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A wooden roof is a complex engineering system consisting of many interconnected elements that together form a supporting frame for laying the roofing covering and ensure the durability, strength, and stability of the entire roof structure. The foundation of this system is the truss structure, which receives and redistributes permanent and temporary loads: the weight of the roofing system, snow cover, wind pressure, as well as live loads from equipment and people performing maintenance. Typical details of wooden roofs are the key connection points of individual truss system elements with each other and with other structural parts of the building (walls, floors, columns). The correctness of design and the quality of execution of these details directly determine the load-bearing capacity of the roof, its geometric invariability under load, its ability to resist deformations, as well as the overall safety and longevity of the entire building.
Historically, wood has been and remains one of the main materials for constructing roofs in private and even some public construction, due to its availability, good strength characteristics relative to its light weight, and the possibility of creating complex architectural forms. However, wood is an anisotropic, hygroscopic material susceptible to biological degradation, so the design of details must consider these features. Modern approaches to constructing wooden roof details synthesize centuries of carpentry experience and achievements in structural mechanics, materials science, and normative design. Each detail must be not only strong but also technologically feasible for manufacturing, ensure the possibility of assembly on the construction site with allowable deviations, and also account for the shrinkage of wooden elements (especially when using wood of natural moisture) and fire safety requirements.
Structurally, the truss system consists of a number of typical elements: wall plate (top plate), rafters, purlins (ridge, side), tie beams, posts, struts, collars, sills, and sheathing. The connection of these elements forms details, each of which solves its own task. For example, the detail of the rafter bearing on the wall plate transfers thrust and vertical loads to the building walls. The ridge detail provides the connection of rafters at the top and forms the slope geometry. Details involving tie beams and posts allow covering large spans without intermediate supports, creating free space on the attic floor. An incorrectly calculated or executed detail becomes a “weak link” that can lead to sagging rafters, loosening of the structure, and in the worst case – collapse. Therefore, in this article, we will analyze in detail each typical detail of a wooden roof, examine the principles of its operation, structural solution options, fasteners used, and common errors made during construction.
Wall Plate (Top Plate) and the Detail of Its Attachment to the Wall
The wall plate (top plate) is a fundamental element of the truss system, which is a beam (less often a board) laid along the perimeter of the building’s external walls. Its main purpose is to evenly distribute concentrated loads from the rafters along the entire wall length and transfer them to the load-bearing structures. Without a wall plate, point loads from rafters could cause destruction of the masonry or local deformation of the wall material. For wooden and frame houses, the role of the wall plate is often performed by the top log of the log house or the sill plate, simplifying the structure. For buildings with masonry (brick, concrete, aerated concrete) walls, the installation of a wall plate is mandatory.
The cross-section of the wall plate is usually chosen within 100×150 mm, 150×150 mm, or 200×200 mm depending on design loads and wall thickness. Most often, beams made of coniferous wood (pine, spruce, larch) with a moisture content of no more than 18-20%, treated with antiseptic and fire retardant, are used. Before laying the wall plate, a layer of horizontal waterproofing is necessarily arranged on top of the wall – usually two layers of roofing felt, glass isol, or a modern bitumen-polymer membrane. This prevents capillary suction of moisture from the wall material into the wood and protects it from rotting. The detail of attaching the wall plate to the wall is one of the most critical, as it must withstand not only vertical but also significant horizontal (thrust) forces tending to shift the roof off the walls.
There are several main methods for attaching a wall plate to masonry walls. The classic and most reliable method is attachment to studs pre-embedded in a reinforced concrete belt or masonry. A reinforced concrete belt (seismic belt) is a monolithic reinforced concrete belt along the top of the wall, which increases the spatial rigidity of the building and creates a perfectly level and strong platform for installation. During the tying of the reinforcement cage, threaded studs with a diameter of 10-16 mm are vertically installed in it at 1-1.5 meter intervals. The length of the studs is calculated so that after pouring the concrete and laying the wall plate, a nut with a wide washer can be screwed onto the thread. Corresponding holes are drilled in the wall plate, it is placed over the studs, and then the nuts are finally tightened. This method provides a rigid connection, completely eliminating displacement.
