Roof system roof

By Admin | Roof And Roofing Materials
10 April 2016

to rebuilt the house served for many years as a strong and reliable, it needs not only a good foundation.Another significant element is the roof truss system, which takes care of all the vicissitudes of the weather.And she shall bear with honor the load in the form of wind gusts, heavy snowfall and heavy rains.Let's talk about how to construct and how to build this system.

Rafter roof system, its structure, types and fasteners


  1. Requirements to truss system
  2. main part of the structure truss system
  3. shape of the roof and roof systems
  4. types of roof systems - how do they differ among themselves
  5. Fasteners
  6. Video: Rafter roof system, you need to know to properly design

Requirements to truss system


First of all, every detail of the system and the joints have to be rigid, not deformingunder shear or thrust force when.The basis of the whole structure - the triangle.It has shaped frame (farm), which are fixed in parallel to each other.Their rigid fixation of the roof provides the necessary stabilit

y.But if the farm to get moving, and close to the disaster.Such a defective roof itself may be destroyed, and the walls of landslides.


roof should not be heavy, so a system of trusses, usually made of wood.If the solid weight of the roof, the base substrate is made of metal.Or take a conifer, is not lower than first grade, with humidity below 18 percent.Use antiseptic treatment and the use of fire retardant for fire protection - two mandatory conditions.Then the attachment points of the roof truss system are strong and sturdy.

High quality material

Wood for rafters should be as follows:

  • Wood takes 1 - 3 grades.Cracks and knots should be minimized.At 3 meter can be a bitch with a maximum height of 3 cm. Cracks not allowed throughout the depth, up to half the length of the board.
  • Bearing elements are made of wood pieces with a thickness of 5 cm, with an area of ​​40 cm2.
  • Conifer boards can be up to 6.5 m, and deciduous - up to 4.5 m.
  • Runs, pillows and mauerlat made of solid hardwood.They are treated with antiseptic.

main part of the structure truss system

Thinking device roof truss system, it is necessary to know any of the details, this is the system consists.

# 1. mauerlat - it is like the foundation of the entire system.It helps to evenly distribute the load on the walls.

# 2. Rafter leg determines the angle of slope, and the general appearance of the roof, firmly fixing the individual elements.

# 3. Run - strengthens leg rafters.Ridge Run at the top, the side girders - side.

# 4. Tightening - does not disperse the rafters, joining them at the bottom.

# 5. Racks and struts - provide additional stability feet rafters.They rest on the sill (the bottom of which lies parallel to the roof ridge).

# 6. Crate - stuffed perpendicular to the rafters and is edging bars or boards.It is intended to transfer the entire load of roofing material on the rafters.

# 7. roof ridge - it is a junction of two roof slopes.Along the ridge stuffed solid crate to reinforce this part of the roof.

# 8. filly - used to create the eaves if the length of rafters is not sufficient.

# 9. eaves - an element designed to protect against contact with the walls of excessive rainfall.

Components of the roof system

Now consider a complex site like truss.It has a flat shape, and included in it, except for the rafters, banners, pillars and struts.They are positioned so that the load on the wall inside the house does not occur.Just outside its walls are the supports, the load is vertical.The distance between farms is determined by calculations.If the span is large, the farm consists of several parts.In the attic lower belt farm serves as a ceiling.

Roof trusses
above are examples of wooden roof trusses, in addition, in some cases, used farm made of concrete and metal.

shape of the roof and roof systems

Pent roof.

The simplest roof system has a roof with a slope which is inclined at an angle of 14 to 26 °.If the house is small, and the span was not more than 5 m, it needs a system of rafters naslonnogo type.It relies on the exterior walls, as well as on the wall inside the building (if any).When the span of more than 5 m, it is necessary to use trusses.

The device pent roof
device pent roof trusses.

gable roof

roof with two slopes is also easy, it is located under the attic or loft.Its bias from 14 to 60 °.If the outer walls are separated from each other by less than 6 meters, make a hanging truss system.Naslonnye rafters should be used when the flight is large and has internal support.

Gable truss system
device hanging and naslonnyh rafters gable roof.

  • Read more about it in the material: a gable roof Rafter system and its device

hipped roof

roof with four slopes called hip or poluvalmovaya.Its slope is from 20 to 60 °, and the span may be - 12 m. In this case should have an internal support.Gable walls in this case are not available, which saves material.However, the installation of such a roof is more complicated than a gable.For such a design roof truss system made either naslonnogo type, or with the use of roof trusses.

