What affects the height of the ridge?
Anyone unfamiliar with the features of the layout and calculation of a gable roof can intuitively guess that the height of the ridge cannot be selected. This is indeed the case.
The height at which the line of joining of the two slopes is located determines two main factors that determine the viability and price of the roof rafter frame:
- The length of the rafters. The higher the ridge is raised, the longer the rafter beams;
- With an increase in the height of the ridge, the cost of beams, spacers, and struts increases;
- The higher the ridge, the greater the consumption of roofing, film steam, and waterproofing, insulation, lining material;
- The windage of the building increases, if the height of the ridge exceeds the limit value determined by the calculation, a situation is possible when the box of the building is not able to hold the roof.
- In calculating the parameters of the roof, the factor of influence of atmospheric phenomena is taken as one of the most important. An equally important characteristic depends on the height of the ridge – the angle of inclination of the roof slopes, the higher the ridge, the greater the slope. Using the slope intercept form calculator, you can easily get the solution for the slope of the roof.
For your information! A gust of wind of medium intensity creates a dynamic pressure normal to the surface of the roofing cake. Reaching 20 kg per square meter.
For note, get the estimation of the weather prediction in the form of percentage using the percent error calculator.
An increase in the angle of inclination by 5 ° will mean that the height of the ridge and the length of the roof slope will increase by almost 10%, respectively, for 10 ° the increase will be almost 30%.
It would seem that rainwater drainage has improved and the volume of heat-insulating under-roof space has increased. But at the same time, the wind pressure increased by 30%.
The calculation shows that the pressure of the high-speed airflow on the plane of an ordinary gable roof with a size of 8×8 m is more than 1200 kg. Which in itself is a lot, given the strength of the rafter beams. In these conditions, an additional 400 kg can be fatal for the roof Mauerlat.
Builders don’t like tall skates. This usually means that the roof beams will have to be purchased at an inflated price. It turns out that the higher the ridge height, the more expensive the material for a gable roof is.
For a bar, more than 6 m long, the price per meter grows almost in arithmetic progression. In addition, the rafter beams have to be spliced, and due to the change in proportions, they become excessively flexible. To prevent too much deflection, check the deformation of each beam and be sure to use braces.
The height of the ridge cannot be increased arbitrarily also for reasons of the stability of the roofing. Before calculating the height of the gable roof ridge, you need to decide on the type of roofing.
Most manufacturers give recommendations on the optimal angle of inclination of a gable roof for a particular type of roofing material.
For example, flexible shingles cannot be laid on a roof slope with a slope of less than 16 ° and more than 40 °, and ondulin and metal tiles are not used on slopes with an angle of inclination of 60-65 °.
Positive aspects of increasing the height of the skate
There are only three main advantages with a plus sign that arise with an increase in the height of the ridge:
- Reducing the pressure of the snow cover;
- Increase in the usable space of the attic due to higher ceilings;
- Improving ventilation of the under-roof space, reducing the risk of rainwater flowing under the roofing cake. Reducing the cost of insulation due to a larger air cushion.
A roof with a high ridge is ideal for dense urban areas. Where there is a lot of precipitation in the form of snow, rain, and fog. Such a roof is often not even equipped with full-fledged thermal insulation. Since the air pocket in the attic reduces heat loss 3-4 times more efficiently.
But for gable roofs with a high ridge, a special design of gables will be required. A more effective solution would be to replace the gable roof with a half-hip Danish scheme.
Before making a choice about which angle is most suitable for a gable roof. It will be appropriate to compare the advantages and disadvantages that an increase in ridge height entails.
For example, how important it is for the owners to have large attic space. A simple geometric calculation shows that trying to equip a living space on the second floor of a building with a conventional gable roof is usually ineffective. In this case, less than half of the workspace is used.
For your information! If the height of the walls of the attic room of a gable roof exceeds 120 cm from the level of the ceiling. The building inspection can qualify it as a second floor and prohibit construction or refuse to register the building.
At the same time, the cost of erecting a roof truss system due to the additional amount of lumber and insulation will increase by more than 70%. It will be necessary to re-calculate the estimate. Calculate the cost of workers’ services, and most importantly. Recalculate the strength of the rafter beams for the new ridge height.
As a result, it turns out that a gable roof with a ridge height of more than two heights of the walls of the building. It is advantageous primarily for summer cottages. When the attic is not insulated and is used only as a utility room. But even in this case, the height of the ridge for a gable roof must be calculated according to science.