The second common method is attachment using anchor bolts, chemical anchors, or wedge anchors. It is used if a reinforced concrete belt is not provided. In this case, holes are drilled in the masonry to a depth 2-3 times exceeding the thickness of the wall plate, into which anchors are driven or screwed. This method requires high marking accuracy and is less reliable on hollow materials (porous ceramic, aerated blocks), where special anchors for cellular concrete or chemical anchoring must be used. The third method, outdated but sometimes used in light structures, is attachment with annealed steel wire with a diameter of 4-6 mm, which is embedded in the masonry 2-3 rows before the top of the wall, then passed through holes in the wall plate and twisted. The fourth method is attachment with brackets, when wooden plugs (dowels) are driven into the masonry and the wall plate, and then brackets are inserted into both the plugs and the wall plate.
After reliably attaching the wall plate to the walls, they proceed to marking and preparing places for installing the rafters. It is important that the top plane of the wall plate is strictly horizontal, checked with a water level or laser level. Any unevenness can lead to misalignment of the entire truss system. It is also necessary to ensure reliable corner connection of wall plates on adjacent walls. This is done using half-lap or dovetail joints with additional fastening with steel plates, brackets, or studs. Thus, a properly arranged wall plate attachment detail creates a strong and stable foundation for the entire wooden roof, on which the success of subsequent construction stages depends.
Detail of Rafter Bearing on the Wall Plate
The detail of the connection between the rafter and the wall plate is key in terms of load transfer and ensuring the stability of the truss system. The structural solution of this detail depends primarily on whether the system is a purlin system (thrust or non-thrust) or a hanging system. In purlin systems, rafters work as inclined beams, bearing with their lower end on the wall plate, and with their upper end on the ridge purlin or the opposing rafter. In hanging systems, the rafters bear with their lower ends on the wall plate, and with their upper ends against each other, creating thrust, which is absorbed by a tie beam.
For non-thrust purlin rafters, the bearing detail on the wall plate should allow for slight rotation and horizontal displacement (sliding) of the rafter’s lower end under changing loads and humidity. This is necessary to avoid transferring horizontal thrust to the walls. Such a detail is usually executed in one of two ways. The first way is a connection with a “birdsmouth” and “tenon.” A so-called “birdsmouth” – a stop – is cut into the rafter, which prevents the rafter from shifting along the wall plate. For additional fixation, a tenon may be cut, and a corresponding mortise in the wall plate. This is a traditional carpentry joint requiring high skill. The second, more modern way is the use of metal fasteners, so-called “sliding supports” or sliders. These are perforated steel plates, one part of which is attached to the rafter, and the other to the wall plate, with the connection between them made through a longitudinal slot, allowing the rafter to move along its axis. Such a detail is ideal for houses made of timber or logs that are subject to shrinkage.
In thrust systems (which include hanging rafters), the detail must be rigidly fixed to transfer the thrust to the wall plate and further to the walls. Here, rigid fastening is used. The simplest option is fastening with steel angles or perforated straps on both sides of the rafter, screwed with self-tapping screws or nailed with ring-shank nails. A more reliable method is a combined approach: notching the rafter into the wall plate to a depth of no more than 1/3 of its height (so as not to weaken the load-bearing capacity) with subsequent fixation with brackets, angles, or through steel plates with bolts. It is important that the bearing area of the rafter on the wall plate is sufficient for transferring vertical pressure. To increase this area, they often use short blocks (false rafters) or make a notch (heel) in the rafter.
The practical sequence for constructing the detail is as follows. After marking the positions of the rafters on the wall plate, the rafters are prepared. One “standard” rafter pair is manufactured on the ground using a template, which is then used as a sample for the rest. At the lower end of each rafter, the necessary notch (straight, “seat cut,” or “bird’s mouth”) is cut for tight fit to the wall plate. The upper end is prepared for connection at the ridge. Then the rafter is placed in position. First, it is temporarily fixed, checking verticality and position in space. After checking the entire system, final fastening is performed using the chosen method. If notching is used, the rafter is additionally tied to the wall plate with a twist of wire, which is attached to a steel pin driven into the wall below the wall plate. This is an old but effective method against the roof being torn off by hurricane winds. In modern construction, anchor straps that wrap around the rafter and are attached to the wall are used for this purpose.
Quality control of this detail includes checking the tight fit of the rafter to the wall plate (gap no more than 5 mm), absence of cracks in the notches, reliability and sufficiency of the number of fasteners. Fastening elements (nails, screws) should not be placed too close to the edge of the wooden element, as this can lead to splitting. It is also important that there are no gaps between the wood and metal parts (angles, plates) – they should be tightly pressed. A correctly executed bearing detail ensures stable operation of the rafter in bending and reliably holds it in place under any operational loads.
