Hip roof: design and installation rules

Recommendation points

• Description of construction
• Carrying system assembly procedure
• Methods of fastening and rallying used
• Related videos:
• Cold roof device
• Hipped roof and warm attic
• Hipped roof attics

Despite the strengths of the hip structure, it is rarely used in the construction of the roof due to its rather complex configuration. However, if you know the key features of the supporting system and the rules for making connections, there is no reason not to cover the house with one of the most beautiful types of roofing..

Description of construction

The hipped roof is prized mainly for its appearance. Due to the absence of gables and overhangs, the roof looks like a complete element of the architectural ensemble, allowing you to best realize the aesthetic potential of the roof covering. There are other advantages, the importance of which will be considered along the way..

The roof structure is a system of inclined rafter legs converging at a common top to form four slopes. The hip roof is a kind of hip roof, its top is stretched in a line, there is a horizontal ridge. Hip roofs are built on rectangular buildings, hipped roofs – on square or with an aspect ratio of up to 1: 1.3.

Unlike a gable roof, a tent-type rafter system experiences a load along all three axes, which requires high rigidity. In practice, this is realized by installing additional supports and using reinforcing elements of the frame in the main places where the load is concentrated. The main problem with this type of roof is the complexity of joints that converge at the wrong angles, which requires atypical trimming and the correct choice of connection method..

To install the tent frame, you will need to bring out the flat horizontal plane of the bearing walls, on which the belt is being erected. It can be a reinforced concrete tape 20 cm high or three rows of reinforced brickwork. This element has two functions: load distribution and the basis for attaching the supporting system to the walls. It is possible to avoid the device of a belt only when covering a stone house where the masonry has a density large enough to securely attach the Mauerlat.

Carrying system assembly procedure

The Mauerlat must be installed on the inside of the enclosing structures and securely pulled to them with anchor bolts or mortgage pins. Before assembling the trim under the roof, waterproofing must be laid on the walls. Since the Mauerlat is tightly attracted to the base, it will not work to level irregularities. Therefore, the upper plane of the walls must be leveled in advance with a screed or when pouring a concrete tape, and only a beam of calibrated thickness should be allowed on the strapping.

On top of the Mauerlat, an overlap is arranged, as a rule, of a frame type based on beams 50–100 mm thick and up to 250 mm high. The edges of the beams must be trimmed in such a way that they do not protrude beyond the Mauerlat and, at the same time, with their bottom edge they come out flush with the support plane, which will guarantee an almost even plane of the rough ceiling.

A roof support system is assembled on top of the slab. As a rule, this is a frame in which the rafters belonging to each slope separately are located parallel, their tops converge exactly on the mating lines between the slopes with the rafters of adjacent slopes.

In order not to be mistaken, it is better to pull the cross lacing diagonally in advance, then install vertical struts along these lines. Their height must be chosen based on the optimal elevation of the roof top and the steepness of the slope. The distance between the posts should be chosen so that the fulcrum of the long rafters is closer to their center, in which case the supporting structure will be balanced and most stable. On the other hand, in order to relieve the load on the floor, it is reasonable to place the support posts closer to the main walls. Final Support Frame Configuration – A Weighted Compromise.

First, straight rafters converging at one vertex must be installed along the centers of the Mauerlat and the crossbars of the supporting frame. If earlier during assembly mistakes were made and the rafters at the top do not converge, you can adjust the height of the supporting racks. Therefore, it is not recommended to finally fasten the joints until the final installation of all critical elements that form the roof geometry. By following this simple rule, you will not experience any difficulties in correcting flaws at this stage..

Corner prefabricated rafters are installed along the lines of convergence of the slopes. It is the longest and most heavily loaded roof load-bearing element, which must have increased reliability. The rafters must be assembled in the form of a three-layer sandwich. The inserts in the middle are designed for rallying and are installed in the places where the rafters rest on the Mauerlat, the supporting frame and at the very top.

