Hip roof truss system: design and installation features with your own hands

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Today the RMNT.RU portal will tell you about what a hip roof looks like and what it consists of. You will learn about the advantages and disadvantages of this type of rafter system and the installation features. The article provides a step-by-step guide for creating a do-it-yourself hip rafter system.

Hip roof rafter system

The hip roof or, in other words, the four-pitched rafter system is a popular and well-researched roof solution that allows the construction of large attic roofs. A design feature is an additional slope that replaces the pediment. This ramp has a triangular shape and is called a hip. A special case of such a slope is a half-hip, when the slope does not reach the border of the armopoyas.

The introduction of an additional slope (hip) into the gable roof structure provides the following advantages over the traditional layout:

  1. Load distribution to all four walls. The gable roof rests on only two. This is relevant in old buildings, the walls of which were erected in conditions of forced economy (from marl, adobe, bricks on clay mortar).
  2. The absence of a pediment reduces the wind load (windage) on the rafter system. It is a vital property in windy areas and for suburban homes. The roof section instead of the pediment does not give a significant load on the foundation. Moreover, its construction is faster and cheaper..
  3. Better access to sunlight. A ridge of shorter length is a smaller shadow of the “sail” of the entire roof. This is useful for adjacent buildings and the private sector.

Hip roof rafter system

Against the background of obvious advantages, the hip roof has some disadvantages:

  1. Inefficient use of attic space in homes with a wall ratio of no more than 3: 1 (one wall is no more than three times longer than the other). In multi-storey buildings, this is invisible due to the considerable length of the building..
  2. More complex construction. This is a double property, since the complexity of the rafter system implies more elements, which makes it technically more perfect – strong and rigid.
  3. Higher consumption of roofing material – the downside of saving on the gable.

In terms of the composition and quality of the material, the multi-pitched roof does not differ from other options. To date, the following dimensions of sections of the elements of the hip rafter system are relevant (you can find the terms and specific names of the elements in the previous article):

  1. Mauerlat. Board from 60 to 100 mm thick and 150 to 250 mm wide. Beam – from 100×100 to 200×200 mm.
  2. Central rack (headstock). Board with a thickness of 60 to 100 mm and a width of 150 to 200 mm. Beam – from 100×100 to 150×150 mm.
  3. Rafters, ridge, ribs, racks, rafter puffs – a board with a thickness of 50 to 75 mm, a width of 100 to 180 mm.
  4. It is recommended to use supporting and reinforcing metal products – brackets, plates, rods, anchors, turboprop, homemade or stamped factory fittings. Metal thickness – from 2.5 mm.

Do-it-yourself hip roof

Calculation of the main sketch

Note.A variant of the traditional (classic) hip roof with an angle of 45 ° to the horizon and vertical will be considered. Installation will require advanced carpenter skills.

Hip roof rafter system Classic hip with support a = b: 1 – ridge run; 2 – the height of the attic; 3 – central rack (headstock); 4 – hip slope; 5 – a number of wives; 6 – projection point of the connection of the ribs and the ridge; 7 – bed; 8 – floor beam (tightening)

The introduction of a hip into a gable roof implies the installation of additional skates for this slope. They are called ribs or rafters. The rest of the hip rafters are called rafters. In accordance with the laws of geometry, the length of the cuffs will depend on the height of the attic (subject to an angle of 45 °).

Based on the 45 ° indicator, you can easily calculate the basic proportional dimensions of the roof. The most important point when creating a sketch and transferring it to the terrain is the projection point of the junction of the edges and the ridge (hereinafter – the projection point).

Operating procedure

1. Install the Mauerlat on the armored belt using anchors to a depth of at least 1.5 times the Mauerlat thickness. Cutting corners – half a tree.

2. Install the beds and prepare the puffs.

3. Designate the projection points and install the support posts (with a margin of height) on them strictly vertically on strong temporary struts.

Hip roof rafter system

4. Determine the height of the ridge relative to a fixed horizontal plane – overlap or armored belt, mark and cut the racks in height.

5. Connect the racks with a ridge run (board) with a reliable tie and unfasten the central frame with slopes and straps (the central frame is the conditional name (row) of racks, ridge run and stanchion, interconnected by additional rods and slopes).

Hip roof rafter system

6. Install the rafter legs of two parallel ramps according to the design. Fasten with a temporary lathing and install the rafters (crossbars).

Hip roof rafter system

7. If the distance between the support rafters is more than 2.2 meters, an intermediate stop called a sprengel is placed under it. This is a vertical post mounted on a horizontal beam, fixed to the Mauerlat..

Hip roof rafter system

8. Trim in place, install and loosen the hip ribs. It is assumed that the eaves have been approved..

Hip roof rafter system

9. Mount the hip rafters of the main parallel slopes to the ribs of the hip.

10. Install the hip braces, securely fastening all the nodes using available methods – self-tapping screws, turboprops, threaded fasteners. Under each rafter leg, it is necessary to make cuts in the Mauerlat.

Hip roof rafter system

11. If the projection of the working part of the rafters is more than 1.5 m long, it is necessary to install intermediate posts.

Hip roof has two common special cases. Both varieties in some way affect the design of the joint of the ridge girder and the rafters..

The first case. Hipped roof

This is a type of roof consisting of four hips, that is, it does not have parallel pairs of slopes of different sizes. All rays are exactly the same. Basically, such roofs are used on gazebos or towers. The work progress will consist of points 2, 3, 7, 8, 9 of the previous instruction. Due to their small size and structural rigidity, they can be manufactured in a landfill or in a workshop and then mounted by crane.

Hip roof rafter system

Hip roof rafter system

The second case. Hip roof without internal supports

This option is suitable if you need to maximize the use of the attic space, for example, in commercial construction. In this case, it is better to make the hip slope angle flatter – 22.5 ° or less to the vertical, lowered to the projection point or 67.5 ° or more to the horizon. This is necessary in order to avoid excessive snow load..

This type of roofing makes up to 90% of the floor space useful. Moreover, its installation requires a lot of experience and ingenuity. The whole essence of the construction of this type of rafter system is reduced to construction on temporary supports, which are dismantled after the final release. The frame is held in place due to the rigidity and uniform tension of all elements – such a roof made of a profile pipe is an order of magnitude more reliable than a wooden one.

Of particular importance when creating an unsupported hip roof is the cleanliness of the fit (accuracy of cutting) of the elements and the reliability of the joints. Here it is necessary to use as much as possible metal elements, glue and threaded rods..

When installing any truss system, pay attention to the quality of the lumber. A few larvae of a woodworm or bark beetle are enough for any wooden rafter system to be destroyed within 10 years. Be sure to treat wood with special compounds..

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