Ridge Detail of a Wooden Roof
The ridge detail is the connection of the upper parts of the rafters, forming the apex (ridge) of a gable or multi-slope roof. This detail is key to ensuring the geometric invariability of the truss system in the longitudinal direction and for receiving bending moments in the upper zone of the rafters. The design of the ridge detail also depends on the type of truss system and can vary from a simple abutment of rafters to each other to a complex system with a ridge purlin and additional stiffening elements.
In hanging truss systems, where each rafter pair forms a rigid triangle with a tie beam, the ridge detail is the junction of the upper ends of two rafters. The connection can be made in several ways. The simplest is butt joint. The rafter ends are cut at an angle corresponding to the slope angle and joined together. For fixation, steel plates (wooden or metal) are used, installed on both sides and fastened with bolts or powerful screws. A more traditional method is a half-lap joint. Mortises are cut at the rafter ends to half the thickness of the beam, then they are overlapped, forming a cross. This joint is additionally tightened with a bolt or stud. Such a detail has good load-bearing capacity and stability. In some cases, the upper ends of the rafters are not directly connected but bear against a horizontal collar beam (ridge tie) located slightly below the ridge. This solution unloads the ridge detail and is often used in attic roofs.
In purlin truss systems, where the rafters have an intermediate support in the form of a ridge purlin, the ridge detail is arranged differently. The ridge purlin is a horizontal beam running along the entire ridge and supported on posts or internal walls. The rafters bear with their upper ends on this purlin from both sides. The connection of the rafter to the purlin can also be done in different ways. Often, a notching method is used: a “seat” – a recess according to the shape of the purlin – is cut into the rafter to provide a larger bearing area and prevent transverse shift. For fixation, steel angles, brackets, or perforated plates are used. In modern frame construction, connection using steel perforated brackets (beam hangers) is widely used, which are placed over the purlin and nailed or screwed to the rafter. This is fast, technological, and reliable.
The technology for assembling the ridge detail requires accuracy and attention. Usually, the outer rafter pairs (gable) are installed first, which are temporarily braced with struts. A cord is stretched between their top points, serving as a guide for installing the ridge purlin (if present) and all intermediate rafters. During installation, it is important to control that all top points of the rafters are in the same plane; otherwise, the ridge will be wavy, creating problems when installing the sheathing and laying the roofing covering. After installing all elements, the ridge detail is reinforced with additional connections. In systems with a ridge purlin, these can be wind braces (diagonals) between the rafters and the purlin, preventing longitudinal deformation of the roof. In systems without a purlin, transverse rigidity is provided by collars installed in a staggered pattern or diagonal braces.
In addition to the main load-bearing function, the ridge detail is a crucial element for organizing ventilation of the under-roof space. Even with a tight connection of rafters or abutment to the purlin, it is necessary to provide a gap for air exit, which enters through the eaves vents. For this purpose, the ridge purlin is often made composite (from two beams with a gap) or a gap is left between the upper ends of the rafters, which is then covered with a ridge board. Modern ventilated ridge systems for soft roofs are also mounted directly on the ridge detail. Thus, the ridge detail is not just a connection point but a complex multifunctional element, on the quality of which the stability, durability, and proper functioning of the entire roofing system depend.
Details with Tie Beams, Posts, and Struts in the Truss System
To cover large spans without intermediate supports or to create a free layout of the attic floor, the truss system is supplemented with elements such as tie beams, posts, and struts. Their main task is to reduce the design length of the rafter (and, consequently, the bending moment) and redistribute loads to internal load-bearing structures or to external walls. The details connecting these elements to each other and to the rafters require careful calculation and precise execution.
A tie beam (collar tie) is a horizontal element connecting the lower parts of the rafters in a hanging truss. It works in tension, receiving the thrust that arises from the weight of the roof and the tendency of the rafters to spread apart. Thus, the tie beam turns a pair of rafters into a geometrically invariable triangle. The detail for attaching the tie beam to the rafters is usually located at the base of the rafters or somewhat higher; in the latter case, it is called a collar beam and works not only in tension but also partially in bending (for example, when used as a base for finishing the attic ceiling). The connection can be made with a frontal notch, where the end of the tie beam is notched into the rafter, or with an overlay fastened through steel plates and bolts. To prevent sagging of long tie beams, additional elements – king posts (suspensions) – are suspended from them. The detail for attaching the king post to the tie beam and to the ridge detail must also be designed for tension.
