Table of Contents
To find out everything that is connected with construction of roof, it is necessary for blueprint stage. Most of builders has the most popular type of roof classical gable roof, that is roof with two slopes.
Why this option? Because at gable roof number of indisputable advantages is had:
- resistance to wind and snow loads;
- fast running off of rainfall;
- attractive type, possibility of use of set of design receptions;
- rather simple design;
- possibility of independent construction;
- opportunity to equip in subroof space premises – penthouse;
- small material consumption.
Nevertheless, construction of gable roof the hands means possession of certain skills and knowledge which it will be difficult to build such roof without. Besides, even prior to construction, it is necessary to carry out exact calculations of roof. On it we will stop separately after we describe the main stages of construction.
Materials necessary for mounting:
- Eaves board with sizes of 150х50 mm;
- Wooden bar about the section of 150х150 mm;
- Fixing material: nails, screws, bolts, self-tapping screws;
- Materials for the device of roofing pie (waterproofing, vapor barrier, heater);
- Roofing materials (slate, professional flooring, metal tile etc.).
The design of gable roof represents two surfaces (two slopes) located under certain corner to each other with one line of contact. Bottom edges of slopes lean on house walls. Side fastenings are called pediments, and the line of contact of slopes – the fad.
Length and width of slopes, corner under which they are located, length of overhang of roof can be the most different and depend only on the project.
Gable roofs can be:
- with suspension post;
- with inclined rafters;
- with different tilt angles of slopes;
- with different sizes of eaves overhang.
The simplest constructive option means that under roof there will be cold attic intended for economic needs. But this space can be used and is more practical and to equip in it premises. In this case the gable broken roof can be constructed, in slopes windows are mounted or the extension is added. However it is necessary to consider that similar projects are considerably more expensive because demand high-quality isolation, careful warming and, respectively, bigger expense of materials.
The design of double-pitch roof represents the supporting girders covered with furring on which the roofing material fastens. Rafters and furring are carried out from wooden bars and boards among themselves fastened with normal nails, bolts, and sometimes metal special feature connectors. As rafters can serve and the metal sections allowing to cover big flights without use of additional has flown down also knee braces. Such designs prepare according to drawings industrially and have high accuracy that allows to make mounting by the worker who does not have high qualification. However they rather heavy, and it puts the big pressure upon walls of the building and complicates raising of designs.
The device of double-pitch roof rather simple, allows to adapt it for features of the specific house for performance of additional functions. For example, the fad can be extended, as a result longer slopes going far beyond side walls perform functions of roof of additional constructions, verandah or garage.
For construction only the pine wood is chosen. Rails, boards and bars are applied. Material should not be wet (humidity within 20%). Otherwise the high content of moisture can lead to deformation of the main nodes and damage of roof. Also wood materials have to be antiseptic.
Mounting of gable roof
Work takes place in three stages:
- installation of load-carrying structures – beams;
- mounting of furring;
- flooring of roofing materials.
Installation of roof begins with mounting of transfers (floor beams). At first the bar keeps within – strictly on drains of walls, durability of all design depends on the accuracy of laying. Beams keep within so that the roof mounted on them acted not less than on 40 cm from edge of wall – it will provide reliable protection against rainfall and wind.
Then on all area of the house on floor beams the eaves board fastens. If it is not going to use attic-floor room under premises, boards of 50х150 mm are used, the big thickness of boards otherwise is chosen. Further they can be used also as floor of attic room and as support for penthouse racks. The board is fixed by nails or self-tapping screws.
After fixing of racks there comes the turn of rafter system. First of all, pediments are established. This continuation of end walls of the house which is smoothly overflowing in roof triangle. Points on which the fad will lean become top of these triangles. On upper binding of pediments are exposed on edge of board of 150х50 mm.
It is necessary to remember that if arrangement of attic room is planned, the rafter design has to be strengthened by binding and fixing of the eaves board laid by edge up. These actions are necessary for strengthening of design for reason of safety of owners of the house.
