A dormer window on the roof is provided primarily to provide an attic (mansard) room with lighting and ventilation. In addition, dormer windows are an important component of the appearance both separately of the roof of the house, and in the aggregate of the entire structure.
Design features of dormer windows
The most common solution for the installation of dormer windows are triangular structures with steep roof slopes.
The main distinguishing feature of this style is the lack of penetration of the gable wall of the dormer window into the roof. It is located in the same plane with the outer wall of the house.
In addition, this type of dormer window is always mounted exactly on the same axis as the window below it. Thanks to this, the windows on the roof do not look alien, but are perceived as one with the entire facade of the building.
However, such a design of the dormer window, due to the significant steepness of the roof slopes (about 64 degrees), practically does not increase the useful area of the attic room.
The main advantage here is the attractive appearance of the building, as well as the originality of the layout of the premises under the roof.
The significant height of the space under the roof with a sharp top makes it easy to place large-sized dormer-type windows on the gable. At the same time, in the decoration of the attic, it becomes possible to use details reminiscent of the vaults of cathedrals.
Among other things, due to the fact that the roof of the triangular dormer window descends to the main roof of the house before the formation of a groove, there is no problem of waterproofing the joints of the side walls with the roof, which makes it much easier to trim and seal both the roof windows themselves and the main roof Houses.
Dormer window frame device
To build skylights, you need to start with the device of their frame.
And before the construction of the window frame, first they arrange the frame of the roof of the house:
- Perform pediments.
- Mount the ridge beam and all rafter legs.
- At the locations of the dormer windows, openings are provided between the mounted rafters. At the same time, the rafters that frame these openings are double and even triple, since the load on such rafters is assumed to be much greater in comparison with all other rafters of the main roof.
A do-it-yourself skylight according to a standard project involves supporting the gables of the dormer windows with side walls 1.5 m high, which extend from the outer wall of the house inland.
In turn, the frames of these side walls rest on the beams of the ceiling, which is located under the dormer window.
For this reason, immediately after the assembly of the truss structure of the main roof, the frames of these side walls are first mounted, and then the racks and crossbeams of the gable frames of the dormer windows, which have a horizontal position, are already tied to them.
Further, the process of installing a window on the roof continues according to the following scheme:
- Since the gables of the triangular dormer window are located in the same plane with the main wall of the house, the lower ends of the rafter legs adjacent to them are cut off flush with the wall sheathing.
- At the height of the ridge beams of the dormer window, provided for by the project, lintel beams are mounted between the twin rafter legs. It is unacceptable to make cuts or tie-ins that can weaken the rafter beams. For this reason, the use of overhead metal brackets is recommended for fastening the ends of the jumpers.
- Before installing the ridge beams of the dormer windows in place, the verticality of the gable frames of each dormer window is re-checked.Next, install and nail the ridge bars into place.
- Cut out a pair of rafters according to the template and install them on the gables of each dormer window for the roof.
- The frames of the gables are sheathed with sheets of construction waterproof plywood. The sheathing of the gables is placed strictly flush with the sheathing of the wall of the house.
Installation of grooves in the upper part of the dormer window
The construction and method of assembling the roof of a triangular dormer at first glance differs little from the manufacture of a conventional roof of a multi-gable type.
However, the difference is noticeable. The slopes of a multi-gable roof usually have the same slope. At triangular dormer windows, the roof slopes of which have a slope of 64 degrees, the connection with the slopes of the main roof, which has a slope of 40 degrees, occurs with the formation of completely non-standard grooves (valleys).
For this reason, to simplify the task, the lower and upper parts of the groove are made in two different ways.
In the upper part of the roof of the dormer window, which should look like a cathedral arch from the side of the attic, a structure with slanted rafters is used, on which shortened rafters (spreaders) rest at an angle of 64 degrees.
For mounting this part of the structure, such as double pitched roof, first of all, determine the dimensions of the grooved rafter beam, the length of the beam, as well as the angles of mating with the side wall and the ridge beam.
The further process of how to make a skylight is as follows:
- To begin with, with the help of a plumb line or a long level, the position of the center of the intersection of the groove with the beam of the roof ridge is transferred to the floor.
- After that, using a ruler, draw a line from the obtained point to the corner of the side wall, and then the line of the ridge beam. Both lines, from the point of view of geometry, represent the projection of the rafter beam of the ridge beam and the groove onto a horizontal plane.
- The angle obtained between them is measured directly on the floor with a square. At this angle, the front end (lower) of the truss beam of the groove is cut down in order to accurately mate it with the side wall of the opening.
- By stretching the cord from the ridge beam to the corner of the side wall, the angle of the cut of the upper end of the rafter beam is determined with a square. By measuring the distance between these points, the length of the gutter truss beam is determined.
- After that, the projection line of the rafter beam is transferred to the upper beam (located on the side wall) and the length of the lower reference cut of the beam is measured.
- After taking measurements at the installation site, the beams mark the workpiece, cut it along the length, cut the end edges at angles of 18 and 72 degrees, and mount them in place.
Advice! Each skylight requires the manufacture of a pair of similar mirror-symmetrical beams. To make shortened rafters, it is advisable to make a universal template, according to which then cut out the required number of blanks.
The device of the lower part of the dormer window
In this part of the window, in which the inner part soft roof hidden by the side walls and not visible from the inside, a simplified method of constructing a groove is used.
On top of the roof sheathing of the house, a groove beam is nailed, on which the ends of the rafters of the gable roof of the dormer window are emphasized.For this reason, this part of the work is carried out upon completion of the sheathing of the main roof of the house with sheets of waterproof construction plywood.
At the same time, to increase the strength, sheathing sheets are laid, starting from the side walls of the windows.
The position and dimensions of the support beam for the rafters are determined quite simply:
- pull from the end of the rafter beam and to the outer edge of the pediment a chalked cord;
- beat off the chalk line with this cord;
- measure the length of the line and cut out a blank for the support beam;
- its lateral outer edge is cut off at a bevel at an angle of 64 degrees;
- nailed exactly along the line marked with chalk.
The blanks for the rafters of the lower part of the roof slope of the dormer window are cut out according to a single template, cutting only the ends to the required length when mounting them in place.
The final step in resolving the issue of how to make a window in the roof is sheathing the roof of the dormers with sheets of construction plywood.
The process is usually started from the top of the ridge, especially when working with such steep slopes. Having reached the very top, the work is carried out with a whole plywood sheet, precisely orienting it along the upper ridge edge.
Measure and adjust the rest of the corner fragments, located below.
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