Costa Rica Construction Problems & Solutions

After reading several postings and receiving various photos from disgruntled owners over the past months detailing problems with buildings in Costa Rica where moisture has entered the interiors through cracks in the exterior concrete coating, I have consulted and met with manufacturers and specialized tradesmen in the USA and Costa Rica and submit the following information to troubleshoot wall cavity water infiltration and to suggest permanent solutions utilizing the least invasive materials and installation methods.

In several of the photos sent to me, the interior damage caused by water intrusion into the wall cavity is very obvious and this will require extensive interior demolition, remodeling and mold remediation. Once the exterior water infiltration has been contained, these buildings need to be inspected by a knowledgeable professional who has extensive experience with modern construction materials and current remodeling procedures in order to restore the dwellings to their previous new condition.

Additionally, a mold remediation specialist needs to be brought in to inspect the interiors of the dwellings and specify the methods to contain and remove the existing mold which causes long term respiratory and skin ailments.

From the photos sent to me, it is clear that the current repairs being completed are temporary. Applying caulk and painting materials to extensive cracks on exterior concrete coatings, applied to pre-fabricated sheathing materials is an inadequate bandage for a terminal problem.

It is the responsibility of the professional architect or engineer to identify moisture related risks associated with any particular building design. Wall construction design must effectively manage moisture, considering both the interior and exterior environments of the building, particularly in buildings here in Costa Rica that have a high risk of wind driven rain penetration.

In addition, the professional with design responsibility needs to account for all wall openings, penetrations, junctions, connections, window sills, heads and jambs that require appropriate flashings for waterproofing. Flashing materials should be lapped in such a way that water tracks down to the exterior on the face of the buildings weather barrier surface.

Allowed to penetrate behind siding, wind-driven rain and moisture can saturate walls, creating a breeding ground for mold, mildew and wood rot. Weather barriers help combat water, moisture and air infiltration that are any structure’s worst enemies. A weather barrier may not be required by the local building code however the design professional should recognize the importance of an inexpensive weather barrier for the future energy efficiency of the owner’s project.

The other materials, components and installation methods used to manage moisture in external walls should be installed in harmony with the final exterior coating and all structural building materials should be kept dry and under cover while in storage and during the installation in order to avoid moisture accumulation in the wall cavity. Furthermore, the vertical fixing of the weather barrier and exterior sheathing panels should be aligned to allow moisture to escape out of the bottom of the exterior wall cavity in the event of excessive precipitation like we are experiencing now here in CR. From the appearance of the interior water infiltration in the photos, it is doubtful that a weather barrier was installed but this can only be determined by a detailed inspection performed by a neutral third party professional who understands modern structural construction, sheathing and exterior coating materials and installation procedures.

A weather barrier, like Dupont Tyvek, would be the preferred product installed on the exterior of the building structure before the exterior sheathing laminates and the concrete coating were applied. That way in the event the exterior concrete coating cracked, no moisture would have been allowed to enter the wall cavity and the interior of the dwellings. Weather barriers of this type are typically rolled membrane products for vertical building envelope protection that will maintain air/moisture resistance while maintaining moisture-vapor permeability.

The following building materials and installation methods could be used to permanently correct water infiltration problems.

1. Once the rain has subsided and the exterior of the buildings have had a chance to dry out, install a weather barrier product over the existing exterior surfaces. If this procedure is attempted before the walls have been dried, the existing moisture will be trapped inside the wall cavity, causing extensive, long term mold growth.

2 Install galvanized flashing materials over the weather barrier at all wall openings, penetrations, junctions, connections, window sills, heads and jambs, lapped in such a way that water tracks down on the face of the buildings exterior walls.

3. Install a minimum of 1″ = 1 pound density = R-5, Extruded Polystyrene Foam panels (EPS) using Assembled Polymer Based Washers and 20 gauge Metal Fasteners to attach the EPS foam panels to the buildings wall structure.

4. Now a four step application of synthetic, polymer based, stucco coating over polypropylene fiber mesh should be applied. The fiber mesh gives strength and quality-control of application and the synthetic stucco coating provides an aesthetically pleasing waterproof barrier that won’t crack or de-laminate. The initial rough application of the synthetic stucco and mesh will provide strength and leveling of the rough building structure.