Posts (vertical supports) are used in purlin systems to support the ridge or intermediate purlin. They transfer the load from the roof to internal load-bearing walls or to the floor through sills. The bearing detail of the post on the sill and the connection with the purlin must ensure stability against longitudinal and transverse displacement. Most often, this is achieved using notches: tenons are cut in the post and the purlin, and a mortise is made in the sill, or steel fastening is used – a post base (post holder), which rigidly fixes the element. Several posts connected by a purlin form a longitudinal load-bearing line – a truss, which significantly increases the rigidity of the entire structure.
Struts (diagonal elements) are installed at an angle to the rafter and serve to reinforce it, reducing the free span. They work mainly in compression. The angle of the strut is usually 45-60 degrees. The lower end of the strut bears on a post, a sill, or directly on the wall plate through a notch and additional fastening with a bracket or angle. The upper end is notched into the rafter. This detail requires precise fitting, as the contact area must be sufficient to transfer the force without crushing the wood. For fixation, bolted connections are often used, passing a bolt through the rafter and the strut.
In complex roofs, these elements can be combined, forming multi-support purlin systems or trusses of complex shape. For example, in a mansard (broken) roof, posts are used that simultaneously form the frame for the vertical walls of the attic, and tie beams serve as floor joists. All details in such systems are interdependent, and weakening one of them can lead to redistribution of loads and overloading of other elements. Therefore, during design and installation, it is necessary to strictly follow the design schemes, ensuring reliable connection at each point. The modern approach often involves pre-assembling trusses or entire sections on the ground using metal tooth plates (MTP), which ensures high precision and strength of the details, after which the finished trusses are lifted and installed in place.
Details of Eaves and Gable Overhangs
Eaves and gable overhangs are the parts of the roof that protrude beyond the plane of the external walls. They perform several important functions: protect the facade and foundation from water running off the roof, provide organized water drainage into the gutter system, create architectural expressiveness of the building, and are part of the ventilation system for the under-roof space. The structure of these overhangs is formed by extending the rafters or with the help of additional elements – outriggers (lookouts).
The eaves overhang (horizontal) is formed when the rafter or its extension extends beyond the plane of the wall. The detail for fastening the rafter in the overhang area must provide sufficient strength to resist the bending moment from the weight of the roof and the wind load acting upward on the soffit. If the overhang length is small (up to 50-60 cm), it can be formed directly by the length of the rafter. In this case, the lower end of the rafter, protruding beyond the wall plate, is cut vertically for attaching the fascia board, to which gutter brackets will subsequently be mounted. To strengthen such an overhang, supporting outriggers running from the wall to the edge of the overhang are often installed underneath.
If a longer overhang is required (80-100 cm or more), which is typical for regions with high precipitation or for certain architectural styles, then outriggers (lookouts) are used. An outrigger is a piece of board with a smaller cross-section than the rafter (e.g., 50×100 mm instead of 50×200 mm) that extends the rafter. The detail for connecting the outrigger to the rafter is critically important. It is made with an overlap of at least 50-60 cm and fastened with at least four nails or powerful screws installed in a staggered pattern. Additionally, the connection can be reinforced with wooden overlays or metal plates on both sides. Outriggers are installed after mounting the main rafters; their lower ends are aligned along a stretched cord so that the overhang line is straight. The fascia board is attached to the ends of the outriggers.
The gable (end) overhang is formed by the inclined extension of the sheathing and roofing material beyond the plane of the gable (end) wall. Structurally, it is simpler than the eaves overhang. Most often, it is formed by extensions of the sheathing, which bear on an extended wall plate or on a beam specially extended from the gable (barge board). For rigidity and finishing of the edge, a fascia (wind) board is also attached along the ends of the sheathing extensions. In some designs, the gable overhang is formed by extending the ridge purlin and the outer rafters.
Regardless of the type of overhang, its lower part (soffit) should be finished in such a way as to ensure air intake into the under-roof space for ventilation while preventing the penetration of birds and insects. For this, perforated soffits, soffit boards with a gap, or special ventilation grilles are used. The detail of the soffit attachment to the wall must consider possible shrinkage of wooden walls and thermal-humidity deformations, so fastening is often made non-rigid (through slots or using special profiles). Also, in the area of the eaves overhang, a drip edge is installed to collect condensation from the waterproofing membrane and divert it into the gutter. Correctly designed and executed overhang details not only complete the appearance of the house but also protect its structural elements from premature destruction, ensuring long service life of the roof and facade.
