Dormer window on the roof: design and drawing

Vadim
7786 0 2

Vadim November 1, 2017

A beautiful dormer window on the roof is not only an effective element of roof design, but also a rather useful structure, because the more such windows in the attic, the better the natural light will be. Next, you will find out what types of similar structures are divided into, and how they differ from each other. And for the DIYers, I’ll tell you about assembling the 2 simplest options with your own hands.

Dormers can decorate any roof.

What functions does the auditory window perform, classification

A dormer is a glazed window frame built into the roof in one way or another. If compared with a regular window, the size of the auditory window is usually much smaller. The point here is not for the home owner to have a panoramic view of the landscape, although this is possible.

The direct tasks of the window include:

Supplying sunlight to the attic or attic area, which helps reduce dampness and the development of mold fungi;
Providing additional ventilation;
Allowing access to the outside of the roof if cleaning or repair is necessary.

Classification of dormer windows by shape
According to the shape of the external design, dormer windows are different, but they all belong to one or another type of structure, from the classification list:

Made in gable side wall;
A constructive solution called dormer;
Antidormer design;
Inclined, made on the same plane as the roof;
Design of the "rooflight" type.

A short excursion into history

For the first time, dormer windows began to be used in the architecture of medieval Europe, becoming especially widespread during the Renaissance (XV-XVI centuries). In Gothic buildings they were traditionally decorated with rich stucco or carvings, turrets, side pilasters and false columns. Structurally, they were a continuation of the wall of the building’s facade, and were located parallel to it. Visible from afar, such structures in an exquisite decorative frame became a real calling card of the entire building.

The construction term “dormer window” is used only in Russian, having no analogues in other countries. Thus, in Europe, windows in the roofs of buildings, since the Middle Ages, have traditionally been called “lucarnes” in the French manner.

Dormer windows - lucarnes

In England and the USA, the name dormer or skylight is more common - attic, skylight. Where did this rather strange name come from in our language? There are two versions of the origin of this name. One is given in V. Dahl’s Russian language dictionary, and the other is associated with the legend about the construction of the Moscow Manege.

The great Russian ethnographer Dal in his dictionary gives the following interpretation of this architectural term. “A hearing window made in the roof.” The word “rumor” previously in colloquial Russian also had the meaning of “vent”, “ventilation hole”. Dahl is inclined towards this interpretation, because “there is nothing to listen to in the attic through this window.” The legendary version associated with the construction of an arena in Moscow is also widespread. This building, now located on Manezhnaya Square of the same name, was erected in honor of the five-year anniversary of the expulsion of Napoleonic hordes from Russia.

As you can see, the playpen has many dormers

Initially, the Manege was called Exertsirgauz, and was intended for drill training of troops, as well as for reviews and parades during bad weather. The construction was initiated by the victorious Emperor Alexander I personally. The construction of the building was completed in a year, and the autocrat had to personally accept the building. But by the time Alexander visited the Manege, a big problem had occurred: the suspended ceilings, richly decorated with plaster stucco, were noticeably deformed for some reason. This did not escape the meticulous gaze of the emperor, who ordered the cause of the defect to be identified and eliminated.

The reason turned out to be simple: deformation of the rafters made of larch. The metal roof of the Manege heated up in the summer sun, and after it, the attic space, made without vents, also heated up. The civil engineer Slukhov was entrusted with correcting the situation, who found a way out in the device along the entire roof of two rows of ventilation windows. Since then, roof windows have become an integral part of the structures of all large buildings, especially those roofed with metal. And in Russian architecture, they are named after the engineer Slukhov, and the name “auditory” is supposedly assigned to them.

More information about the history of dormer windows:

Different types of dormer window schemes

Depending on how the window frame is attached to the main frame, there are several types of dormer window designs. Each type has its own design feature and installation rules.

Types of dormer windows

There are simpler and more complex window designs. Some of them are very difficult to implement on an already finished roof without major alterations to the latter. Therefore, it is more advisable to install dormer windows at the design stage of the building.

