Just To Say Hi And Ask A Question - Floor Joist Spacing

Old Sawdust

Hello to each of you

I've been reading your forum for the last several hours and have enjoyed many of the exchanges.

I have been in the remodeling and repair business since the early 70's and appreciate the CRAFTSMANSHIP seen here.

I've never seen the problem I'm up against with this new client. Don't even have a clue as to how this deck received a CO, unless of course someone in days gone by built it after the fact.

Anyway there are 3 decks that run the length of the home and the floor joist system is PT - 2 x 8 - 16" OC & the decking is 3/4" cedar. I've looked and looked but can't find any information on what code says.

In speaking with the cedar salesman he tells me that code would require 12" centers. This sounds appropriate to me but I've no idea for sure. What I'm considering is placing an additional joist between each existing joist. Certainly this would give adequate support.

Problem is the decking system cannot be changed to 2 x material due to door thresholds being against the existing decking so 3/4" is my max. Even considered plowing a trough in 2 x material but know that this is not going to accomplish much especially if the "joints" were not TIGHT. So the only option seems to be 3/4" cedar - painted. Which is what she has now.

When constructing a deck my usual construction method is 2 x 10 pressure treated joist on 16" centers with 2 x material or 5/4 material but in my 40 + years of doing this type business I've never run across this problem.

I joined this forum in hopes that someone might have an answer, and now that I've been here for a while I've come to really enjoy the camaraderie and exchanges.

Probably like the rest of you my time is limited but this seems a great place to come and listen to the conversations.

I hope this is the correct place to ask my question, have no intention of being our of place but was not sure where to post.


Thanks
Old Sawdust
aka Reeder

if it make a difference I'm in the Atlanta area

genecarp

Welcome Saw,, not exactly sure what your question is, my response to your post is that the code does not matter, clearly 3/4'' mat cannot be used for decking with 16'' centers. I would do anything i could to avoid using 3/4'', raise the door!!!!. if you must use 3/4'', 12'' centers for sure.

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curapa

Hi, thanks for introducing yourself. There is a fence and deck section under carpentry.

As for your question, I have never used cedar decking so I do not know what spans the 3/4" can run.

For the cost of cedar I would suggest using a 3/4" composite like Evergrain

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genecarp

Good option, however evergrain is 1'', most of the composites are 1'' to 1 1/8''. if he could get it in, its the way to go. G

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dirt diggler

yeah, what they said ...






(that's my "general contractor's response")

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Thanks in advance!!!

neolitic

¾ T&G fir or TYP, back primed and painted.

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genecarp

good call

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Old Sawdust

Thanks to each of you.

My question was what does code say about floor joist spacing center when using 3/4" material - sorry for not being more clear.

The T&G Option might me a good one if the fall is OK.

I will post my question in the appropriate place . thanks for your suggestions and willingness to share you knowledge.

Reeder

woodworkbykirk

sounds good to me

reveivl

I don't know what your code says, but if you double up on 16" centers, you're looking at 8" centers, the cedar is actually spanning only 6-1/2". If it's halfway decent material I can't imagine anyone but the most retentive BI whining about that. Then you go over his head and get an engineer?

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SLSTech

First off welcome to CT - I would not consider a salesman a code expert, I would contact your local code office if you have questions. Codes enforced vary for each jurisdiction. I have not done a cedar deck so I don't know if the joists should 12" or 16" OC for best performance.

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neolitic

Porches are done with ¾ T&G
over 16oc all of the time.

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woodmagman

I find it rather interesting that ¾” is not acceptable as an exterior finish, but it is as a interior one and running it diagonal to joisting is very common for sub-floor. Yes cedar does not span as well as fir but it has been used in homes for sub-floor and this is interesting to me…

cleveman

The cedar used here for decking is 5/4", but I wouldn't have a problem with 3/4" if you do a bit of selection and avoid bad knots, etc.

Is the 3/4" material decking or just general purpose cedar (trim material)? I would think you'd want to round the edges a bit if it is just common stock.

I can get common white oak for $1/bd foot here and have thought of making a deck out of it just for fun. It would be a lot of work to joint and rip the boards to square up the edges, then round them over a bit. I also don't think the color would look well over time, as I think it just turns dark gray.