In this installment of the "Do it yourself frame house" series of articles, we’ll talk about roof construction guidelines, when to do it, how to measure rafter spacing accurately, what kind of material to use for the roof, and how to insulate the roof.
Since the roof structure is known to be heavy, it must rest on the walls. In this instance, the walls are the vertical frame posts that are bevel-secured, joined by an upper trim beam, and covered in OSB on both sides. Slab cladding extends to the center of the upper trim beam. Our frame turned out to be sturdy and able to bear the weight of our roofing system. External and internal wall cladding finishing should be done after the roof is installed. When the walls are complete, the overhang trim is put in place.
Eaves and pediment overhang.
In the event that the roof structure includes gables, OSB sheets are typically installed and sheathed prior to roof assembly. Since the top line of the gable depends on the chosen slope, the roof slope must be established before the gable is installed. Once the outer trusses are installed and braced in place, numerous experts erect the roofs and gable at the same time.
If the project calls for an attic floor, low walls must also be built and covered after the roof is installed, in addition to the gables on the eaves side.
A beam of upper trim is installed on all four of the attic floor’s walls, including the spot where the pediment is supposed to be built. The top frame beam’s purpose is to support the rafters and should have the same cross-section as the top frame beam of the first floor.
It is obvious that you must choose the roof’s configuration before building it. Recall that our home is 6 by 8 meters in size.
The cross-section of the frame elements—the 180×130 mm floor beams with a 600 mm step and the 100×150 mm upper strapping beam—was what we used.
Prior to roof installation, we ascertain the number of slopes, roof slope angle, roofing material, and, lastly, the appropriate choice of rafter, sheathing, and counter-sheathing cross-sections.
Number of slopes, the more complex the roof, the more beautiful it looks, but it turns out to be more expensive, more difficult to operate. As a rule, customers choose a gable roof citing costs and beauty. If you make one slope, the roof will be simple and boring, a four-pitched (hip or hipped) will cost more. We will stop at a gable roof, such a roof is suitable for a cold attic and attic floor (while the walls of the attic floor must be at least 1500 mm, and the slope is no more than 45 degrees. A gable roof has one ridge and there are no valleys in its design. This is very good, because the valley and ridge are the most problematic places in the roof, the most difficult to install the roof structure.
Selecting roofing materials for a frame home’s roof.
The roofing material determines the acceptable slope of the slopes. Since every roofing material has a recommended slope range that must be followed in order for the material to be installed safely. In other words, it won’t slide and won’t hold onto snow for longer than it should. You can lay on a slope that is higher or lower than what is suggested, but you will need to make some adjustments to the roof structure. Some of these adjustments include adding more waterproofing, laying the sheathing more frequently or replacing it with a continuous deck, fastening the roofing material more frequently, etc. P. Allowed inclinations for the most widely used roofing materials:
- cement-sand and ceramic tiles – 25-60°;
- polymer sand tiles – 20-60°, a smaller angle is allowed when the sheathing is reinforced;
- bitumen shingles – from 12° (maximum slope is not limited);
- metal tiles – from 20°, a slope of 15° is allowed, provided the joints of the metal tiles are sealed;
- corrugated sheeting – from 10°;
- asbestos-cement sheets (slate) – 12-60°;
- bitumen corrugated sheet (aka Euro slate, bitumen slate, ondulin) – from 15°, a slope of 10° is allowed when reinforcing the sheathing and from 5° when replacing the sheathing with a solid flooring.
We’ll use bitumen slate, which is the most common roofing material in low-cost construction, for our example. Its affordability, attractiveness, and lightweight nature are critical components of its economical construction. The only issue is that over several years, the material from various manufacturers fades uniformly. However, when installed properly, there were no complaints regarding this material—aside from the color (burnout).
Slope inclines.
A roof is classified as pitched if its slope is greater than 5 degrees, and flat if its slope is less than 5 degrees. Pitch roofs that have a slope of less than 28 degrees are classified as loaded, and the components that support them must adhere to stricter specifications. Because of the increased snow load (snow does not slide off the roof well; nearly all of it remains on the roofing), rafters with a slope of less than 28 degrees must be stronger. Additionally, wind loads rise at slopes higher than 50°.
