One of the most traditional roof designs is the envelope roof. How it is arranged, what are the specifics of its installation and operation - later in the article.
General terms:
- Ridge - the place of the vertical junction of the roof slopes
- Hip - a triangular slope located above the end walls
- Rafter - a supporting structure, more often - a triangular shape, taking on the load from the weight of the roofing material, snow and wind
- Rafter leg - an inclined beam on which the roofing material directly rests
- Rafter beam - a strapping that runs along the top of the walls, on which the rafters rest
According to the architectural classification, the “envelope” is nothing more than a hipped or hipped roof. When viewed from above, it really resembles this item.
The peculiarity of this form of roofing is that it replaces with its two slopes the traditional elements of a house with a gable roof - gables, made as a narrowing of the end walls upwards. It has its advantages, it also has disadvantages.
It all depends on the conditions in which the new coating of the house will have to work.
Hip roof device
Like any pitched (with a slope of more than 10%) roof, the hip is performed using a truss system. However, due to the special location of the slopes, some of its sections have features.
All roofs with rafters are divided into two types:
- With hanging rafters that do not have intermediate supports in the middle, the entire load falls only on the external load-bearing walls
- With layered rafters - they have one or more intermediate supports on load-bearing walls located inside the building, or on floor slabs
If for gable roofs the entire truss system is made the same along the entire length of the building, then for hip roofs, a rather complicated junction is created at the ends of the walls - after all, in fact, two perpendicular supporting structures converge here.
Therefore, here, as a rule, layered rafters are used - and in the place where the hip adjoins the ridge, a support is just installed. The supporting structures of the slopes converging at this point just rest on it.
As a result, the rafters from the hip and side slope converge at an angle on the rib.
Important information!
- Corner rafters always always have a smaller slope than the rest
- The short rafters of the slopes are not attached to the roof ridge, but to the corner rafters
- Intermediate rafters - those that rely on the ridge and rafter bars
A special case of a hipped roof is a hip roof - it is installed on buildings that are square in plan. Here, all the slopes are hips, that is, they have the shape of identical triangles.
It is logical that in the center, where the rafters from all the slopes of such a roof converge, the support is almost always installed (with a layered system).
In the tent do-it-yourself roofing the calculation of the convergence point of the rafters of the four hips is of particular importance, since it is quite easy to make a mistake. For these cases, there are various auxiliary tables:
Roof slope Coefficient for Corner rafter coefficient
intermediate rafter
3:12 1,031 1,016
4:12 1,054 1,027
5:12 1,083 1,043
6:12 1,118 1,061
7:12 1,158 1.082
8:12 1,202 1,106
9:12 1,25 1,131
10:12 1,302 1,161
11:12 1,357 1,192
12:12 1,414 1,225
According to the table, you need to take the desired angle of the roof, and multiply the distance between the rafter (strapping) and the ridge beam. The result is the desired length of the rafter leg.
Calculate roof pitch laying in degrees and percentages, as well as the following table will help you choose the right roofing material:
Benefits of the hip
On the "protractor" scale - in degrees
It is clear that the first, and one of the main, advantages of such a design as hip standard roof - saving wall materials in the upper part of the end walls of the building. Here it is much easier to install skylights. Also, with proper design, all walls of the house will be evenly protected from precipitation.
Such a roof, among other things, equally resists the wind from all sides. Finally, in most cases, the hip roof is just very aesthetic.
In the southern regions they love these, because climatic conditions allow them to be installed and equipped inside with useful premises.
There are also disadvantages
The ideal version of building structures does not exist. You just need to choose the right one.
What to consider when installing a hip roof:
- With the same building material as a gable roof, due to the larger area, it will proportionally increase its weight
- Since the rafters are supported around the entire perimeter of the building, all walls automatically become load-bearing.
- The truss system has a much more complex design and does not forgive mistakes.
- Attic equipment in cold areas will require a significant amount of insulation
If the roof of the envelope, after all the pros and cons have been weighed, has inclined the owner of the building in its favor, and difficulties do not frighten - its elegant appearance will please the eye. And it will serve, if all the calculations were correct and the roofing material was successfully selected, for at least 50 years.
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