Hipped roof
Design features a hipped roof.

scrap roof

a broken roof or loft, downstairs can be sloped 60 °.But at the top it is generally flatter.In this area of ​​the loft increases.This roof is good for homes where the width reaches 10 m. As in previous cases, the system can be used naslonnuyu rafters.However, the farm is preferable to use.

Breaking roof
device polygonal roof.

  • above are the most common, but not all forms of roofs, details see material: Types of roofs of private houses on the structure and geometric forms

types of roof systems - how do they differ among themselves

choose one or the other type of roof system is notspontaneously, but depending on the design of a house under construction and size.Next, for each form of roof systems.

system with hanging rafters

They are good for roofs with two slopes, where the flight is not more than 6 meters, and the walls inside are not available.Below is mauerlat support rafters, and at the top - they rely on each other.Yet there is a tightening, reducing thrust rafters to the walls of the house.Beam tightening placed in the bottom of the rafters - they simultaneously serve as ceiling beams.Incidentally overlap the upper floor made of reinforced concrete, can also play the role of tightening.If the tightness of doing higher, she had already called bolt.If span between the outer walls of 6 m requires the use of struts and braces to maintain the rafters.The length of the bottom of the rafters t. E., After the backup, should not exceed 4.5 m.

Examples of hanging rafters

list some important facts about their design:

  • rely roof overhang on the bottom of the rafters, retiredoutside the walls, it is not necessary.It is much better to support the roof of roof systems fit filly (the width of the overhang is made up to a meter).And then the whole plane of the leg will be based on mauerlat.The cross-section is usually less than fillies section rafters.
  • on-ramp is necessary to beat the wind board, from the ridge to mauerlat.The slope makes from the attic.It is necessary to become a rigid roof, not falter and are not destroyed by the wind.If the humidity
  • wooden roof material more than 18%, prepared for the fact that the system of rafters when dry wood can be shaky.Therefore, this tree does not connect with nails and screws - they can pull if something happens.Better yet, use screws or nails ershennye.

Naslonnye truss system

They are suitable for roofs, where the span is 10 to 16 m. The slope can be anything, but inside the building must be load-bearing walls or columns.At the top of the rafters rest on the bottom of the ridge pole - mauerlat.Ridge Run supported or inner wall (sleepers) or racks.Since there are only vertical load, the tightening needs no.

When span large (up to 16 m), can be replaced by two side ridge run, which will rely on the rack.To not bend rafters, struts and girders needed.If the attic is made, support can make naslonnyh built wall with a height of 1 to 1.5 m. Well, or apply a broken mansard roof (with broken slopes).

Examples naslonnyh roof systems

What should pay particular attention to:

  • Each of the elements of the system should not have a thickness of less than 5 cm.
  • progablevannaya smooth surface of all nodes truss system - a necessary condition.So they do not progniyut not as much will be subject to fungus.
  • Adding additional nodes "from the lantern" in the calculated system of trusses is prohibited.Otherwise, the load may not be where you want them.
  • mauerlat (his sole) shall lie horizontally with respect to the walls.Requires a horizontal surface, and with the docking mauerlat rafter foot.Otherwise, it may tip over and support.
  • Racks and struts have the most symmetrical.
  • to the rafters are not soaking and rotted, do a good ventilation.To this end, the roof of the attic provide the slit in the roof of the attic - the air holes.
  • Where truss assemblies are joined with masonry, waterproofing is necessary.And condensate ruin tree.
  • Not having a support strut or leg rafters, it is no longer than 4.5 m.


To get a reliable roof, roof system components must be properly connected.It should thus take into account the direction and strength of stress (both static and dynamic).And it is important to provide for the possibility of cracking of wood shrinkage, by ensuring that the nodes of the rafters is not stopped working properly.

Previously all parts truss system fastened together notching.It is reliable, but not too sparingly.After all, it is necessary to have a large wooden structure section that would allow to do cuttings safely weakening wooden elements.

Therefore, at the present time do not fasten the rafters nodes notching, and dowels and screws.

The means of fixing the rafters
methods of fastening rafters.

popular use of perforated steel lining having a cover against corrosion.Secure pad with nails or plates with teeth, recessed into a tree.Such fasteners for roof system is convenient because:

  • pads reduce wood consumption by a fifth since the required elements of a smaller cross section than when notching;
  • they can be mounted with the master is not very great experience;
  • they are fixed very quickly.

Mounting plates for trusses
perforated plate is used to attach rafters.

Lastly can see useful video which focuses on all the most important moments of the construction of the roof truss system.

material was prepared by the project authors SRBU.RU

Video: Rafter roof system, you need to know to properly design

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