What Are The Most Important Potential Leak Areas When Constructing Or Replacing An Exterior Balcony Deck?
The critical areas of a 2nd floor exterior balcony deck:
1. Minimum ¼” per foot slope away from house to finished edge of deck.
2. Out-swing exterior doors with bumper thresholds or horizontal sliding glass doors, both with metal drain pans.
3. 4-6” step down from the finished floor to the top of the deck.
4. Minimize or zero deck penetrations.
5. Anti fracture membrane between floor tile and waterproof membrane.
6. Concrete balustrade with large drainage scuppers.
7. Support columns wrapped in self sealing peel and stick with sealed, precast caps.
8. Light colored tile to minimize expansion and contraction movement in the flooring.
9. Gutters and downspouts on roof areas above balcony deck.
10. Proper drainage plane behind stucco on vertical walls adjacent to deck.
11. 12” of waterproof deck membrane extending up the adjacent vertical walls with over lapping drainage plane from above wall.
12. Expansion joints in tile flooring max 400sf and length to width ratio 1:1.5.
13. 2x10" floor joists with ¾ “ T&G plywood subfloor, glued and screwed to joists.
14. Suspect all penetrations of adjacent vertical walls such as light fixtures, electrical outlets, hose bibs, Windows, doors etc.
15. Roof overhangs that protect the doors from weather.
A more detailed explaination:
1. The slope on the finished deck must be equal or greater than ¼”/ft per the building code and manufacturer requirements.
2. Out swing French doors with positive sealing bumper thresholds are a must. Along with metal drain pans installed under the doors. Any penetrations to the pan must be meticulously sealed with zero penetrations a big plus.
3. Due to local heavy rains and strong winds a 4-6” clear space between the interior floor and the finished deck level is required.
4. The more penetrations to the finished deck the more opportunity of future leaks. Surface mounted deck railings are a source of future leaks. Recommend concrete balustrade installation that sits on top and grouted to the tile decking.
5. An anti fracture membrane like Schluter “Detra” is a must with tile flooring.
6. Precast concrete railings normally comes with wide drainage scuppers that allow the deck water to drain quickly.
7. Support columns to hold up the balustrade must we sealed with a heavy peel and stick material, builders felt, wire lath then stucco. The lath fasteners will self seal by the peel and stick. Since the precast column caps are pours recommend applying 3 coats of clear sealer.
8. The darker the color of the finish flooring tile the greater the expansion and contraction. A black color is never recommended.
9. Keeping as much water off the deck is the goal here. Gutters and downspouts on the roofing areas above the deck is recommended with downs spouts directed off the deck rather than on to it.
10. Paint and stucco over frame is not waterproof, that's why the membrane (house wrap & building felt) behind the stucco lath is so important. That’s what we call the drainage plane. If the SF of vertical walls adjacent to the deck is limited, installing a self sealing peel and stick material would be best.
11. A high velocity, wind blown rain can cause water to back up into the living space and behind the stucco. Running the waterproof deck membrane up the vertical walls 12” prevents water from getting behind the stucco. Make sure the lath and weep screed fasteners are 6” above the finish floor of the deck.
12. Tile expansion joints per manufacturers recommendation. The tile work is going o expand and contract so providing flexible expansion joints will minimize tile cracks.
13. The subfloor supports the weight of the deck materials. 3/4” T&G plywood, set on 2x12's, performs better under potential moist conditions. Glue and screws addresses the possibility of the fasteners backing out and penetrating the waterproof membrane from below.
14. As I mentioned earlier, we are looking at pin holes that may cause a deck leak! Homeowner’s usually do a poor job maintaining there homes. Smart Custom Home Builder’s look ahead to prevent future issues.
15. Exterior doors are definitely a weak point and one of the first places to leak. Having significant protection from the weather is vital. A minimum of a 2' roof overhang in front of the doors is recommended as long a the overhang is only 16" above the top of the doors. If that distance is greater, even more overhang protection is required.
As you can see, there are a number of critical deck issues that can go wrong and above are only the most obvious. Exposed decks are not for risk adverse Owners or Builders.
Have an awesome day!
Mike
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