Details for Roof Abutments to Chimneys, Walls, and Dormer Windows
The roof is not an isolated structure; it interacts with other elements of the building: chimney and ventilation pipes, walls (in the presence of extensions, dormer windows), and dormer windows. Abutment details in these places are the most vulnerable in terms of leaks, as the continuity of the roofing covering and waterproofing layer is disrupted here. Therefore, their construction requires special care and often the use of special accessory elements.
The abutment of the roof to a brick or concrete chimney is one of the most complex details. The main tasks are: to ensure the tightness of the joint, organize the diversion of water flowing around the chimney, and comply with fire safety clearances. Structurally, the detail consists of several elements. At the location where the chimney passes through the roofing system, wooden sheathing is arranged with a setback from the masonry of 130-150 mm (fire safety clearance). This space is filled with non-combustible material (most often stone wool). Along the perimeter of the chimney on the slope above it, a so-called “cricket” or “saddle” – a gutter made of galvanized steel or other waterproofing material – is arranged, directing water around the chimney. The main waterproofing (underlayment film or membrane) is brought up the vertical surface of the chimney to a height of at least 50-100 mm and glued with special tape or mastic. Then, a so-called “flashing” – abutment strips (lower and side) – is installed, which are placed under the roofing covering, and an upper one, which is inserted into a groove made in the body of the chimney. The groove is filled with heat-resistant sealant. For flexible shingles, special valley underlayments are used; for metal tiles – ready-made flashings made of the same material.
The abutment of the roof to a vertical wall (for example, to the wall of a higher building volume) is solved in a similar way. A triangular batten is attached to the wall at a height of 200-300 mm above the roof plane. The waterproofing membrane is brought onto it with an overlap onto the wall. Then, an abutment strip (angle) is installed, the upper flange of which is inserted into a groove in the wall or covered with a cover strip, and the lower one is laid on top of the roofing material. The joint is sealed. The roofing covering (tiles, metal) is brought onto this strip.
Installing dormer windows introduces the greatest complexity into the truss system, as it requires cutting out one or several rafters. To compensate for the cut-out load-bearing elements, a reinforced wooden frame (trimming) is created around the window. On the sides of the window, reinforced rafters (doubled) are installed; above and below – horizontal beams (headers) of appropriate cross-section, which redistribute the load to adjacent intact rafters. All connections in this detail are made with bolts or powerful screws, often using steel perforated brackets to ensure rigidity. Waterproofing of the detail is ensured by a special flashing that comes with the window and consists of upper, lower, and side aprons integrated into the roofing system. Correct installation of this detail is critically important for preventing leaks and cold bridges.
All abutment details share a common principle: the waterproofing layer must be continuous and brought up the vertical surface, and water must be diverted from top to bottom, without flowing under the covering. For this, all upper elements overlap the lower ones. Using high-quality sealants, specialized tapes, and accessory elements recommended by manufacturers of roofing materials and windows is the key to the durability and reliability of these complex connections.
Sheathing and Counter-Batten Details
Sheathing and counter-batten are the elements directly bearing the roofing covering and forming the ventilation gap underneath it. Although these elements seem simple, the details of their attachment to the truss system and to each other play an important role in ensuring ventilation, the proper operation of the insulation, and the durability of the entire structure.
Counter-batten is battens with a cross-section usually of 30×50 mm or 40×50 mm, which are nailed along the rafters on top of the waterproofing membrane. Its main function is to create a ventilation gap between the membrane and the sheathing for free air circulation, removing moisture from the insulation. The detail for attaching the counter-batten is simple: the battens are nailed or screwed to the rafters over the membrane laid with a sag. The fastening must be reliable to withstand possible loads during roof installation and operation. It is important that the counter-batten is continuous along the entire length of the slope from the eaves to the ridge, ensuring unobstructed air passage. In the areas of valleys, around pipes, and other obstacles, the counter-batten may be interrupted, but then ventilation channels must be provided by other means.
Sheathing is nailed across the counter-batten (and, accordingly, across the rafters). Its type (solid or spaced) and pitch depend on the type of roofing covering. For soft shingles, flat slate, and roll materials, a solid base made of moisture-resistant plywood, OSB-3, or edged boards laid with a gap of 3-5 mm is required. For metal tiles, corrugated sheets, and natural tiles, spaced sheathing made of battens or boards is used. The detail for attaching the sheathing to the counter-batten is also done with nails or screws. A critically important point is the alignment of the sheathing plane. All battens or boards must lie in the same plane, without local protrusions and dips, otherwise this will affect the appearance of the roof and may lead to a breach in the tightness of the covering. For this, a template or stretched cords are used during installation.