Also it is necessary to pick up correctly material for rafters. Beams have to be equal and not have knots. For rafter “legs” use high-strength firwood.
Naturally, material for rafters should be selected correctly too: equal beams without cracks and knots. As a rule, for rafter “legs” high-strength wood of pine is used. And here the overwound wood is not recommended to be applied — in order to avoid formation of roughnesses at the roof device.
Rafters of roof have to be as it is possible are more densely attached to pediments and densely adjoined to them. The lower parts of boards are for this purpose sawn off. It becomes as follows: the board edge keeps within on pediment part, in places of contact with transfer line on which it is made is drawn has spent on drink. The “thrust bearing” mown under necessary corner which will densely lie on the transfer plane on all length turns out. Also the upper part of rafters is in this way cut off. In result and in upper point they densely adjoin to each other.
Rafters fasten to the basis self-tapping screws or nails, and their upper part besides, is fixed by metal level or corner. Finally upper elements of rafter design are fixed by means of crossbar. Riegel at the same time acts also as ceiling overlapping of penthouse. To give to rafters still big rigidity, atop they can be fixed by metal pads.
After strengthening the vertical position of pediments is surely checked. And their tops which have to correspond to one level. Final fixing with nails, brackets and soft wire is made only after check of vertical position of pediments and alignment of level of tops of rafters.
When process of installation of rafters comes to an end, for prevention of their sagging and increase in rigidity the design amplifies knee braces. Knee braces fasten one end to rack, and another to the middle of foot of a rafter. Before beating knee brace to foot of a rafter, in this end of knee brace the groove is cut.
After that on rafters furring from normal rails with a section of 25х25 mm keeps within. For prevention of damage of roofing material after drying of timber. The type of furring its step depends on the chosen roofing material. Mounting of furring is made with ledges over pediments on 300-400 mm.
On it works on construction of framework of roof can be considered finished, further actions concern already roofing materials.
Before to lay directly roof, it is necessary to prepare preliminary layers: vapor and waterproofing, heater. This stage is also connected with calculations, the weight of roofing pie has to be counted so that the roof maintained both the deadweight, and weight of the materials stacked on it, and additional loadings in the form of snow, wind and rain.
Additional layers are mounted in load-bearing framework therefore are called frame pie. This “pie” at the correct installation increases roof life cycle, keeps warmly at home, reduces the expenses spent for heating, protects the room from moisture penetration. All layers are connected with each other, but fulfill own purpose. The mistakes made when mounting layers lead to reduction of life cycle of roof and all house and to lowering of utilization properties.
Correctly collected roofing pie will not allow emergence of many problems:
- will reduce heatlosses;
- will not give the chance for emergence of condensate;
- will exclude possibility of sleet and icicles.
Heater – is used for reduction of heatlosses. Effective heat insulation of roof is one of the main requirements imposed to qualitative residential buildings. Availability of heater is especially important for the roofs provided under inhabited space. In this case heater not only interferes with emergence of condensate and minimizes heat waste through roof, but also reduces them on the floor located below. As a result of expense for heating 20-50% decrease, in hot season the roofing space heats up less, and the room receives additional sound insulation.
Heater between rafters is established. Necessary thickness in most cases is 250 mm. Material selection remains for the builder. Now the market offers set of both the widely known, and new materials differing in quality, weight, convenience of mounting and the price: beginning from glass wool and polyfoam and finishing made foam poliestiroly.
Vapor barrier and waterproofing
The vapor barrier interferes with hit of steam in heater from intra house rooms. For its device the film from the inside is attached to the bearing wooden elements. Fastening is made by the mechanical stapling machine with brackets or galvanized nails with flat hats. The film needs to be stacked with overlap in 10-15 cm, both down, and across. Among themselves separate strips of roll have to be hermetically fastened by connecting tape. The ceiling of premises should not concern Paro of barrier therefore after installation the film is fixed by rails.
