New Deck over Old Deck?


I just purchased a home with a deck. The previous owner built a new screen room on top of the 20 year old deck without doing anything to renew the deck. I have tried pressure washing it but the boards are in poor shape. Turning or replacing the deck boards is not an option without dis-assembling the entire screen room. Can I purchase 5/4x6 PT boards and just install them on top of the old deck? If so, how long would I have to wait before I could stain them considering they are shaded by roof of the screen room?
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I just purchased a home with a deck. The previous owner built a new screen room on top of the 20 year old deck without doing anything to renew the deck. I have tried pressure washing it but the boards are in poor shape. Turning or replacing the deck boards is not an option without dis-assembling the entire screen room. Can I purchase 5/4x6 PT boards and just install them on top of the old deck? If so, how long would I have to wait before I could stain them considering they are shaded by roof of the screen room?
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If it is just a screened in room that means that water can blow in onto the floor boards. If the new boards are nailed down directly onto the old ones, water will be able to penetrate between the boards and stay there to encourage warping and worse mould, mildew and rot.
If you have enough height clearance at doorways, you possibly could rip some strips of pressure treated or weather resistant wood about 1/2", 3/4" or 1" thick, and nail it down over the old floor right over the joists under the old floor. This will provide an air space to prevent water from being trapped. Your new floor could be laid over the strips nailing or screwing through to the old floor.
If you do not have the height to build up the floor properly, you may have to saw around the walls to remove the old boards and replace them with new ones. It may take some creative solution to cover up the remnants of the old floor at the walls where the saw cannot cut very close to the walls.

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Yes, water can still blow in onto the boards. I do have enough room under the threshhold of the french door to build up the deck. Would the existing gap between boards provide enough ventilation for drying?
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Not with nailing new boards in contact with the old. Sure fire recipe for mould and decay. If you space the boards away from the old ones as I described you would have a space to allow the wood to dry out, but it still could be a problem with dust, dirt and insects filling in the space with moisture holding debris.

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Get yourself a HEPA face mask and and sander and refinish your "floor."
It will look BETTER than a new deck when you are finished.

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