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denemante 09-17-2012 01:27 PM

increase deck size with minimal construction
Hey all - I had a similar thread, but wanted to clairfy and exapand on it a bit. We have a classic 12x12 deck that's about 14 years old. It's about 10 feet high. Still very structurally sound, but needs new decking/balusers/railings.

Question 1: I can look at the joists - they look good to me. A little grey and a tad of green on them - but no rot. If I screw a deck screw into them - it doesn't quite feel the same as if I drove a screw into new lumber, but goes in strong nonetheless. So given that they are 14 years old, I presume they have deteriorated some. But any reason why I shouldn't reuse them? Any rule of thumb there?

Question 2: The deck goes out 12 feet from the house, where it's supported by 3 8x8 legs with a header atop them. Could I extend the joists farther out from the house with extensions? Like I might cut a 4 foot long 12x12. Then lay it flat up against an existing joist, with a 2 foot overlap, and bolt it in place. So it would stick out 2 feet farther away from the house than my current deck.


GBrackins 09-17-2012 02:21 PM

check this out, it may answer some of your questions, it is the American Wood Council's "Prescriptive Residential Wood Deck Construction Guide based upon he 2009 International Residential Code.

I would not do as you propose, see Table 2 of page 3

Good luck!

AndyGump 09-17-2012 02:39 PM


I would not do as you propose
Let me hear an AMEN!!


robertcdf 09-17-2012 06:58 PM

Another vote for NO to what you propose. What do you plan on putting on the joists? is it going to outlast the frame? It would be quite silly to install a decking that will outlast the frame, and being that the frame is already 14 years old anything except DF is going to outlast the frame.

denemante 09-18-2012 03:57 PM

1 Attachment(s)
Hey all - thanks for the replies. I neglected to mention - we don't use the deck because the decking and railing are crappy, loose , warped and look bad. At some point down the road (2,3,5 years perhaps) - we will probably go with a totally new, different style deck.

But until then - I can't leave it like it is. So I'm hoping to drop about $350-$400 into it to get me through the next bunch of years. I don't expect this to be a 15-20 year solution.

In regards to the link GBrackins posted - I don't quite understand it. I read it as something like total length of a joist you can use per wood type.

See attached illustration I drew. This is what I was thinking. Since I'm redecking and putting new railings on anyway - I figured for somewhat minimal cost - I could pick up perhaps 2 more feet out from the house.

It seems like a logical solution. Plus - with my current joists being 12 feet -if that's some kind of limit - I'm not going over it with that single board - I'm bolting a new board to each joist to extend them out.

I think it would be plenty strong. But my worry is that there might be some weight load issue where it's now too heavy (although supported by 8x8 legs with headers under it). Or, perhaps at that greater distance from the house, side-to-side movement woudl be amplified causing sway and wear on the construction.

Note that the original deck is 12x12 feet and there are actually 10 joists, not 4 as pictured.

AndyGump 09-18-2012 04:14 PM

Though I am not a licensed PE or SE, I am considered a design professional only because I have designed to prescriptive codes for various areas and have had my designs O.K.ed with the governing authorities in a very limited scope.
From your latest description it seems to me that the existing deck is not built to code I think even code as far back as about 20 years. IBC, IRC or UBC.
It is possible that if you dismantle the existing deck and re-use much of the deck material by using new, properly designed joists and beam and connections for not too much more than you are thinking of paying for the "Rube Goldberg" attachments.
I do not mean to be insulting at all, it is just that anyone in the trades that knows anything at all should not give you encouragement in your design idea of this deck structure.


denemante 09-18-2012 04:26 PM

Thanks for the input - as such I'm leaning away from my extensions!

Aside from that - any problem just removing the decking boards and balusters/railings and replacing? As noted -those have taken the brunt of the weather. The joists and legs still seem rock solid. Again - my goal is to have a nice-looking, solid deck for the next 2-5 years.

allthumbsdiy 09-18-2012 07:45 PM

Last thing I would want is to fall off from a 10' high deck.

If I wanted to stretch out the use of my existing deck for another 2+ years with minimal expenses, I would consider:

1. flip the existing decking to see the other side (underneath) is in good condition;

2. replace guard rail posts and mount them inside the rim joist (you will need to modify your deck slightly) with 2 ACQ approved bolts/nuts/washers. For added rigidity, add in solid blocking (or buy brackets)

3. replace top and bottom rails and install new balusters (again, mount them inside the rails for max. protection).

As far as extending your joists, I think you will find that you will lose your grandfathered status and will have to bring your old deck up to current code. Ask your building inspector to confirm but at that point, I think it would make more financial sense to just spring for a complete new deck.

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