Formation of the roof is an important and responsible stage of construction houses. It depends on him how the building as a whole will “feel” later. Comfort and, no less important, durability - directly depend on the quality of the work performed.
There are a sufficient number of design solutions, but the gable roof truss system, due to its popularity with homeowners, deserves separate and closer attention. “The simpler, the better” - this is exactly about her.
However, despite the elementary design, there are points that can significantly reduce its service life. To avoid negative consequences, you need to find these “pitfalls”, and for this you will have to plunge a little into theory, get acquainted with a few terms and consider some practical recommendations.
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Double roof construction
Gable roof
The fundamental device of the gables is elementary, and consists in the presence of roofs two inclined rectangular planes, along which precipitation is discharged, whether it be snow or water.
These planes converge from above in one horizontal line, called the “ridge”. When constructing such a geometric shape, two vertical triangles are inevitably formed from the ends of the slopes - the pediment.
Types of gables
Differences in fastening rafters
Classic - the most common design. With this arrangement, the roof is formed with symmetrical slopes, i.e. with the same steepness.
In its construction, a simple “two-slope” can be formed in two ways:
- layered
- hanging
These systems will be discussed in more detail below.
Roof of a frame house
The advantages of this variation are obvious:
- Simplicity in design. Almost everyone who knows the basics of mathematics can cope with the calculations. There are many ready-made projects that are in the public domain
- Design reliability. The minimum number of connecting nodes makes it strong and durable
- Ease of installation. There is nothing “tricky” here - there are few elements, nodal connections are elementary, the tool is simple, fasteners are available
- Classic design is always in fashion. In addition, if desired, the homeowner can easily change the look of the house by changing the angle of inclination of the roof slopes.
Asymmetrical shapes - it's unusual. However, if the symmetry is broken, the balance in the distribution of the load is disturbed, which inevitably entails a significant complication in the supporting “skeleton” of the entire structure. It is extremely difficult to calculate such a project on your own. In this case, you will have to use the services of professionals
Asymmetry is beautiful
Mansard type of roof - another variety. It differs from the classical variation in that the pitched surface is created broken.
Its design is somewhat more complicated than that of its classical counterparts, but it is also accessible to a simple layman who decided to project and assemble it on his own.
The main difference from the classics is that the attic type combines both technologies used for the construction of roof trusses.
Terminology and elements
Versions
For a full-fledged study of roofing topics, special terminology is indispensable. For the purpose of clarity, below is a diagram with examples of the use of the described elements.
The main elements of truss systems
- Maurlat - element of almost any roofing structure. It is made of a wooden board or beam, rigidly fastened around the perimeter of the end face of the outer walls of the building. Its main purpose is to evenly distribute the load on the load-bearing walls of the building. It is to this element that all the rafter legs of the roof are attached.
- Rafter - load-bearing frame for roofing. They are installed in pairs, connecting to each other in the upper part, called the ridge. The lower part of them, as already mentioned, is attached to the maurlat. The rafters exposed with a certain step serve as the basis for the lathing, on which the roofing material will be attached in the future.
There are many questions about connectors - a good video can be found at the following link:
VIDEO: Rafter system nodes
Rafter system nodes
Why are gable roof truss systems so popular? Overview of advantages and key differences (Photo & Video)
- Bolt and (or) tightening. Structural reinforcement elements. They are installed horizontally, cut into rafter pairs, attached to nails, bolted connections, etc. If necessary, to give additional rigidity, they are duplicated two or three times (upper - middle - lower)
- Rack or grandma - serves as both the main and additional vertical support. They eliminate frame deflections
- Runs - timber, one or two stitched boards, and there may also be a separate structure. In simple versions, the ridge run is sewn to the nodal connections of the upper part of the rafter legs; in more complex ones, it is supported by pasterns (vertical posts), which, in turn, are attached to the bed
- Lezhen - this is a running beam, i.e. timber, lying along the entire length of the roof. It is formed for additional fixation and strengthening of the entire roofing formation. It can be laid both on the load-bearing partition of the building, and only on external walls (in two places)
- Struts - reinforcing detail. They are used in cases where the rafter legs have an increased length, when there is a need to further strengthen and eliminate their deflection. The more complex the roof, the more of these parts may be required.
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Types of gables
If everything is clear with the fundamental device, then specific solutions still need to be dealt with. Buildings are diverse, and each requires specific solutions. There are a lot of different schemes, but all of them can be divided into two types according to one criterion: fastening the skate. Let's consider them in more detail.
Rafter system
Layered system
It should be noted right away that this design is loved by roofers for its reliability and easy installation.
The basis for fastening the rafter pairs in this system are the maurlats and the ridge run, which is installed on vertical beams, which, in turn, are attached to the bed.
Thus, the following picture is obtained - each pair of roof rafters is rigidly fastened in three places: two knots on maurlats and one on a ridge run. It turns out a very strong construction, with an excellent margin of safety.
