The basic elements of trellises and pergolas are poles. These columns carry not only vertical loads, but also the forces acting in the horizontal direction. Climbing plants overgrowing pergolas or trellises with a dense weave of shoots create a very large area over time, which loads the poles significantly during gusts of wind. This load may cause deformation or damage to the structure. The poles may also be overloaded in winter, if a large amount of wet snow has accumulated on the pergola, ice etc.. For the reasons discussed above, pergolas and trellises should be characterized by adequate Stiffness and should be properly embedded in the ground..
Trellis and pergola poles are made of various materials, however, the most common are poles, brick from various stones, concrete, metal and wooden.
Wall posts are made of various types of natural or artificial stones. Natural stones should be treated in this way, that each of them has at least two support planes (parallel to each other) and at least one plane perpendicular thereto. Due to the ease of processing, the most frequently used natural stones are sandstones and dolomites. Stones for the construction of poles can have natural fracture surfaces or can be cut into blocks or slabs of various sizes. The stones may be of the same or different sizes, in the latter case, they must be properly selected in order to properly bind the entire system and ensure the appropriate appearance of the surface (proportions, size).
Cement mortar is used as a binder to connect the stones in the pole. Depending on the design intentions, the mortar used can be lightened or darkened by adding appropriate dyes to emphasize the joint line.. For the same reasons, different depths of joints are used in relation to the column surface: flat joints, concave, and sometimes (if the edges of the stones are not worked well) also convex welds.
Of the artificial stones used in the construction of poles, first of all, clinker brick and sand-lime brick should be mentioned. The use of ordinary brick is not recommended due to its lower strength and high water absorption. Should be added, that regular brick posts require plastering, which contributes to the increase of the construction cost. Made of clinker bricks, or sand-lime, poles of sufficient strength can be built, if bricks are stacked crosswise in pairs. Columns made of clinker bricks, depending on the way they are arranged, may have a wall width 22 or 34 cm. The columns of sand-lime bricks can be wall-wide 25, 33 or 38 cm.
A cement mortar is used to connect the bricks, which can be colored. The big advantage of poles, as well as other elements of garden architecture made of clinker bricks, the color is nice and the surface is kept clean.