- Roof opening
- Dormer construction
- Difference between horizontal and sloped glazing
- Window block insulation
- Securing the frame and finishing the abutments
In the installation of attic glazing, the main tasks are to qualitatively protect the junctions from blowing and water ingress and to ensure reliable fastening of the block. We propose to consider working with two types of roof windows in the context of their installation into a frame supporting structure made of lumber.
Installation of roof windows is carried out, as a rule, after the completion of the roofing work and installation of the rafter insulation. It should be noted right away that such an installation is quite acceptable, there are methods for its correct implementation and all the necessary materials for fastening and insulation. Having understood the principles of arranging the opening, you will be free to transfer work to any stage, up to the introduction of appropriate changes to the rafter system of the roof under construction.
If we are talking about an exploited house, it is necessary to remove the section of the inner lining of the attic. The cross-section of the opening should be between the supporting elements of the rafter system, therefore, first a small section is cut out, the rafters are groped by hand and then, taking into account the detected element, the markings are applied. The top of the opening should be 200–220 cm from the floor, the bottom – about 90–120 cm. The width of the window should be a multiple of the step of the rafter system. The interior trim is cut taking into account the dawn of the slopes of 25-30 mm on each side and the thickness of the window block box.
After removing the cladding, the details of the frame of the inner lathing are cut out. The vapor barrier unfolds along the center and temporarily turns to the sides, the insulation is removed from the section of the opening. If there is a rafter leg in the middle of the opening, it is cut flush with the upper and lower edges.
The formation of the opening in the pie is completed by the installation of two horizontal beams connecting the rafter legs. If the window fits completely between two adjacent rafters, they are fastened together with pieces of timber or boards of the same section. If one of the legs is cut out, the lintels should firmly support its remnants both at the bottom and at the top. The crossbars are fastened with steel corner brackets. Before final fixing, it is necessary to restore the insulating layer in the open sections of the roofing cake.
Please note that dimensions with tolerances for preparing the opening are indicated in the instructions for each individual window model..
The arrangement of the skylight allows the use of cheaper PVC frames for vertical glazing systems. An additional plus can be considered an increase in space inside the attic..
The aperture of the roof is formed by two rafter legs, between which it is allowed to cut one or two more, depending on the step and type of rafter system. The outer rafters of the opening are doubled in thickness and supported in the upper part by a rack of nominal cross-section. The upper edge of the support is trimmed to the angle of inclination of the roof, in addition, its bottom should be installed on the floor beam and rigidly connected with it.
Another pair of props is carried out parallel to the front of the opening, which forms a vertical pediment 30-50 cm before the Mauerlat or even directly on it. The front pillars are connected to the rafters with horizontal crossbars at the end, cutting them at an appropriate angle.
By reducing the length of the front struts, a slope of 9–11% can be achieved, which is optimal for installing a pitched roof over the dormer. Otherwise, the central transom and oblique rafters from it can be mounted, forming a gable canopy adjacent to the ramp to form two valleys. This option is more time consuming, but it allows you to put more insulation in the structure..
Difference between horizontal and sloped glazing
The decision to build a dormer window is made taking into account two factors: economic feasibility and the level of illumination of the attic. In the latter respect, skylights give half as much natural light as sloped windows, but this is leveled by the glazing of the main gables.
On the economic side: a regular PVC window of good quality REHAU costs 2-3 less than a roof window with a cover from a very mediocre manufacturer. On the other hand, to install a window into a roof slope, you will not need anything other than an installation kit, with the exception of a couple of beams.
The dormer window requires a fairly serious intervention in the rafter system. On average, 60 running meters are required for its arrangement. m of lumber, as well as additional insulation, waterproofing and roofing. Even so, vertical windows benefit from cost..
Another issue is heat-saving characteristics. With good insolation of the slope, the inclined window will, on average, heat the attic more than let heat out of it. If we are talking about an unlit north slope, here it is better to give preference to ordinary windows for the following reasons:
- they have a denser uniform porch;
- there is a free choice of double-glazed windows;
- the scheme of installation and sealing of junctions is more standard, there is no likelihood of leaks.
Window block insulation
But back to the installation: when the parts of the rafter system are removed and the frame of the opening is formed, it is the turn to make a gap into the street. Through it, markings are applied on the front side of the roof in order to cut out the covering and the lathing under it exactly along the borders of the opening. The waterproofing must be pre-cut with an overlap of 50–70 mm on each side to form the gates. Depending on the type of coating, it is very important to determine the installation order so as not to damage the under-roof waterproof membrane.
Usually, the fragments of the crate that fall into the opening are first removed. They are used to seal the cuts of the roof pie, then the waterproofing is tucked up and targeted at the fixed scraps. When everything superfluous has been removed from the opening, the roof covering is disassembled 20-30 cm in both directions from the opening and up to 50 cm above it.
Before continuing to work, all cavities in the cut of the pie must be filled with insulation. Further, a heat-insulating frame is inserted into the opening, brackets at the corners allow you to simply insert it into the opening. After aligning and fixing the frame, the first solid board of the crate is located above the opening, to which a drainage chute is screwed over the waterproofing, preventing condensate from flowing into the window block. In most window models, this gutter is then approached by a frame that surrounds the opening with a slight indent..
Securing the frame and finishing the abutments
Before installing the frame, four corner brackets are attached to it for fixing to the roofing system and the swing flap is unfastened. The window unit is simply exposed to the outside and then inserted into the opening over the insulating frame. After fixing the main adjustable brackets at the corners, it is possible to add additional fastening points – usually on the sides and at the points of abutment of the rafter legs to the block.
The waterproofing tape supplied with the roof window is aimed around the entire perimeter of the frame and applied to the crate with waterproofing of the roof. Its upper part is wound under the waterproofing up to the point of attachment of the water-cutting gutter, from the other three sides the tape is admitted to the window block from above, after which all edges are glued with aluminum tape.
At the final stage, the skylight is assembled. It is represented by four adjustable (sliding) slats that fit tightly to the outside of the window unit. The cover should cover the roof covering in the lower part of the opening, on the other three sides the roof is poured over it.
After sealing the roof junctions, the interior decoration should be done. The frame of skylights usually has a groove for inserting a slope sheet. Fastening is done to the body of the rafter leg or counter-lattice on it, if you need to provide a steeper dawn. The entire space between the slope and the roof system should be filled with the same insulation that was used in the cake.