For loads, a slope between 35 and 45 degrees is ideal. In terms of appearance, this slope also appears to be the most favorable. Neither too flat nor too sharp is the roof. At a 45° slope, we’ll stop.
So, on a house 6×8 m we will have a gable roof with a slope of 45 degrees, covered with bitumen slate. We will also assume that under the roof we will have a residential heated attic floor. The walls of the attic floor are raised by 1.1-1.6 m. This height depends on the comfort requirements. But 1.1 m is the minimum so that you can conveniently use the under-roof space. With such a height of the walls under the slope in the lowest place, you can, for example, place a sleeping place or a wardrobe. If there is a cold attic, then the roof structure will be the same, only it will not be insulated (the floor of the attic will be insulated) then the walls do not need to be raised by 1.1-1.6 m.
Frame house roof diagram.
Let us decide on the diagram for the roofing structure. Do you require more purlins, crossbars, struts, tightening, etc.? Following the scheme’s final determination, the sections of each element can be chosen, and the quantity of lumber can be determined.
A roof in the shape of the letter "A" works well for a 6 by 8 m home. Rafts and a crossbar make up this structure (it is also referred to as a tie, crossbar, lintel, bow, etc.).
Roof structure shaped like an "A".
Section of rafters of a frame house.
Our roof will be insulated because our option has a residential attic. In order to ensure that the insulation fits between the rafters in terms of height, the rafters’ cross-section must be chosen carefully. Calculations typically indicate that the roof needs between 100 and 150 mm of insulation (less frequently, more than 150 mm). This insulation should therefore fit between the rafters in terms of height.
The rafters’ cross-section can even be 100×50 mm if computations indicate that up to 100 mm of insulation is needed. However, a calculation of this small section of the rafters is required for each unique situation (e.g., whether they can bear the snow load in a given area, what their pitch should be, etc.). This computation is performed by us. Without doing any calculations, we advise being a little cautious and using rafters with a 150×50 mm cross-section even with an insulation thickness of up to 100 mm.
The rafters measure 150×50 to 150×70 mm if the insulation is between 100 and 150 mm. Increasing the smaller side (between 50 and 70 mm) is pointless because a square cannot support as much weight as a rectangle. The cross-sections of all channels and I-beams serve as an illustration of this.
The rafters are 200×70 mm if the insulation is more than 150 mm.
We’ll use the 150×50 mm cross-section of the rafters as our example.
Length of frame house rafters.
Choice regarding the lengths of the rafter. In practice, we employ it. It is especially appropriate if you are unsure about the future roof’s slope because you can’t be certain how a certain angle will appear in practice.
Take two long slats, about six meters long, and use a nail to knock one side of each down to form the letter "L." We’ll use this as our trial truss. Without lifting it into position for the future roof just yet, we fix it on the ground.
Next, we make a test crossbar, which is a long strip that we will measure and attach to the test rafters at the necessary level.
After hoisting them up onto the roof, we place our letter "L" on the upper trim beam. We now attempt to adjust the angle, which also affects the rafters’ length. deciding on the ideal slope angle. The length of the rafters as a result can then be measured. With the rafters’ overhang "behind" the wall taken into consideration, the length should be between 30 and 55 cm. A sample of rafters is provided.
Remark: The overhang shields the windows and house walls from precipitation. The overhang should be at least 50 cm in accordance with the standards if an organized drainage system from the roof (a drainage system in the form of gutters and pipes) is not intended to be installed initially or will not be installed at all. Even with a drainage system, creating a 50 cm overhang is not a bad idea; it looks great and will better shield the external walls.
When choosing the length of the rafters in this way, you need to take into account that after installation they will “sit” 5 cm lower on the Mauerlat. Since the rafters are necessarily cut into the Mauerlat for greater stability of the connection. In each rafter, at the point where it rests on the mauerlat, a triangle is cut out with approximate dimensions of 5×5 – 5×6 cm with a rafter cross-section of 150×50 cm. If your cross-section is different, then the side of such a triangle will be approximately equal to 1/3 of the height of the rafter. This placement of the rafters does not in any way affect the selection of the roof slope angle and the length of the rafters. Just visually after installation the rafters will be lower by about 5 cm. Plus, when trying on rafters, you need to mark on the underside of the rafter the place where the rafter rests on the mauerlat and draw a vertical line upward from it. This will be one of the sides of our triangle. The second can be completed on the ground, at an angle of 90 degrees to the first.
