cantilevered deck rotten and needs replacement

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  #1  
Old 08-03-03, 06:38 PM
windfall96
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cantilevered deck rotten and needs replacement

The deck off my bedroom is cantilvered 4 ft. The house was built in 1980 and the deck joists are sistered to the main floor joists for the second floor. The joist are rotted on the top surface and I am replacing the joists and the decking.

I will remove the ceiling in the room below the joist to gain access. This appears easier than attacking the subfloor/nails on the second floor. I plan to TRY to un-sister the old joists and sister new. Spent the day removing the wood which covered the joist spaces on the outside of the house. Surpriced that the deck oist are already sister to the main floor joist in lieu of just being an exrtension.

Looks lid a big job to try and seperate the old sistered deck joists (which by the way run the full length of the room to the opposite wall).. So I am thinking of still removing the ceing in the room below, cutting of the rotten guys flush with the floor joist and add new sistered joist (now there will be three) for the new construction.

SWOOOO the questions
Is there an easier way?

My limited understanding says that the 4 ft cantilever will be ok if I double the distance into the house. IE a 12 ft joist with 4 ft overhang and 8 ft sistered to the existing joists?
 
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Old 08-03-03, 07:04 PM
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windfall96,

Rule of thumb is the cant must be 1/3 the distance of the total joist so a 12' is in order. Basically, 4 foot cant and 8 foot secured properly inside. I would suggest getting long sawzall blades and use this to cut the nails that hold the existing canted joists. Then this can be removed easily. Make a vertical cut just inside where you can drop the rotten one down would be ok. Get extra blades as this will damage them quite fast.

When I say I would suggest this...I mean that even though you remove these rotten ones, you may have nails or other type of fasteners protruding through the subfloor of the room above. Not an easy thing removing this other than a metal blade for your sawzall, wear gloves as this will become a knuckle buster!

It's an issue that you can consider if you don't want to remove the rotten ones for the reasons above but adding another on the opposite side is acceptable. Once you got these all in place, fill in your ends and seal it up right.

Good Luck!
 
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Old 08-03-03, 07:40 PM
windfall96
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Thanks for the quick reply. I had also thought of the subfloor above nailed into the joist I was try to remove. I was hoping for the best BUT I may take the easy way out and just do a 3rd "beam".

When you said "seal the ends" what did you mean? the deck boards / and joist rotted on what was exposed (the top surface). in fact although the decking was decently painted, I was surprised the joist rotted so quickly. Is there a good way to seal the TOP of the exposed joists. I will be using pressure treated lumber which was NOT used in the initial installation. I was thinking of deck staining the top surface of the new joists prior to puttin on the new deck. Was that what you were referring to??? Is their something better??
 
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Old 08-03-03, 10:19 PM
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windfall96,

Since the cantilevering means that the joists which support the deck boards penetrate through the skin of the house and attach to the parallel joists that support the floor, these are great places for water infiltration to occur.

This almost always means that the deck outside will be at exactly the same level as the floor inside. This is not ideal, since it is desirable to have about a four-inch step down at the doorways. This prevents rain and accumulated snow from penetrating under or around the threshold of the door.

Since this is true, the house joints at the deck joists are vulnerable to water. Usually this intersection will be protected by building in a piece of flashing extending above the siding at the deck intersection (impossible at the threshold) and out over the tops of the deck joists. The sides of the joists should be heavily caulked. Often, these intersections allow water to penetrate the house. This a favorite haunt of carpenter ants.

Standard dimensional lumber that extend out from a building can be a "magnet" for rot being drawn back into the building along the cantilevered framing members that extend out from within the building framing itself. These decks deserve extra special inspection on any home more than five to ten years old.

All I meant was to ensure that what you have is properly flashed and caulked to avoid problems. You're absolutely right about using something like W/T , Cedar or Redwood to avoid rotting lumber. Apply flashing over the canted area and ensure that flashing is placed under the siding and over the joists. Use silicone caulk at house wall. When installing your decking, assuming you have placed flashing over the entire canted joists, apply a bead of caulking over the flashing so this prevents water infiltration from leaching back to the house wall area after you apply your fasteners.

Don't waste your time staining the deck joists, proper flashing will ensure years of enjoyment. If possible place the new canted joists at a slight angle downward from home, this is added protection against water moving back towards the home. Maybe 1/4" down at end. The angle can be very slight and will not effect the use of the deck area.

Hope this helps! Good Luck!
 
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