In this opportunity we will present a synthesis of the application of sheets of fiber cement on external walls and facades of buildings. In general the working procedure for finishing of walls (external or internal) with fiber cement is very similar to the working system of the Dry-Wall, but keeping the difference that fiber cement sheets are heavier and, when used as an element external, a series of premises must be honored
that guarantee its correct use, an excellent finish and therefore a long durability.
As a first consideration it is necessary to define two types of exterior walls according to their structural requirements:
- External walls embedded: those walls confined between main structural components such as beams, braces and / or slabs; in which case its effort requirement is given by the bending and lateral loads, the wind and the possibility of seismic activity and its development is usually confined from floor to ceiling.
- Supporting external walls: subjected to axial bending stresses and other types of lateral loads, they require a detailed calculation and their development can include heights of several floors.
The field of action for the application of fiber cement as an element of exterior walls or facades comprises any of the above types, considering that in the case of load-bearing walls the structural element must solve by itself the requirements of building effort, this structural element It must be complemented with the support elements for the fiber cement sheets in accordance with the general recommendations of the installation.
The fiber cement system for application as exterior walls or facades comprises the supporting structural element, the sheets of fiber cement, the anchors, the fixings and the solution of the joints.
They are profiles designed to support the sheets of fiber cement, and is made up of the following types:
- Meeting profile (PE): is a type “C” profile of galvanized sheet, size 20 to 22, with a core section between 92 to 150 mm, wing between 50 and 100 mm, and a 12 mm fold. The purpose of this profile is to function as sufficient support at the meeting point between two sheets and to avoid the appearance of cracks between the joints of the sheets.
- Anchoring profile (PA): it is a “U” type profile of galvanized sheet from 20 to 22 with a core section between 92 to 150 mm and 32 mm wing. and it is used as a mooring profile of the vertical profiles at the upper and lower ends.
- Vertical profile (PV): it is a profile “C” type galvanized sheet gauge 20 with a section of core between 92 and 150 mm, 32 mm wing and 12 mm fold, whose function is to configure the screening of longitudinal support of sheets ; these profiles are arranged with a separation distance between 610 mm and 406 mm anchored at their upper and lower ends inside the PA. The use of wood instead of the galvanized zero profile is a valid option, considering the use of structural type wood duly treated to support the humidity, pests and weather conditions.
Fiber cement sheets
- Exposed joints: In the case of contemplating a panel design, where it is considered as a design element that the joints are visible, the recommended sheet type is PLYSTONE of 11 mm and 14 mm of dimensions 1,219 mm x 2,438 mm. It should be considered that fiber cement sheets can be coated with any other type of finish, such as: paint, ceramic, stone, etc.
- Joints not exposed: In the case of contemplating that the final finish is without exposure of the joints, the recommended sheet is PLYROCK 11 and 14 mm of dimensions 1,219 mm x 2,438 mm. This type of sheet allows the joints between the sheets to be hidden by the use of a mesh tape and the application of special mastic on the joint area.
- Fixation and assembly of the structure: It is recommended the use of galvanized steel screws # 8 x ½ “or ¾” flat head anti-slip tread high low fine tip self-drilling, for structures up to 0.8 m thick and hardware of galvanized steel # 8 x ½ “or ¾” self-drilling “S” type thread for structures up to 1.4 mm thick.
- Fixing of the sheets: It is recommended to use the galvanized screw type “Tek” self-sealing # 8 x 1 “1/4” thread S12 for fixing the sheets of 11 m and 14 mm to galvanized steel structures between 0.8 and 1.4 mm. It is essential to remember that the fixation of the screws in the corners must be placed in a 90º pattern, since otherwise the sheet is cracked as a consequence of the arrangement of the fiber cement components oriented at 45º. The total number of screws holding a PLYSTONE or PLYROCK type sheet with vertical supports (PV) arranged at 610 mm each is 58 screws, while the total fixing screws for a type sheet with PV arranged at each 406 mm is of 66 screws.
For the fixation of the PA, distinctive anchors can be used depending on the type of structure between which the profile is confined, in this sense the mechanical anchors, expansion or by means of the combination of mechanical anchorage + chemical epoxies, are useful; In any case, the fundamental premise is to specify that the anchorage is adequate and offers protection against environmental corrosive elements.
Seals and additives
For the finishing of the walls or facades, the treatment of the joints between sheets, the encounters between sheets and the stops against the structure is required. The most advisable is the use of monocomponent elastic seals based on high elongation polyurethane. This type of product allows to hide the joints tolerating the natural structural movements due to the expansion and compression of materials. As an exterior finishing application, the SIDING system is also highlighted in any of its two modes: tongue and groove or overlap, which offers an elegant and professional exterior finish to buildings of all types. However, this application and its features will be developed in greater detail in the next edition.
In H. Welle, S.A. We advise you on the type of fiber cement material most suitable for your construction project, ensuring the availability of all the components of the construction system with fiber cement and the broadest stock in the country at your disposal.