The waterproofing, on the contrary, acts as barrier to condensate, roofing materials formed on internal surfaces. The film is fixed over rafters horizontally. Width between rafters should not exceed 1.2 meters. Sagging of hydroprotective film to 2 centimeters is admissible, but it should not adjoin to heater. Therefore before the roofing material is mounted, after fixing of film on rafters, are beaten Contras of rail.
One more obligatory way of fight against dampness – ventilation of space. Removal of humid air comes from subroofing space or by means of natural draft, or thanks to special ventilation valves. Air has to pass through the space formed by constructive parts — furring and counterfurring. Arrangement of vent system demands additional expenses, but they are justified as considerably prolong roof life cycle.
The attic-floor room is often used for placement of different ventilating ducts and pipelines.
Roofs of this kind can be established not only by means of wooden rafters and roof frames, but also elements made of steel concrete or steel. However, mounting of such designs is connected with set of difficulties and independently it will not be possible to construct gable roof of them.
Gable roofs do not limit builders in the choice of roofing material. The duo-pitch roof can be made of flexible tile, metal tile, galvanized and brass plate, slate, professional flooring, wavy and bituminous leaf, natural tile, etc. Material selection depends on wishes of owners of the house, and mounting in each case has to meet the separate requirements.
How to calculate roof
Let’s return to question of calculation of roof. Construction demands the ultimate accuracy and certain advantage. Some of them can be carried out by means of the electronic calculators offered by the construction websites. But really exact calculation can be made only “manually” taking into account features of specific object.
The concept of calculation of roof includes height, bias, the area, amount of necessary materials. Digits are necessary not only for compliance of the project documentation and theoretical calculations. They help to understand how many what material is required. Besides, accounting of features of slopes will help also with selection of material for roof.
It is much simpler to make calculation of gable roof, than calculations of the majority of other designs.
Calculation of tilt angle
Without appropriate bias atmospheric precipitation will gather on roof. Calculation of bias gives idea of lifting height of the fad and allows to calculate amount of necessary material.
The tilt angle can make from 11 ° up to 70 °, however, the inclination higher than 45 ° is inexpedient. The big bias is not necessary in warm and arid climate. And areas with snow and cold winters demand big inclination. The corner in 45 ° saves roof from snow loading, however strengthens wind pressure. In this case furring and rafters need strengthening. The bigger bias demands also bigger quantity of roofing material.
In many respects this indicator depends also on selection of material for roofing works. For example, the metal roof or rolled materials demand bias at 15-27 °.
In the provided table the bias is shown in degrees and percent, and the coefficient of raising of roof which equals to raising of the fad on height of 1 meter is given in the last column.
Calculation of height of roof
Example of calculation:
The house 8 m wide with bias of roof 40 °. Half of width (4 m) is multiplied by the fad coefficient taken from the table. For 40 ° it will make 0.839.
We receive 0.839*4=3.356.
Raising of the fad of such roof will be 3.356 meters.
Calculation of roof area
Importance necessary for clarification of quantity of roofing material. Also both selection of water waste system, diameters of rain water pipes and trenches depends on tilt angle and on roof area. The slope of 50 sq.m will manage trench which diameter is equal to 125 mm. And the area of 100 sq.m will demand trenches with a diameter of 150 mm. Rain water pipes are calculated as follows: on each 10 m of trench – one rain water pipe.
If the roof consists of two equal parallelograms, calculation of its area is possible. Height of parallelogram (a) is multiplied by width (b), then the received digit is multiplied by 2 for obtaining value of total area:
ab + ab = 2ab = S
It is necessary to consider that material needs to be bought with stock as its sheets always keep within with an overlap. The size of overlap depends on the chosen material. It is important to remember that calculations are conducted not on walls, and on eaves overhangs.
It is impossible to neglect such calculations, it leads not only to excess expense of means, but also to the fact that the roof can be damaged or destroyed already during operation of the house. It is quite possible to make calculation of duo-pitch roof independently whereas more irregular shapes of roofs demand professional approach.