Which Roof To Choose, Types And Structures Of The Roof

2023 Author: Philip Bishop | [email protected]. Last modified: 2023-08-25 07:54

Inclined rafters are, in essence, beams similar to floor elements, but installed obliquely on supports of different heights, and not horizontally. Supports for them at the gable roof are two outer walls, at the gable roof - the outer and inner walls. It is necessary to note one more important feature: the rafter legs of opposite roof slopes can be based on the ridge girder alternately, that is, it is not at all necessary to fix them in the same plane. The emphasis of the sloped rafters with the ends falls on the walls of the building, and in the middle part - on the intermediate supports. They arrange inclined rafters when the distance between the supports is not more than 6.5 m. The additional support makes it possible to increase the width covered by the inclined rafters up to 12 m, and two supports up to 15 m.

The support of the hanging rafters falls only on the ends of the walls of the building.

They only transmit vertical pressure as opposed to inclined ones. Hanging rafters are used when the roof span is 7-12 m and there are no additional supports. Hanging rafters in most cases are arranged in buildings with light walls, as well as in buildings where there are no internal load-bearing walls.

The basic elements of the hanging rafters are represented by rafter legs and lower belt ties.

Roof structure selection

If a roof structure with hanging rafters is chosen, then in this case all elements must be rigidly connected, since they represent a single structure, namely, a rafter truss resting on two extreme supports. Due to the absence of an average support, the rafter legs rest against each other in the ridge, as a result of which significant horizontal pressure is created, called thrust. In the event that the roof is not constructed correctly, the walls may even topple over. The task of damping horizontal pressure lies with the tightening - the lower chord of the truss truss.

The choice of construction and roof classification is determined by specific conditions. So, for example, inclined rafters have a simple device and do not require use when installing lifting mechanisms. Trusses with hanging rafters can be assembled on the ground, but in this case it becomes problematic to lift them onto the structure under construction. However, using a boardwalk, auxiliary braces, plank joining, you can mount the trusses directly on the house.

In wooden cobbled buildings, as well as chopped buildings, the support of the rafter legs falls on the upper crowns, in frame structures - on the upper harness.

In houses made of stone, a mauerlat in the form of beams with a thickness of 140-160 mm is used as a support for the rafter legs.

You can place the Mauerlat along the entire length of the building or put it only under the rafter leg.

If the rafter legs are small in cross-section, then over time they can sag. To avoid this, you should use a special lattice consisting of a rack, struts and a crossbar.

Planks with a width of 150 mm and a thickness of 25 mm, as well as wooden plates obtained from a log with a minimum diameter of 130 mm, are suitable for the execution of racks and struts.

To secure the rafter leg, use a puff. The rafter end when sliding over the tightening may damage its integrity. To prevent slipping, it is recommended to cut the rafter leg into the tightening with a thorn, a tooth, or both at the same time.

In addition, it is recommended to install the rafters at a distance of about 300-400 mm from the edge. When cutting a leg into the end of the tightening, it is necessary to move the tooth as far as possible.

If a reinforced rafter is required, a double tooth should be used.

In most cases, teeth are used that have different sizes: the height of one tooth is 0.2 of the puff thickness, and the height of the other is 0.3. It is necessary to preliminarily make an emphasis and a spike on the tightening and an eyelet on the rafter (for the first tooth). For the second tooth, one stop is enough.

In order to additionally secure the rafters in the puffs, clamps and bolts are used. The latter are used less often, since they lead to a weakening of the section of the rafter legs and puffs.

The final stages of installation are the construction of the ridge of the roof frame, sheathing of cornices (protruding 40-50 cm beyond the level of the wall of the free part of the rafters), erection of gable walls, as well as fastening the sheathing made of boards or bars.

Clamps made of steel strip or wire with a diameter of 5-6 mm are attached to the Mauerlat and the girder that make up the ridge knot with the help of large nails, and twists are performed.

To perform the connection of the brace with the rack in a complex ridge knot, it is necessary to hollow out the socket in the rack and cut a spike in the brace. To increase the strength of the connection, it should be additionally reinforced with bolts and clamps.

To connect the rafter legs with the crossbar, a cut is used. The strength of the connection is given by securing it with a bolt, bracket or dowel.

The main purpose of the roof is to protect the walls of the building from the negative effects of snow and rain, and therefore the length of the eaves should be at least 550 mm.

The ends of the rafter legs are attached to the wall in the manner described below. The brace-harness is put on the rafter-brace assembly, and with the second end it is tightened either on the beam of the attic floor, or on a crutch driven into the masonry or brickwork at a distance of about 30 cm from the upper edge of the wall. Otherwise, the tie-bundle is called a twist and is a piece of thick wire, preferably galvanized. In wooden log houses, instead of twisting, it is more expedient to use an iron brace, designed to connect the rafters with the second crown of the log house.

At one end, the reinforced concrete rafter legs of the inclined rafters are attached to the outer wall of the building, the other to a prefabricated reinforced concrete girder, which is supported by brick posts.

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