When installing diagonal rafters, their alignment is required not only according to the position of the support points, it is necessary to achieve a strictly vertical position, without which it will not be possible to ensure the correct abutment of short intermediate rafters. On one side, they rest on the Mauerlat, on the other – the butt-end in the sidewall of the long diagonal rafter legs. After the intermediate rafters are installed with the required pitch, the main fasteners and additional supporting elements are installed, and then everything happens as in a conventional roof: waterproofing, counter battens with lathing and covering.

The calculation of the number and cross-section of the supporting elements of the hipped roof can be performed in the online calculator, which will give not only the optimal pitch and cross-section, but also the main parameters of the roof and full detailing with working sketches. When calculating manually, one should be guided by SP 64.13330.2011, taking into account the design requirements according to SP 17.13330.2011. 0 they are considered light rafters, installed with frequent steps.

Methods of fastening and rallying used

The junction of the intermediate rafters with the diagonal rafters is the most difficult. The hipped roof as a whole is difficult due to the fact that its alignment is difficult due to the lack of straight attachment points, therefore it is better if the correct configuration is ensured by the accuracy of manufacturing of parts that, after fastening, form a structure of guaranteed correct dimensions.

The quality of the lumber, which must be processed after drying and completion of the warping processes, also means a lot. At the time of assembly, the moisture content of the wood should be about 20% – as in covered storage for a month. If the beams have acquired a curvature of up to 2 mm / m, they can be used: due to the correct preparation of parts, it is possible to minimize the cumulative error.

Let us explain using the example of fastening intermediate rafters to diagonal rafters, where double trimming of the ends is required. As a rule, it is performed locally, but this is possible only with experience and high quality materials. To ensure correct trimming, it is best to perform trimming. First, the angle at which the central rafters are installed relative to the vertical is marked across the board. If the diagonal rafter legs are level, this angle will be the same in all places. If the boards are curved, by pressing them against the end of the short rafters during fastening, alignment will be ensured, and from both sides at once.

After trimming the rafters across, it is necessary to bevel at the end. Its angle is also known and is equal to the turn of the diagonal rafters relative to the Mauerlat. If the base is a regular square, this angle is 45 °, however, if the ratio of the lengths of the walls is unequal, this ratio can change, so the markings should be transferred with a small.

Initially, short rafters should be made of greater length with the expectation of subsequent trimming. And to increase the spot of support of the rafters on the Mauerlat, a notch should be made, retaining at least 60% of the original section. It is also not recommended to mark the trim in place here, because the nape of the serif ensures the correct position of the diagonal rafters. Therefore, it is reasonable to install the rafters sequentially along each fastening belt, starting from the bottom. Then, due to four identical parts in the correct position, possible twisting or inclination of the diagonal rafters will be eliminated.

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Another problematic knot is the convergence of the diagonal and cross rafters in the center. It is convenient to first join the transverse rafters in a straight end, strengthening the connection with studded L-shaped plates, or by imposing horizontal ties at a level of 40-50 cm below the top. After that, it is enough to cut the end of the prefabricated diagonal leg at the angle of rotation between the transverse rafters. For a square roof, it will still be the same 45 °, with unequal sides, the angle value will have to be measured individually on each side or transferred with a small.

When connecting some knots, it is better to abandon nails and definitely not use black self-tapping screws. For example, fastening the ends of short rafters to diagonal rafters is best done with anodized screws with pre-drilled holes. For attachment to the Mauerlat, pins with a large thread with a diameter of 10–12 mm should be used. The use of regular nails is allowed, either provided that they pass through and bend 25-30 mm, or if the knot to be reinforced with nails is a joining with undercut.

Tip: Rusty nails hold better than clean ones. Do not be lazy and soak them for a day in a jar with a strong solution of table salt.

