replacing deck joists

[Bigbartguy]

hi folks

I'll try to summarize this as quick as I can. My cabin's previous owner built a deck using UNtreated wood and then dropped a 4 season porch on a good portion of it.

under deck - the decking and joists are now rotted. I can dig into the joists w/ screwdriver. very wet wood.

under 4 season porch - everything still looks ok.

-Can I just drop new joists next to the old ones and leave the old ones in place? I'd still cut out the rotted parts under the deck, but leave the 'good' portion under the porch., just because trying to get them out would be a huge undertaking. The new joists would support the porch as well

hope this makes sense? & thanks!

[nitroant]

I would have to see this in person to say for sure, but as long as you replace the joist with a same sized joist or larger right next to it before taking out the rotten joist it should work. Sounds like you know to use treated wood this time. As far as the stuff under the porch goes, well, its good to get new stuff under there too, does the old stuff need to come out?? Not sure I can say for sure. There is a chance that the old stuff will trap moisture against the new stuff and you could have another rot problem on your hands, but down the road a ways. Good luck and be safe.

[Bigbartguy]

thanks Nitro. You're thinking just as I was about the trapped moisture. I'm pretty confident that the portions under the porch are good but I'll double check.

I def. know to use treated wood. The previous owner also used NONtreated wood for the decking, butted them all up so no water could drain, and then painted them green!!!

I guess he thought that meant that he 'green treated' them!

grrr

[soldoncass]

If you want a permanant fix, it sounds to me like the deck needs to be removed and replaced completely, including the deck board on the wall and the posts and beams if they aren't green. Doing it right from the bottom up may cost more in the short term , but much less in the long term, and you won't have to think about it every year for the next 20, wondering if it is safe. As far as the 4 season porch, it probably will be o.k., as long as it is protected from water and outside air. It should be insulated underneath and covered . Maybe not what you wanted to hear, but that is the bottom line.

[eurolarva]

Check with your lumber yard about using Zmax fasteners and hardware. I built a deck two years ago and it was real easy to get the wrong stuff back then. The Zmax is double dipped zinc that will not be affected by the new pine treatment. How high is this deck above ground? My guess is if he did not use treated wood he probably did not do correct footers for the posts. Here in the twin cities if deck is over 6 ft above ground the footers have to be at least 1 ft diameter and like 42 inches deep and the posts have to be 6x6 not 4x4

[Bigbartguy]

he used 4x4 posts, sitting on footings that are made out of pvc pipe & concrete, about 4 inches across.

I'm tearing the entire deck down and leaving the old footings in (it cant hurt) and installing proper footings and posts as well. I'm pretty much rebuilding the whole deck for safety reasons. It's difficult because I have to support the porch while I'm doing it.