A. Apply fiberglass mesh joint tape over joints where the foam panels meet and coat and backfill the synthetic coating over the joints as well as the screw heads and washers used to attach the Extruded Polystyrene Foam panels.
B. Trowel on a skim coat of the synthetic coating over the polypropylene fiber mesh in order to imbed the mesh into the initial rough application.
C. Apply a second coat to provide additional strength and adhesion.
D. Apply a third coat to provide waterproofing and abrasion resistance.
E. The fourth and final coat is to provide aesthetic beauty and if a high quality, 100% waterproof, synthetic stucco coating is procured, it can be mixed with color in order to avoid having to paint the finished stucco coating.
F. To complete the process, an application of high quality primer and a flexible sealant need to be installed between the interface of the exterior coating and the metal window, door frames and flashings. Because sealing this interface is one of the most important steps of this process, the following precautions should be observed to properly apply the approved sealant. Use skilled tradesmen who have experience with modern synthetic building systems for installation of sealant systems. Follow sealant manufacturer’s installation instructions. Use fresh sealant materials that have arrived at the job site in their original unopened containers. Inspect joint for proper design in accordance with contract specifications, the concrete coating manufacturers published details, and sealant manufacturer’s recommendations, regarding width, depth, location, substrate, primer, etc. Report discrepancies to the responsible professional and correct deficiencies prior to installation of sealant system. Make sure all joints are clean and free of all foreign matter such as moisture, dust, sealers, release agents, paints, etc. before installation of sealant system. Install sealant system only when climate conditions (temperature, humidity, etc.) meet sealant manufacturer’s recommendations. Protect adjacent materials, including finished concrete coatings, from damage during installation of sealant system. Mask adjacent areas as required. Allow concrete coating system materials to cure prior to sealant application. Apply a coat of color coordinated primer into the joint. Allow at least 24 hours to dry before application of the sealant primer. Do not return concrete coating finish into the sealant joint. Install primer, bond breaker and backer rod as specified. Allow primer to cure. Remove primer overspill. Mix sealant per manufacturer’s instructions. Apply sealant with gun or knife as appropriate, using proper nozzle and technique. Sealant should completely fill joint cavity to backer material and be in intimate contact with substrate. Smooth surface of bead after sealant application, as to leave a neat-appearing, smooth, wrinkle-and-sag-free surface without pockets or imbedded impurities, smears or width variations and in total contact with joint sides. Remove sealant from all soiled surfaces. Protect sealant from damage during curing.

The above procedures will cure the exterior water infiltration problems where concrete stucco coatings have cracked. In areas where brick veneer has been installed and on flat window sills, the following work should be contemplated.

The window sills and recessed walls that join the brick veneer are flat and allow water to accumulate which will be an ongoing problem until new sills with fall to allow the water to flow out, over the edge of the brick and down the side of the buildings. With this in mind, sills will need to be fabricated and installed using Extruded Polystyrene Foam and finish them as above.

In the photos provided, the thin brick veneer presently does not appear to be cracking, however if the building was not sealed with a weather barrier before installing the brick, moisture will eventually enter the wall cavity through the brick and its mortar joints and cause the same water infiltration problems. The brick will need the same EPS application and synthetic concrete coating as above. An architect could be hired to design the exterior elevations utilizing the above exterior products in order to achieve a new attractive design that would be 100% waterproof.

In conclusion, buildings should receive consistent maintenance in order to maintain the exterior surfaces. The extent and nature of maintenance will depend on the size and exposure of the individual buildings. As a guide, the following basic maintenance tasks should include but not be limited to:
1. Washing down exterior surfaces every 6-12 months.
2. Re-applying of exterior protective finishes when necessary.
3. Maintaining the exterior envelope and connections including joints, penetrations, flashings and sealants that may provide a means of moisture entry beyond the exterior cladding.
4. Clean out gutters, blocked pipes and overflows as required.
5. Prune back vegetation that is close to or touching the building.
6. The clearance between the bottom edge of exterior sheathing and the finished ground cover must always be maintained.