Q1: We are a concrete repair contractor that has been working on several deck coating failure projects in the southeast United States. Specifically, we have seen coating failures propagate from the deck coating/window wall system interface on high-rise cantilevered cast-in-place concrete balconies. We are finding that the deck coating is prematurely failing along the sealant joint at the base of the door/window wall system. The increased moisture penetration due to this failure is causing further deck coating failures and subsequent deterioration to the underlying concrete substrate. Many of these projects are less than five years old, and I am curious if this type of failure is common in the industry and, if so, what might be the cause of the failure.
A1: Due to code-required accessibility requirements for exterior balconies on high-rise buildings, READ THE REST BY CLICKING TITLE ABOVE
The balcony I’m repairing has cantilevered joists extending into the framing. The siding and some of the wall sheathing around the joists have decayed. I’m afraid the rot may extend into the floor blocking and perhaps beneath. I can deal with the structural repairs, but what is the best way to flash the balcony joists to prevent water leaks? All the original builder did was caulk between the siding and the joists. —Daniel T. Browning Essex, Conn.
Mark Marsch has over 14 years in waterproofing consulting and support services on multiple projects.
Here is an excerpt from Mark’s article on flashings for Tile Decks
1) Sheet metal
Because sheet metal is installed first, it is critical to the complete tile assembly. Setting up the proper elevations for the full tile assembly should be done prior to any metal installation. Sheet metal should be installed at all deck transitions. Since the sheet metal contractors are not familiar with the waterproofing requirements nor are they responsible for the tile elevations, it is critical that they be given direction. All of these transition details can be prefabricated prior to installation in the field. The architect will usually specify soldered corners on all prefabricated items.
The waterproofing manufacturers, since they do not sell nor do they warrant the metal, require that the installation at least follow SMACNA (California Association of Sheet Metal and Air Condition Contractors, National Association) guidelines. Merkote Products is the only manufacturer that I’m aware of that provides its customers written direction on metal details. You can find these details atWWW.merkote.com under Mer-krete systems. For our applications on an exterior deck, the nailing patterns are minimum 3in. on center in a staggered pattern with a minimum 4 in. overlap between metal pieces. All overlap joints must have sealant (a single component urethane is recommended) between the laps.
The metal laps should always follow the same lapping procedure as you would use with sheathing membranes on walls. Since some decks have the slope built into the framing you want to start at the lower end and lap over the lower pieces as you would do with shingles.
READ MARK’S WHOLE ARTICLE BY CLICKING ON THE TITLE ABOVE.