Depending on the length of the rafters and the angle of inclination of the slopes, the structure can be supplemented with reinforcing elements: puffs, crossbars, struts, rafters, etc.Also, in the absence of a capital internal partition in the building, it is permissible to use a ceiling beam as a bed.
Hanging truss system
Layered system
The fundamental difference from the layered system is that only maurlats are used as a support for the rafters, i.e. wooden bars, rigidly fixed at the ends of the outer walls of the house. Above, on the ridge, the rafters have no support, they are only knocked together, and, as it were, “hang” in space - this is the defining criterion of this technology.
This system is used in the construction of buildings that are small in width, as a rule, it is no more than 7-8 meters. With an increase in these values with this technology, it will be necessary to install additional elements - crossbars and puffs, which to some extent will convert the pressure forces on the external walls and distribute the load more evenly.
The greater the width of the building, the more reinforcing elements the roof will be equipped with.. The diagram above clearly shows the ratio of the width of the covered span to the number of additional parts.
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Design and installation of a symmetrical gable roof
For solid houses with complex geometry, a professional project is required, which will take into account various factors: wind rose, precipitation statistics, building location, materials used, etc. It is extremely difficult to create such a project on the knee.
Snow won't hold at that angle
However, if you need to design and independently build a small roof for your country house, without any frills and complex design solutions, you just need to adhere to some well-known truths and rules:
- The higher the roof, the greater the wind load. The lower, the higher the snow
- The higher the roof - more attic space, and, accordingly, useful
- The standard step between the rafters is 60 cm between the axes of the latter
- For rafters, a board 150x50mm is used, a beam for supports 100x100mm., maurlats from a beam of at least 150x150mm
- The cheaper the board, the larger the geometric error (about 1 cm)
- Rafters and supports are allowed to build up
- The longer the board used, the more junctions and crossbars are needed
- Two main forces act on the connecting nodes: shear and tear
- The rafter is more securely held if a seat is formed in it
- Special mounting screws are a great thing, but expensive. Nails and staples are inexpensive and have stood the test of time, the sting of the latter must be bent
- The ridge of the rafters is not tightened with bolt fasteners - it may burst over time
- A tree does not like to lie on a brick or stone - it will eventually turn into dust. Waterproofing will not remove the cold bridge, thermal insulation is needed - then there will be no condensation
- A freshly cut frame shrinks, so you should not firmly fix the rafters (make seats in them) to the maurlat, otherwise the roof ridge will lead
Installation procedure for the “classic” hinged version
Anker can handle it
Installation work is not difficult, two people can handle it. What can not be said about the preparation and transportation of the material to the site.
First of all, maurlats are laid along the perimeter of the load-bearing walls (according to the level). A heat-insulating material is laid between the brick wall and the wooden beam to remove the cold bridge, thereby removing the possibility of condensation at the junction of stone and wood. This will protect the wood from rotting, and the brick from destruction.
Fasteners can be:
- bolted studs pre-fixed into the wall
- anchor bolts fixed directly in place
- metal reinforced U-belts or ordinary metal wire, pulled together with a mount
Installation of the truss system
Then comes the stage of preparing the rafters: length adjustment and formation of seats for maurlat.Since this technology does not provide for a ridge run, and it is problematic to carry out manipulations with the markup on weight - you will still make a mistake, and the plane will turn out to be wavy, then a temporary run is formed from the 50th board.
With the help of a cord, the middle of the ceiling space is beaten off and temporary grandmothers are set according to the level, to which the 50th board is sewn. All dimensions should be taken into account so that the ridge board is set exactly in the middle and to the required height. All pairs of rafter legs will be marked and exposed along it.
Run first, then the rest
Attaching each board to the run and the maurlat, markings are made for cutting the seats. To speed up work at this stage, you can use a previously prepared stencil. For its manufacture, you can use a square "Swenson".
The ridge is formed by focusing on each other paired rafters. To do this, putting a pair in place, using a level along the axis of the run, draw a perpendicular on one board. After drinking, they put it back and mark it on the second board. Saw off, set back and knock together boards.
Board layout
After mounting each pair, the upper crossbar is installed. Why put the board at the required height, set it horizontally according to the level, mark it and make a cut for the seat in this place, sew it on, cut off the excess.
Washed down is done only for the carrier crossbar. For other puffs, this operation is not necessary, it is enough to use nails and staples.
The step between the axes of the rafter legs is 60 cm.
Further steps for the formation of the roofing "skeleton" are similar.
Also, to facilitate understanding of the installation principle, it is recommended to familiarize yourself with the following informative video:
VIDEO: Construction of a frame house. Rafter system. Build and Live
Construction of a frame house. Rafter system. Build and Live
Why are gable roof truss systems so popular? Overview of advantages and key differences (Photo & Video)
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time tested
How many houses exist, the same number of gable structures exist. They are time-tested, they are easy to manufacture, economical and pretty enough. If you need an inexpensive, but reliable roof that will keep you cozy in the house for a long time, then gables are what you need.