Supporting structure on the mauerlat for the rafters.
Pitch of rafter in frame house.
The pitch of the rafters depends on their cross-section, as well as on the size and slope of the slopes. As you understand, there are a lot of options for different combinations of these parameters; it is not possible to register all possible rafter pitch options for their different sections, slopes and slope sizes. In our example, the rafters have a cross-section of 150×50 mm, the house is 6×8 m, the slope is 45 degrees. And for this option, the suitable rafter pitch is 70-80 cm. If you have approximately the same parameters, then a step of 70-80 cm will also suit you. If the parameters are different, then ask and we will select a step specifically for your case.
Note: Since the width of the insulation roll is typically precisely 60 cm, it is occasionally advised for insulated roofs to have rafter spacing equal to 60 cm. This will prevent the insulation from needing to be cut. We advise against modifying the insulation because doing so will result in more rafters because you will be reducing their pitch, which could lead to, say, 18 rafters instead of 12. The weight of the roof structure will rise as a result. extra weight on the foundation and walls. Cutting the insulation to the necessary rafter spacing is not too difficult because it is easy to cut.
We calculated the length, pitch, and cross-section of the rafters as well as the dimensions of the support cutout (triangle) that will support the rafters on the mauerlat. We also worked out how to get a rafter sample ready.
Currently, we apply the rafter sample—which is already on the ground—to the bars that have been set aside for the remaining rafters, give it a try, mark it, and cut it to the necessary length. Simultaneously, we promptly arrange the necessary quantity of rafters for the complete roof.
Note: There must be a single sample, and the measurements for each rafter after that must be based on that one and only sample. If you measure the second rafter based on the first, the third rafter based on the second, the fourth rafter based on the third, and so on, then the error will mount up until it reaches an unacceptable size. For instance, with ten rafters, the error will already be two centimeters even if each rafter is only 2 mm longer or shorter than the preceding one. T. e. there will be a 2 cm difference in the length of the first and last rafters.
Rigel.
The crossbar should be placed as low as possible, but not lower than the planned ceiling of the first floor. The lower the crossbar is located, the better it accepts the thrust, and if you fix the crossbar high, it will not perform its function. Let"s select the minimum height of the crossbar for our example. 2.1 m only the height of the entrance doors (if the crossbar is lower, the doors will no longer fit). Plus about 10-20 cm (0.1 – 0.2 m) above the door and another about 5 cm (0.05 m) for the ceiling finishing material. Total we get 2.25-2.35 m. This is the minimum distance from Rigel to the top of the final floor at the height of the doors 2.1 m. If you find doors 2.0 m high, then the crossbar can be placed even lower, at an altitude of 2.15-2.25 m from the top of the final floor. It is also important to remember that the smaller the cubature of air in the attic, the less heat it will be necessary to spend it on heating. This can also be attributed to the pluses of low selection of the crossbar.
Naturally, the standards state that residential buildings’ ceilings must be at least 2.5 meters high. However, 2.15-2.35 m is obviously quite appropriate for bedrooms, assuming that growth permits.
Rigel is taken using a 50 x 150 mm section. i.e. the area where the rafters are. As a result, there is no confusion when placing an order for a tree at a sawmill, and any leftover rafter residue can be turned into a crossbar.
The rafters’ step and Rigel’s step are identical. For us, it was 70–80 cm.
Make contact.
It offers a space for upper ventilation in the roof. The roof needs two ventilation gaps, each 2-4 cm high, and waterproofing whether or not it is insulated.
- lower ventilation gap – under the waterproofing (to ventilate condensation that can accumulate on the inner surface of the waterproofing when the humidity in the room increases).
- upper ventilation gap – above the waterproofing (to ventilate condensation that can accumulate on the inner surface of the roofing material).
The typical functioning conditions of wooden roofing components are also due to these two ventilation gaps. Additionally, there is a much higher chance that wooden components will mold, bloom, or develop a layer of fungus if there is even one missing gap.