In the gable wall

By gable we mean the wall that every house with a gable roof has, namely its upper end part in the form of a triangle limited by slopes. This is one of the simplest dormer windows, during the implementation of which the roof itself is not subject to transformation. The design is a frame built into a wall opening. Most often, its shape at the top repeats a triangle, but this is not necessary.

Dormer design

A complex structure that is completely located outside the roof slope (namely, above it), thereby increasing the volume of attic space. During implementation, the difficulty arises in the correct connection of the waterproofing of the main roof and the dormer, in order to avoid leaks in the joint area. From an aesthetic point of view, this type of window looks the most beautiful. There are many modifications, which makes it possible to harmoniously place it on any roof.

Antidormer

This is a structure that is the opposite in appearance to a dormer, that is, it does not protrude beyond the roof, but hides inside the attic, thereby reducing it by the amount of its own volume. To organize an antidormer you need a minimum of material; here it is easier to connect its waterproofing with the main one. The only disadvantage of such a window is that it does not create a good decorative effect.

Mansard type - inclined

To organize a dormer window in your home, there is no need to add a complex frame, as is done when installing a dormer. The dormer inclined window is installed in the same plane of the roof, resting its frame on the rafters and additional lintels. The difficulty in this case is the mechanism of opening and closing the frame itself, so they are quite expensive. Dormer windows can be either metal-plastic or made of laminated veneer lumber.

Window - “rooflight”

The name itself suggests that this design allows light into the room in the best way. This effect is observed by making the opening completely glass in a frame without jumpers and, as a rule, of large dimensions. This type of construction is used on the roofs of factories, production areas and for lighting public buildings.

Self-assembly options

It is advisable to plan and arrange dormer windows at the stage of assembling the roof truss system.

If the roof is completely assembled, but you are determined to make a window in it, my advice to you is to call a professional.

A few words about standards

When constructing such structures, according to the law, one must be guided by GOST 1250681, as well as SNiP II-26 and SNiP 21-01, but these standards are relevant for the construction of administrative buildings. As for private houses, almost all the instructions written in the documents are more advisory in nature:

In particular, it is not recommended to install a dormer window in the roof plane closer than 1 m from the gable wall;
If the roof slope angle is less than 35º, then it is better to limit yourself to a window on the pediment;
In cases where several windows are installed in a row on one slope, the distance between them must be at least 800 mm;
The lower cut of the window frame should be at a distance of 1 m from the attic floor.

Normal natural light is ensured if the window area is 14–16% of the floor area in the attic. But according to regulations, the area of windows should not exceed half the floor area in the attic.

Option No. 1: the simplest single-pitch design

Illustrations	Recommendations
	Framing the structure. The first to install a rectangular frame in the rafter system of the slope: Rafter legs that get in the way are simply cut to the width of the opening; Then horizontal bars are placed on top and bottom. For these purposes, it is best to use the timber from which the rafter legs are made.
	Support racks. The extreme vertical posts are made of 2 bars. One bar is nailed to the side of the rafter leg, and the other is placed on the rafter leg, plus the bars are fastened together. I recommend taking bars with a thickness of 50 mm or more. Read also: How to replace windows in an old country house? We tell and show Horizontal roof rafters are nailed to the vertical posts. The angle of inclination of the rafters should be from 5º.
	We knock down the frame. The rest of the frame is knocked together, as shown in the diagram on the left, from the same bars. It is not worth installing intermediate posts and upper rafters too often; a step of 50 cm will be enough. Don’t forget, you still need to lay insulation between these bars, and each block is a cold bridge.
	Roof frame. Since our roof is flat, the roof frame is made reinforced, from 2 rows of cross strips. The lower support frame under the window can be mounted as desired; I recommend raising the window above the roof by at least 100 mm, this way you will protect it from snow and water.
	Sheathing the frame. For external cladding, OSB or waterproof plywood with a thickness of 10 mm or more is used. To insulate the main roof, dense slabs of mineral wool are usually used. In the frame of the viewing window, the vapor permeability of the insulation is not so important, so foam plastic or EPS can be used here. The roofing material used is the same as on the main roof, and the side walls can be sheathed with galvanized iron and painted in the color of the roof.