Special requirements apply to sheathing details in areas of increased load: on eaves overhangs, in valleys, around penetrations. At the eaves, a solid deck usually 40-60 cm wide is made for reinforcement and convenience of installing the drip edge and the first row of covering. In the valley under metal roofs, a solid wooden gutter is often arranged for laying the valley underlayment. In these zones, sheathing fastening should be more frequent. It is also important to ensure reliable fastening of the sheathing at the ridge and hips for subsequent installation of ridge and hip elements.
Sheathing and counter-batten details are closely related to the ventilation system. Joints of counter-batten or sheathing should not block ventilation channels. This is especially true for the ridge area, where free air exit must be ensured. For this, the upper ends of the counter-batten do not reach the ridge beam by 30-50 mm, and the sheathing is laid with a gap. Modern ventilated ridge systems are mounted directly on this gap. Thus, competent execution of seemingly simple sheathing and counter-batten details lays the foundation for the proper functioning of the roofing system, effective ventilation, and, ultimately, the long service life of the entire roof.
Errors in Constructing Wooden Roof Details and Their Consequences
Incorrect design or installation of wooden roof details is the main cause of problems during operation: leaks, deformations, loss of load-bearing capacity, and even collapses. These errors are often systemic and related to insufficient qualifications of the performers, attempts to save on materials or time, ignoring building codes and manufacturer recommendations.
One of the most dangerous errors is incorrect attachment of the wall plate to the wall, especially in houses made of aerated concrete or porous ceramic. Using ordinary mechanical anchors without a reinforced concrete belt or using insufficiently long and thin studs leads to the fastening being pulled out of the fragile material under load. The consequence is displacement of the entire truss system, opening of the ridge detail, deformation of the roof and walls. Another common error in this detail is the absence of waterproofing between the wall plate and the wall, leading to rapid rotting of the wood in the area of maximum load and moisture.
In the detail of rafter bearing on the wall plate, a typical error is rigid fastening of the rafter in a non-thrust system (for example, rigid connection with angles without the possibility of displacement). This creates unaccounted thrust, which tends to push the walls apart. In masonry houses, this can lead to cracks in the walls; in wooden houses – to disruption of the log house geometry. The reverse error is insufficient fastening in a thrust system, when the rafter simply lies on the wall plate without notching and reliable metal fixation. Under strong wind or uneven load, such a rafter can slide off.
In the ridge detail, the following shortcomings are common: absence of a rigid connection between the rafters (when they are simply nailed to the ridge purlin and not connected), leading to divergence of the slopes under load; using only nails without plates or bolts for connecting rafters – such a connection works in shear and can loosen over time; incorrect geometry of notches, weakening the rafter cross-section at the most stressed point. Consequences – ridge sagging, formation of a “hump” or “boat” on the roof.
Errors in constructing details with tie beams, posts, and struts are most often related to misunderstanding of their work. For example, a tie beam working in tension is connected using nails, which perform poorly in withdrawal. Or a strut is notched into the rafter too shallowly, leading to crushing of the wood and loss of the strut’s effectiveness. Incorrect placement of these elements (for example, a tie beam placed too high, which cannot effectively absorb thrust) also negates their function.
In overhang details, a typical error is saving on fastening outriggers (just a couple of nails), which can lead to the overhang tearing off under the weight of ice. The absence of ventilation gaps in the eaves soffit becomes the cause of air stagnation in the under-roof space, moisture condensation, and rotting of wooden structures. In abutment details to chimneys, the main error is attempting to seal gaps with polyurethane foam, which is not a waterproofing material, deteriorates under UV radiation, and creates a false sense of tightness. Failure to comply with fire safety clearances around a chimney is a direct fire hazard.
Prevention of these errors lies in the mandatory availability of a competent truss system design, performed considering all loads and features of the wall material, using quality kiln-dried lumber, using modern reliable fasteners (perforated plates, bolts, screws, post bases), as well as involving experienced specialists familiar not only with carpentry techniques but also with the principles of structural behavior. Regular control at each installation stage will help identify and correct shortcomings in time, guaranteeing that the wooden roof will serve reliably and for a long time.