Counter-battens provide the upper ventilation gap. The rafters are where it is fastened. Section 20×50 mm, with 20 being the height. Since the counter-lattice is fastened along the rafters (on each rafter), the pitch is the same as the pitch of the rafters (70–80 cm in our example).
Sheathing and counterlattice
Lathing.
The roofing material affects the sheathing’s cross-section and pitch. It is attached to the roofing material, which is bitumen slate in our case. Additionally, it stabilizes roof trusses. Bitumen slate sheathing has a 40 x 50 mm cross-section with a 35 cm pitch.
The sheathing is laid long enough to provide an overhang (overhang) of 20 to 50 centimeters beyond the outer rafter. The overhang of the sheathing and the rafters, whose edges extend past the outer walls, are often made of the same material. Thus, for instance, if the rafters’ overhang is 50 cm, the sheathing’s overhang is frequently 50 cm as well. It is more practical to slightly increase the sheathing’s overhang when repairing it, then trim off any excess. Unedged boards can also be used as lathing to save costs.
You can order timber once you’ve determined the fundamental specifications for each roof element. When placing an order, keep in mind that ordering lumber in standard lengths—even longer than necessary—is always more profitable and that there is always a place to use the leftovers when building a frame house.
You can buy dried or undried wood. We advise taking it wet, but they also suggest undried. Since dry wood is so costly, it is typically dried for furniture, lining, etc. The cost of dry timber is now per square meter rather than per cubic meter. Ordinary non-dried wood from a sawmill works well for the roof. The most important factor is that the tree is unaffected by fungus; these trees have a gray appearance. Furthermore, in order to prevent a future infestation of the bark beetle, you must remove all of the tree’s bark.
A combination antiseptic treatment is required for all lumber. To prevent the wood from moving, this can be completed prior to assembly: soak, let dry for a few hours, and then install right away. Alternately, install it right away and use fiberglass to impregnate it onto the roof. While this method is obviously simpler, in this instance the internal planes of the wooden elements at the points where they are connected to each other will remain untreated (it will simply not be possible to reach there with anything).
A list of the basic tools required for roof construction. The following tools are needed: a 50 m nylon thread, a screwdriver or drill, a hammer drill, a grinder, an electric plane, a 90 degree square, a tape measure, a brush, and a laser or water level.
Installation of a frame house’s roof.
There are numerous methods for fastening the roof’s main components. This comprises a notch, a connection made with steel or wood plates, a nail connection, etc. These days, options abound. Using nails to make a connection is the most economical choice.
Let’s now examine a low-cost alternative for joining the major roof components in the main units. Naturally, keep in mind that there are other options. Every node has an alternate that you can always choose from. More of an example would be this.
Rafter connections in the ridge.
As seen in the figure below, it is convenient to use the half-foot method to join the rafters together in the ridge. cut with a chainsaw with ease. Three or four 100–150 mm long nails are used to connect this unit if the rafters have a 150×50 mm cross-section. On the other side, bend the nails.
Attaching rafters in the ridge with half-foot connections.
Attaching the beams to the mauerlat.
Under the mauerlat, also known as the upper frame beam, the rafters are pre-cut. 200 mm nails nailed in from above at the thinnest point of the rafter. Each side has one angled nail, for a total of two nails. The nail strikes the beam after passing through the rafter.
Joining the rafters with the crossbar.
On one side, rafters measuring 50 by 150 mm are fastened directly, without the need for spacers, to a crossbar with a cross section of 50 by 150 mm using 150 mm nails. From the back, bend the nail.
Inverse lattice.
Black wood screws measuring 35 mm in length are used to fasten 20×50 mm in close proximity to the rafters, with intervals of roughly 50 cm.
Lathing.
"We offer step-by-step instructions and crucial advice in our in-depth guide to DIY roof installation for frame homes for homeowners who want to take on this demanding but worthwhile project themselves. Our article aims to equip readers with the knowledge and confidence to successfully complete their roof installation by going over everything from initial planning and safety considerations to the step-by-step process of installing roofing materials. We stress the significance of meticulous preparation and adherence to local building codes. Whether you’re starting from scratch or remodeling an old roof, our guide gives you the knowledge you need to build a long-lasting, expertly finished roof.
At the intersections, 40×50 mm is fastened to the rafters using a single 60 mm self-tapping screw.