Option number 2: triangle

The triangular structure is installed at the stage of arrangement of the main rafter system. Although our final shape is triangular, the exit opening is made in the same way as in the previous version, rectangular.

In a triangular structure, the exit opening between the rafters is made rectangular.

Next, a vertical face truss is installed, with the edges of the triangle extending beyond the main opening. The top of the truss should be flush with the horizontal beam of the opening.

Simultaneously with the installation of the front triangular truss, the ridge beam is installed. It connects the floor beam of the opening with the vertex of the triangle and is located strictly horizontally. In this case, 100x50 mm timber is sufficient.

Diagram of a triangular rafter system.

After this, a triangle is arranged on the roof plane. You need to connect the ridge beam attachment point in the opening to the edges of the face truss. The rafter legs of the window frame will rest on these bars.

It is better to sheathe the frame with OSB sheets.

After covering the front truss with OSB sheets or waterproof plywood, a small frame is stuffed on the sides for the “overhang” of the roof. At the last stage, everything is covered with sheets and you can begin installing the roofing, insulation and finishing.

The observation window and the roof roof are sheathed with the same material.

Design features of commonly used dormer windows

The most common designs of dormer windows are gable windows and two types, which are of the dormer type with a pitched and gable roof. With the gable wall everything is very clear. There is no complicated design here. At the stage of constructing the building box, an opening is simply left in the triangular part of the wall for the frame with a lintel at the top, as required during construction.

Roof structure with dormer windows

Dormer shed is characterized by the fact that its roof has a gentle slope and can never pass at the angle of the main roof. The frame itself is limited by a frame, where there are walls on the sides, and a front wall into which it is inserted. The easiest way is to make the front wall as a superstructure over the load-bearing wall; this will eliminate the need to use lightweight material in the structure. A pitched roof should have a good overhang on all sides.

A gable dormer can be simplified, when the roof frame encloses a window frame, and more complex, when the gable roof hangs over vertical walls protruding from the main roof. It is shaped like a small house on the roof. In both cases, the articulation of the main roof with the dormer window is carried out using a valley.

Getting Started

As mentioned above and as can be seen from the drawings below, the most popular design of a dormer window on the roof is the dormer. Therefore, in most sources, the description of the construction of an attic window involves the construction of exactly this type of dormer opening.

Installation of the roofing “house” is carried out only on already installed load-bearing rafter “legs”. In its design, the dormer opening resembles the structure of a roof, only in miniature. It has its own rafter system, sheathing, and, with a gable roof, a ridge.

Cross-sectional diagram of an attic dormer

As for the inclined roof window, inscribed into the surface of the roof, its construction does not require the construction of a separate frame. However, additional requirements are imposed on the quality of the window block. Since one of the purposes of the dormer opening is to illuminate the attic, the owner should take this into account and plan a dormer on the south side of the roof. At worst - in the east or west, but most importantly - not in the north.

What requirements are taken into account when designing?

The most important requirements that need to be taken into account when designing a roof with a dormer window are the requirements of SNiP. Compliance with building codes and regulations will allow the structure to serve for a long time without the risk of destruction:

When installed permissibly, the roof slope must have a slope of at least 35 degrees;
The position of any superstructure regarding the distance from the external walls is necessarily regulated;
The minimum size of the frame sashes should be within 0.6 by 0.8;
The plane of the window facade, where a hip roof is used and a quadrangular opening cannot continue the wall of the house;
Do not overload the roof structure with a large number of additional heavy elements.

Construction of the dormer window rafter system

What should the drawing contain?

