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Instruction manual for the construction of exterior walls

The following manual is designed to provide a brief guide in regards to the installation of the approved and recommended exterior sidings Fiberock® Aqua-Tough, Durock®, Securock® y Densglass.

As a brief history, in the US there are many types of exterior siding systems. Most of them are more complicated than those used in Costa Rica. The most similar system is known as DEFS (Direct- Applied Exterior Finish System. Following are the minimum specifications for this system:

  1. Tracks and Studs placed every 40.5cm, both 20GA gauge.
  2. Water seal adhered with the appropriate water repelling tape.
  3. DEFS, Durock® approved siding with galvanized screws every 20cm.
  4. Installation of gutters.
  5. Drywall polymer mortar application for the joints.
  6. Alkaline and UV resistant fiberglass mesh for exteriors.
  7. Application of a continuous layer of drywall mortar of the same specifications on the entire exterior surface.
  8. Application of wire mesh which prevents cracking and helps add support from high winds and seismic tremors.
  9. Application of sealant and finished with paint or other method of your choice.

Another exterior siding system is the Exterior Insulated Finish System, also known as EIFS. Following are the minimum specifications for this system:

  1. Tracks and Studs placed every 61cm, both 20GA gauge.
  2. Water seal adhered with the appropriate water repelling tape.
  3. EIFS, Fiberock®, Securock® o Densglass approved siding with galvanized screws.
  4. Installation of gutters.
  5. Application of an expanded polyethylene thermo acoustic insulation, ranging from 1” to 6”.
  6. Application of a continuous layer of drywall mortar of the same specifications on the entire exterior surface.
  7. Application of wire mesh which prevents cracking and helps add support from high winds and seismic tremors.
  8. Application of sealant and finished with paint or other method of your choice.


Durock is manufactured from Portland cement wrapped with two layers of alkaline resistant fiberglass for reinforcement. Durock is the only substrate approved for DEFS applications. If desired, the EISS system can also be used.

Fiberock is derived from plaster, which is pressed and treated with silicone in an autoclave as to make impermeable, also rendering paper or carton lining unnecessary. The product has the same water resistance throughout. It does not separate, it is anti fungal, it does not contain fiberglass and it is produced from 95% recycled materials. It is categorized for heavy duty use. In applications where exposure is limited to ambient moisture and not direct contact with water, installation can be performed with mortar for interiors. Due to Fiberocks weight, a a minimum of 20 gauge is recommended. Fiberock is recommended for EIFS exterior applications.

Securock and Densglass are both plaster laminates pressed between two layers of permeable paper and fiberglass. The edges must be sealed no matter whether they come straight from the factory or cuts made on site. They are treated with anti fungal and mildew resistant properties. Securock and Densglass are recommended for EIFS. The girth of the steel to be used with this system is to be determined by the foreman in charge of the project, but it is ideal that it be selected by the structural engineer in charge.

For more details and or consultations, please feel free to contact us.