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Story
It had been a few years since we had power-washed our deck. Though I was not that concerned with the visual appearance during that time, what I was missing was the importance of doing this regularly for structural reasons. Power-washing not only cleans the surface, but removes the debris that accumulates between the deck planks. As the debris sits there it rots, and where the joists cross the planks, the rot is directly going toward the supporting joist structure.
I found this out the hard way. There were a few adjacent boards that were sticking up a bit. I could have assumed was that the screws came loose and just needed to be screwed down. However, I knew these screws were 2-1/2 inches long with most of that going into a 2x6 joist. If the boards are not sitting flat, then that could only be because the structural integrity of the underlying joist was compromised and there was nothing left for the screws to bite into.
We would find more more rot than I expected, and would only repair the worst parts. It is only a matter of time before more structural work would be needed, but this is the story about the limited repairs we did do this time around.
Demolition and Assessing the Damage
First plank removed.
From the loose boards, there was some hope that only one of the joists affected. We had to pull up a number of deck planks to get at the known bad joist, but that revealed that adjacent joist were also in bad shape. The scope of planks to be removed kept expanding as we went.
While some of the screws came out easily, most of them did not and needed to be drilled out. This was the fault of the installers who did not countersink the holes and had the torque dialed up too high on their screw guns. These are stainless steel screws, so corrosion was not an issue here.
Extracting screws.
Removing screws from boards with vice grips.
The deck planks themselves were is good shape. These are Ipe wood, which is quite durable so we would be reinstalling them after fixing the structural parts. This meant we needed to remove all the screws and do it as non-destructively as possible.
When needing to drill out the holes, we would not be able to use the same holes when we reassembled them. We would need to fill the old holes and drill new ones. You have to pre-drill the holes because the Ipe wood is very dense.
The known problematic board was indeed bad with significant rot. We found three others adjacent to it that also had significant rot. One of these was a major long joist that would have required tearing up most of the rest of the deck. We decided to just cut out the worst part of this one and leave the rest even though it was not in great shape.
View of rotted boards after plank removal.
Worst rotted section (closeup).
Rotted joist section.
Board rot by plank gap.
Old rotted structure (view west).
Remaining planks with old rotted structure (view east).
Installing New Joists
It was a moderately difficult decision on exactly what joist to cut, where to cut them and how to install new structural members. I did not want to do anything overly complicated, but needed to ensure it would be somewhat structurally sound.
I also decided to add some extra 2x4 pieces to the 2x6 joists so I would have more area to screw down the planks. I would need more flexibility on where to drill the holes since I could not reuse the previous ones that were drilled out.
Installing first new joist.
First new joist (north end).
Joist anchor installed.
The most complex joist was the long one that was only being partially replaced. I needed to "sister" the new 2x6 onto it, but it was rotted and soft in spots. Also, since this will keep deteriorating, the joist failing is a real possibility in the coming years. To guard against that eventuality, we used some round concrete blocks underneath it so that if it does fail, there will be some extra support to make it not so catastrophic an event.
Clamped new boards on old rotted board.
Supporting concrete blocks (closeup).
New structure in place (view northeast).
Here are some views after all four rotted joists were replaced.
New structure in place (view south).
New structure ready for joist tape.
New structure in place (view southwest).
Joist Tape
Joist tape closeup.
The fundamental issue that leads to all the rot we saw was debris sitting on top of the joist in between deck planks. This is always going to happen to some extent even if you clean it regularly. What I stumbled across in my researching deck repairs was a product they call "joist tape". It is just vinyl tape you put on the upper edge of the joists and then lay the planks on that. This prevents any accumulated debris from interacting and rotting the wood. Genius.
Or maybe this is obvious, I am not sure. What I do know is that if this product existed when my deck was built ten years ago, then it was criminal that this was not used. I have not heard of any downsides of using this, and it is not expensive, so there is no excuse not to use it. It is mostly the same as electrical tape only slightly wider and with a gritty surface to keep the planks from sliding (I guess).
Joist tape installed.
Joist tape installed (view northwest).
Concrete blocks suporting new structure.
Deck Planks
All boards put back in place (prior to screws).
I had marked all the boards before removing them so we could reinstall them in the exact same places. We put them back down and then went through the process of re-attaching hundreds of screws.
I had three drill guns going to make this more efficient. A high torque corded one was used to drill the screw holes in the planks, an old, crappy corded one used to countersink the hole and my cordless drill gun for driving in the screws.
We would fill the old holes later, but there was also some sanding necessary to remove the jagged parts the screw removal process left.
Final Result
After sanding, filling the holes with an epoxy wood filler, we then oiled our deck for the first time in a few years. The wood filler had a high contrast, but I knew it would quickly darken from normal usage. You can hardly see the wood filled patches after a few months.
After holes filled and deck oiled (view east).
After holes filled and deck oiled (long view).
After holes filled and deck oiled (closeup).