To strengthen the roof structure and use materials with a smaller cross-section, a number of additional elements can be installed. For example, diagonal braces of the supporting frame, crossbeams between opposing legs, trusses in the corners of the Mauerlat and supports, prefabricated (double) transverse rafters, etc. However, we hasten to note that the tent structure itself perfectly distributes the load and for reliability you only need to accurately manufacture the parts and connect them correctly. Therefore, the installation of reinforcing elements is required only for hip roofs, or with a small slope of the slope with a significant length of it..

Cold roof device

When the supporting structure is fully assembled, it remains quite stable even without additional ties, however, due to the crate, an additional margin of safety can be provided. Therefore, hip roofs are often sheathed with sheet material, which allows a fairly frequent step of rafters.

In fact, continuous sheathing can only be made with FSF or bakelite plywood, or with special sheet materials for roofing on a chipboard basis. It is often more expedient to use a plank transverse lathing, first of all – when the coating has a large size.

The density of the lathing depends on the pitch of the rafters, the strength properties of the coating and the snow load. Specific requirements for resistance to deflection are set by the manufacturer of the coating, but there is a concept of fullness of the crate – the ratio of the area of ​​the boards to the total area of ​​the roof.

To ensure the correct operation of the cold roof cake, a counter-lattice should be used to create a gap between the waterproofing and the back of the covering. This will contribute to a full-fledged air exchange with street air, which means it will prevent high humidity and neutralize the effect of condensation that falls on the roof during sudden temperature changes.

Hipped roof and warm attic

A tent-shaped structure is considered the most suitable for the implementation of the concept of a warm attic. It allows the laying of exhaust ducts through the ceiling practically at any point without the formation of dead zones. Removal of air from the attic can be carried out through a single vent located at the highest point of the tent structure.

However, for this, a number of requirements for the construction of the roof must be met. The rafter legs should not protrude beyond the Mauerlat; instead of tamping the soffits, the facade is finished under a small projection of the coating. This imposes some restrictions on the choice of materials: only sheet format is suitable.

This requirement is justified by the need to seal the attic space. There are other methods for this, but they involve the use of more perfect and expensive thermal insulation, while in the simplest case, it is enough to insert mineral wool between the rafter legs, having previously calculated their step.

In its completed form, the pie of the roof over the warm attic is an uncovered insulation that is supported by a mesh. To eliminate the effect of condensation, a superdiffusion membrane should be installed on the inside instead of waterproofing. Otherwise, there is a risk of condensation formation on the back of the hydro-barrier, which is unacceptable for mineral thermal insulation. Thus, instead of buying an expensive insulation that is not afraid of moisture and meets fire safety requirements, it is enough to spend only on high-quality steam and water protection..

Hipped roof attics

In the case of a mansard roof, the requirements for thermal insulation of the floor and the roof are different. It is unacceptable that the atmosphere in a living room is even partially formed by exhaust air from other rooms. This requires some effort when installing ventilation – both internal and under-roof.

You can also use mineral wool for these purposes. Except for the ventilation system, then to turn a warm attic into a habitable one, it is enough only to complete the inner lining, under which there is a duct and vapor barrier. At the same time, the roof cake remains localized between the two layers of protection, it is only important that the throughput of the upper one is higher. In the simplest version, for this it is enough to cover the attic from the inside with plastic wrap, which will completely limit air exchange. This problem can be solved in several ways:

1. Installing vents through the roofing pie
2. Application of high-quality vapor barrier with a reliably known difference in vapor transmission capacity.
3. Insulation with a sprayed material, which does not eliminate the need to install ventilation, but retains usable area and does not require vapor protection from the inside.

The attic space under the hipped roof has limited planning, because literally in the center are the racks of the supporting frame. However, due to the displacement of doorways and non-capital partitions, it is possible to beat the space with the formation of several separate rooms, or one large room, separated by formal partitions. But you need to take into account the thickness of the racks in advance, so that when erecting internal walls, their thickness allows you to correctly hide the supporting elements, without using too heavy materials.