensive than the first, and the place of articulation (the so-called valley) is potentially dangerous place for the occurrence of leaks, which requires special attention during installation.
Fill in the dimensions in millimeters (mm):
Y- The height of the roof, the distance from the attic floor to the ridge. Affects the angle of inclination of the roof. If you plan to equip a non-residential attic, you should choose a small height (less material for rafters, waterproofing and roofing will be required), but sufficient for revision and maintenance (at least 1500 mm). If it is necessary to equip a dwelling under a roof arch, to determine its height, it is necessary to focus on the height of the tallest family member plus 400-500 mm (approximately 1900-2500 mm). In any case, the requirements of SP 20.13330.2011 (updated edition of SNiP 2.01.07-85*) must also be taken into account. It should be remembered that precipitation can linger on a roof with a small angle of inclination (small height), which negatively affects its tightness and durability. However, a high roof becomes more vulnerable to strong wind gusts. The optimal angle of inclination is in the range of 30-45 degrees.
X- The width of the building.
C- The size of the overhang. The overhang protects the walls and foundation of the house from atmospheric precipitation. For one and two-storey houses with drainage system minimum size C- 400 mm (according to SNiP II-26-76 *), without the organization of external water flow, not less than 600 mm. The optimal overhang is approximately 500 mm. Consider the climate features of your region in accordance with SP 131.13330.2012 "Construction Climatology" (Updated version of SNiP 23-01-99*).
B– The length of the roof, taking into account the overhangs beyond the gables.
If you have chosen roof option No. 2 (with dormer window), also enter the following values:
Y2– Height of the adjoining triangular element;
X2– Width of the base;
C2- Protrusion, i.e. distance from the base to the edge of the overhang.
Roof building materials:
S1- Rafter width.
S2- Rafter thickness.
C3- Rafter pitch, i.e. distance between adjacent rafters.
S1 And S2- important parameters that determine the reliability of the entire truss system. Rafter section (width S1 and thickness S2) depends on the loads acting on it. Own weight of the truss system, battens, roofing cake are constant loads; temporary - snow, wind; special - seismic effects, industrial explosions). Also, the choice of the width and thickness of the rafters is influenced by the quality and type of material used (board, timber, glued laminated timber), the length of the rafter leg, the distance between the rafters. Approximate section of the beam and rafter pitch ( C3) for different lengths is given in the table.
| Rafter length, mm | Rafter pitch, mm | Rafter section, mm |
| Up to 3000 | 1200 | 80x100 |
| Up to 3000 | 1800 | 90x100 |
| Up to 4000 | 1000 | 80x160 |
| Up to 4000 | 1400 | 80x180 |
| Up to 4000 | 1800 | 90x180 |
| Up to 6000 | 1000 | 80x200 |
| Up to 6000 | 1400 | 100x200 |
When choosing a section of rafters, it is imperative to take into account the recommendations of SP 64.13330.2011 " wooden structures» », SNiP II-26-76* «Roofs» and set the load bearing capacity in accordance with SP 20.13330.2011 «Loads and impacts».
C4– Roof outlet (overhang) from the side of the gables. Optimal value C4 approximately 500 mm.
O1, O2- the width and thickness of the board of the crate stuffed on the rafters. According to SNiP II-26-76 * "Roofs", the lathing is made of bars with a minimum section of 30 × 50 mm.
R– The spacing between the boards of the battens depends on the roofing material used (for example, the spacing of the tile wave). The value of the quantity R recommended by SNiP II-26-76* "Roofs". In particular, the base for the roof of asbestos-cement corrugated sheets - slate of civil buildings with an attic should be a crate of ordinary bars with a section of 60x60 mm. To ensure a tight longitudinal overlap, all odd-numbered lathing bars should have a height of 60 mm, and even-numbered 63 mm. The step of the battens of the crate should be no more than 750 mm. For lathing bars, coniferous wood is used in accordance with the requirements of SNiP II-25-80 “Wooden structures”.
L1 And L2- The length and, accordingly, the width of a sheet of roofing material depends on its type and production features. Pay attention to the compliance of the parameters declared by the manufacturer with regulatory documents (for example, GOST 30340-95 for slate, GOST R 56688-2015 for ceramic tiles, GOST 24045-2010 - corrugated board).
Approximate values for the length and width of roofing materials for a gable roof are shown in the table.
| Type of roofing material | Height L1, mm | Width L2, mm |
| Decking | 1000-1400 | 800-1200 |
| Slate (GOST 30340-95) | 1750 | 980, 1125, 1130 |
| Ceramic tiles | 310, 333, 347 | 190,190, 208 |
| bituminous tiles | 1000 | 317 |
| metal tile | 1120, 1180 | 1040, 1100 |
| Ruberoid | 1000 | 750, 1005, 1025 |
| Euroslate (Ondulin) | 2000 | 950 |
| Galvanized steel | 720-1800 | 2000, 2500 |
| roofing iron | 510-1000 | 710-2000 |
L3– Roof sheet overlap in percent. The value of the overlap depends on the type of roofing material, the angle of the roof and are regulated by SP 17.13330.2011 "Roofs" (Updated edition of SNiP II-26-76). The required overlap of the roofing material is often indicated by the manufacturer on the packaging.
The calculator allows you to calculate the dimensions of a gable roof: the length and width of the roof sheet for each slope, and the area of \u200b\u200bthe roof. The required length and number of rafters and battens for the construction of a gable roof truss system. The volume of lumber for the manufacture of rafters and battens. The number of rows of boards of the crate. Also, the calculator will calculate the gable and the height of the ridge of a gable roof. Calculate the amount of roofing and under-roofing insulating material required for a gable roof (necessary to provide vapor barrier, protect insulation and roofing material from condensate, calculated taking into account 10% overlap). With such data, you can find out the price of building a gable roof, more accurately determine the volume the right material. Notice what better materials for rafters, battens you can order, the lower your roof costs will be (less rejected wood). It is also advisable to consult a qualified roofer (especially if you have chosen the second roof option with an adjoining element), it is better not to make a mistake than to correct it later.