The implementation of a window begins with a detailed drawing of the drawing. The drawing provides the general dimensions of the structure, the dimensions of individual elements, designated angles, and the name of each part of the structure. The notes must indicate the materials used, the number of parts, assembly steps with detailed explanations. Assembly points that are difficult to understand should be described in footnotes.

Drawing of a dormer window

How to properly install a dormer window - technology

To install a gable-type dormer on the roof, you need to assemble a truss structure, for this:

Installation of a dormer window

The ridge beam of the window is removed from the base of the roof, resting it on a temporary support;
From the same point in the roof plane, support beams under the dormer rafters are attached to the roof rafters;
In the place where the support beams diverge between adjacent rafters of the base, a wooden jumper is installed;
Rafters are lowered from the ridge beam to the plane of the main roof, securing the edges to the support beams;
A window frame is attached to the outer rafters of the dormer, the lower part of which is fixed to the lintel between adjacent rafters of the main roof;
At the point where the slopes of the window and roof meet, a valley is attached;
Organize thorough waterproofing;
For greater reliability, props are placed under the dormer, resting them on the floor of the attic.

Arrangement of dormer windows - recommendations

The best lighting is provided by an opening located higher to the ridge;
For the frame, only high-quality wood treated with fungicides is used;
When installing a window on a finished roof in the installation area, carefully remove the sheets of waterproofing material;
Open the cake so that you can get to the frame;
All additional elements are attached to the roof rafters without insertion, using fasteners;
To avoid leaks at the joints of the waterproofing, the joints are covered with sealant.

Diagram of the dormer window

Device

Dormer windows have different shapes. A gable or single-pitch roof is installed over such a structure.

The single-pitched variety is the most common. Snow falls from it towards the glass unit, which can cause its destruction. Therefore, the roof slope must be made larger than in other options. Sometimes it looks ridiculous, since her “hat” stands out significantly from the general background.

It is more difficult to assemble gable roofs, because it is necessary for the ridge to be of increased strength. But they cope with the function of drainage much better, and they look neater than single slopes.

With the modern level of technology and variety of materials, every owner can afford other geometric shapes.

Device classification

They differ in the number of slopes and general shape:

single-slope, double-slope, four-slope (hip);
flat (French), as well as arched;
triangular and trapezoidal.

Glazing can be done partially; ventilation grilles can be installed as an addition. Designs can be made without glass at all; it is completely replaced by convection blinds.

Architectural features

Triangular roof options are especially popular; in terms of vertical projection parameters, they are close to equilateral triangles with slope angles approaching 30°. Typically, their gable is flush with the gable of the building.

For your information! They are located symmetrically to the main window openings of the building. This allows the triangular shape to harmonize with the ensemble of the entire structure.

The main advantage of this option is that the triangular design completely solves the issue of sealing the entire element: the ridge is reliably protected, and there are no insulation joints at the base. Water immediately enters the drainage gutters because the window is formed flush with the common gable.

We recommend: Replacing the high pressure hose

Design and installation

The construction scheme is simple; for a beginner, only the names of the structural elements of the roof can cause difficulty. The structures have their own frame and are sewn to the frame of the main roof.

Gable frame

It is designed in such a way that the window is located between the rafters of the roof of the house. In places of contact they are strengthened: double rafters are formed.

Construction is regulated by the rules of GOST 1250681:

Load-bearing rafters should not extend beyond the plane of the building.
When installing and fastening, it is unacceptable to cut into the base of the roof, i.e. cutting is prohibited as this reduces the strength of the main structure. Fastening is carried out using nails or self-tapping screws of the required length.
The pediment of the windows must be strictly vertical, in one common plane.
In accordance with the dimensions, two rafters are selected to form a gable triangle, which are attached to the ridge.
The resulting frame is covered with moisture-resistant plywood or sheathing, after which the finishing coating is laid.

Installation of a dormer window on the roof for beauty and more