nsulated cavity walls can be constructed by building the backup wall first and by building both wythes simultaneously. Is either approach better?
Depending on the project's construction sequencing, there may be an advantage to using one approach over the other. Walls can be built to work properly either way, but it's more difficult to create a free-draining cavity when both wythes are built at the same time. This is because special care must be taken to prevent mortar bridges from being formed. The backup and the veneer wythes normally are built to a height of 16 or 24 inches. Rigid insulation is placed into the cavity followed by a row of ladder-type bed-joint reinforcement. Unless care is taken, however, mortar can fall and collect on the previous course of the bed-joint reinforcement and on top of the insulation below. This can form a mortar bridge that interrupts the flow of water in the cavity wall.If the block backup wall is constructed ahead of the veneer masonry, insulation can be placed on the face of the backup masonry and taped. Tape also seals around ties that extend through the insulation. The taped insulation creates a barrier that prevents water from reaching the backup wall.