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I'm repairing the stairs of a deck structure, replacing dry-rot stringers with new ones. The stringers rest on top of a cement pool deck. The pool deck is sloped towards the stairs, so I expect rain water to come towards the stringers.

Is there a good technique to water proof the new stringers? I was thinking using Redguard type of waterproofing but I read that this could make things worst as moisture could potentially be kept in.

The stairs are about 20 feet wide, so I have about a dozen stringers to deal with.

This is what some of the stringers look like after 16 years.

Water damaged stringer

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    I am thinking some kind of galvanized L bracket bolted to the stringer and the concrete. The goal is to keep the bottom of the stringer off the concrete so it does not sit in water. They do not look like treated wood stringers. – Alaska Man Jun 29 at 18:47
  • You want to protect these stringers from further damage or you want to protect new stringers? – MonkeyZeus Jun 29 at 18:47
  • @MonkeyZeus new stringers, I'm replacing all of them. – Georges Jun 29 at 18:48
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    @MonkeyZeus in theory there should not be standing water because the cement deck slopes so water can drain in a channel. In practice, I just noticed after last night rain, there is some sort of low spot and the water has been pooling right there. It's only about 1/16 deep, but we do get a lot of rain here in Hawaii. – Georges Jun 29 at 18:53
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    Wood is wood, it's gonna rot. Considering they are 16 years old I'd say they look pretty good. Anyways, your new stringers should be pressure treated and have them cut short so that they are elevated 1" inch off the ground. Cut shims out of composite decking, glue them to the bottom using a polyurethane construction adhesive and nail them using galvanized nails – MonkeyZeus Jun 29 at 18:53
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I had a similar problem with stringers in direct contact with cement that had water runoff. I sawed off 1/2" from the bottom of each of four stringers,screwed in 4- 2 1/2" stainless steel lag screws into the bottom of each stringer. Once back in place, backed out the lag screws like leveling a washing machine. End result, the stringers were 1/2" above the concrete and the water just drained by. I guess it's kind of a hack but it worked great. Twenty stringers is a lot of lag screws though.

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  • Interesting idea, how many years did that last? Did the foot traffic loosen things up? – MonkeyZeus Jun 29 at 19:33
  • @MonkeyZeus Going on 30 years. They replaced some stair treads but the stringers were OK. The traffic never loosened up anything, why I went with the 2 1/2 screws. – JACK Jun 29 at 19:50
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    I would imagine that pre-drilling is a good idea for lag screws or else you run the risk of splitting the stringer across its length? – MonkeyZeus Jun 29 at 19:59
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    @MonkeyZeus I did predrill but not all the way... wanted to leave a good "foundation" and knew i'd back them out a bit. – JACK Jun 29 at 20:24
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    Great idea and it makes it very easy to get the bottom of the stringer cut to precisely match whatever ground it's sitting on. Since it's not actually sitting on the ground. – FreeMan Jun 29 at 20:45

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