Waterproofing*
The * in the title is a disclaimer regarding the term “waterproofing” noting that it is really misused. There is nothing in the construction industry that is truly waterproof. There are conditions, primarily due to weather, that limit a product’s ability to claim that it is “waterproof”. Water consistently seeks to penetrate all construction materials and all buildings. At some point water tends to win. Therefore, any product that claims complete waterproofing should be further investigated. It is far more accurate to use the term “water resistance” when discussing the management of water penetration.
Water Resistance
There are several steps that should be followed when concrete block of any kind is going to be left exposed without any paint, stucco, or veneer coverage over the block. If any of these products are used and installed properly then the block wall should qualify as a water resistant membrane, protecting the building construction from any water penetration.
Thousands if not millions of concrete buildings have been built in the past 100 years or so and have either been painted, stuccoed and painted or veneered with a vast array of products (ie. siding, brick or stone) with very satisfactory results. That said, a crack in the stucco can allow water to begin penetrating any type of wall construction. This situation typically goes from bad to worse and eventually will need corrective repairs.
Exposed Block
The definition of “exposed” as it pertains to concrete block is when it is left completely exposed in its natural state to the elements. Concrete block consists of aggregate (quarried and washed stone pebbles, scoria, pumice or the like), cement, possibly lime or other natural binders and water. These materials are all inorganic and vary from from region to region but ultimately reputable block manufacturers have determined the appropriate structural formulae. These are called “mix designs”. These materials naturally absorb water and when molded together into concrete block will allow water to “wick” (slowly absorb) through the block. Even though the wicking process is slow, it is normally not resistant enough to deter a wind driven or climatic soaking rain.
Integral Water Repellant (IWR)
As manufacturers and distributors of concrete block, one of the first things that should be determined is whether or not the block will be exposed. If it is going to be exposed, further protection is required. The first step is an integral water repellent (IWR) chemical is added to the mix design. This IWR additive greatly increases the resistance of the materials absorbing water. The cost of this additive varies from region to region but adds about 10% to the cost of the block. One commercially available additive specifications can be found at this link. There are many additives available. The local / regional block plant determines what additive they elect to use.
Since the block wall consists of concrete block and mortar, the mortar must also include an IWR additive. Masons must mix the IWR in appropriate amounts to also protect the wall assembly. One commercially available additive specification can be found at this link. Although there are many additives available, it is strongly suggested that the mason use a compatible additive to what is in the block.
Flashing
Omni Block is technically a “single wythe” wall assembly. This simply means that there is one block between the exterior and interior of the building. Even though the unique design of the actual Omni Block block’s cells are filled with molded Expanded Polystyrene (EPS) inserts they are NOT mechanically attached to the concrete block. The installed inserts have micro gaps between them and the concrete block along with designed flutes that effectively allow the assembled wall to “breathe”. The design allows for moisture (not a floodgate) to move down the wall due to gravitational pull.
Flashing trays with drain spouts are placed at the bottom of the block wall (above the foundation) that will capture this accumulated moisture and allow it to drain out to the exterior. Blockflash flashing is recommended due to the product advantages, its ease of installation and effectiveness. Other flashing systems may be used as well.
One of the advantages of Blockflash is that it is aesthetically acceptable and hardly noticeable in a finished exposed block wall.
Sealers
The application of a commercially available block sealer is the final protective process to make exposed block as water resistant as possible. There are many options available from a variety of manufacturers. Sealers should be applied towards the end of construction or possibly after the complete construction (even after occupancy in some cases). Sealers are either liberally sprayed or rolled onto the exposed block (exterior side of the block is all that is required). Sealers typically do not change the color of the block nor the sheen of the block texture. They consist of a penetrating silicone(s) and once applied do not diminish their effectiveness over time.
The sealers listed below are products that have successfully been used to eliminate water infiltration. Most come with a 5-year warranty. The end user should determine which product meets their specific needs.
Prosoco WS Siloxane PD Sure Klean
