Deck repair question

[tvgordon]

Hi guys,

I have a deck that extends out 8' and only attaches to the house, in other words there are not any posts holding up the deck.  The deck boards that are not protected by the eves of the house have started to rot.  I plan to rebuild the deck at some point, but for now I would like to repair it. 

How do I go about repairing the 2x8 supports without replacing them?  I was thinking of bolting another 2x8 up to them, but since the deck is only supported at the house I'm not sure about adding the extra weight.  I also though about just replacing the deck boards and using longer screws to get down to solid wood, but I'm not sure how far down that is.

Another thing a little unusual is the deck floor boards are 2x4 cedar.  The house was built in the 60's and the deck was part of the design.

Any repair ideas?

Thanks for the help,
Tom

 

[Bob D.]

If I am understanding what you are describing you have a deck which extends out form the house 8 feet and is supported only by 2x8 joists cantilevered out from the house with no additional support in the form of posts or braces.

And, that this deck is in need of replacement or repair, and you believe you may need to use longer screws to reach solid wood as you describe it in these 2x8s.

Is that correct?

Can you provide a photo which will help us all visualize your situation better.

 

[tvgordon]

Yes, that is correct.  The outer 4 feet of the deck that is exposed to rain and sun is what needs repaired.  I was going to sister some 2x8x8's to the existing joists to have solid wood to attach the deck boards, but I'm concerned about adding the extra weight to the deck. 

I'm still thinking of using long screws to attach the deck boards to the existing joists or possibly just attaching 2x8x4's to the existing joists to save weight.  They are 16" apart, so I might be able to get by without having to sister each one.

As far as photos, I've been a member of this forum for years and haven't had any luck getting pictures to post, but I can take a few and try.

Tom

 

[rizzoa13]

I'd probably sister new 2x8 cedar boards. If you used pressure treated to sister you'd be adding significant weight. Can your deck handle that weight? Don't know, but I'd try to keep the additional weight down if possible.

Are the cantilevered framing members also the floor joists for the interior of the house? Is the ceiling finished underneath that floor? I'm actually curious because to really rebuild it correctly you'd need to slide in as long of a board as possible and bolt it to the existing ones. Either that or support the outer edge of the deck back and down to the house on an angle.

 

[JBag09]

If it is cantilevered, for every foot it extends beyond you need two feet inside was the rule of thumb a boss taught me a long time ago, but to go back 16ft is almost as strange as them going 8ft out with no supports.
Personally, I'd put some support underneath, maybe a foot or two back from the front and then sister your joists. But I tend to overdue stuff.

Sent from my iPhone using Tapatalk

 

[kevinculle]

The 2:1 cantilever rule for joists is correct and that makes this deck quite unusual; an 8' cantilevered deck using 2x8 joists (equivalent to a 16' span between supports) seems to be well beyond published joist span tables and possibly the structure was not properly engineered in the 1st place.  An easy fix would be to add outer supports, address rotting joists and end up with a more conventional structure.  If you want to keep the cantilevered structure I would strongly recommend consulting a structural engineer as there are real risks to you and your guests if this is not properly resolved.

 

[tvgordon]

Thanks for the advice and comments, but my way of thinking is that this thing has been on the house for 50+ years so I would say it was designed and built right.

The deck joists do run the same direction as the floor joists in the house which run the width of the house - 40'.  I've looked inside and outside and can't see how it is attached.  I will find out when I rebuild the deck sometime in the future.

I do like the idea of sistering a cedar board to save weight, but an internet search came up with only sistering to the section of the joist that was showing some rot.  If that is safe, I could just attach a 3-4 foot section of 2x8 which would give a solid board to attach the deck boards and not add as much weight.

Thanks,
Tom

 

[rizzoa13]

Not having seen the extent of the rot or having felt the structure from above We can't really tell you how much to sister.

If it's structurally sound and you just need something to screw your deck boards to then by all means sister small blocks to it for nailers. Personally I'd go back at least a few feet to good sound material and lag bolt your blocks back there also.

I'd just rebuild the entire thing though because I hate bandaids especially st my own house.

 

[kevinculle]

Thanks for the advice and comments, but my way of thinking is that this thing has been on the house for 50+ years so I would say it was designed and built right.

The deck joists do run the same direction as the floor joists in the house which run the width of the house - 40'.  I've looked inside and outside and can't see how it is attached.

Thanks,
Tom

Tom,

Based on your description the only explanation that makes sense is that the joists in your deck are the floor joists in the house extended out through the wall, otherwise you would necessarily be seeing a long run (16' if properly constructed) inside the house where the deck joists were joined to the floor joists.  One aspect of proper engineering is to provide a means of future maintenance and repair...if my suspicion is correct that seems to be missing here.  A lot has changed in 50 years including building codes.  Do as you see fit but an elevated deck is not a wise place to take structural shortcuts.

 

[Bob D.]

The 2:1 cantilever rule for joists is correct and that makes this deck quite unusual; an 8' cantilevered deck using 2x8 joists (equivalent to a 16' span between supports) seems to be well beyond published joist span tables and possibly the structure was not properly engineered in the 1st place.  An easy fix would be to add outer supports, address rotting joists and end up with a more conventional structure.  If you want to keep the cantilevered structure I would strongly recommend consulting a structural engineer as there are real risks to you and your guests if this is not properly resolved.

I agree, and it's why I asked for the clarification earlier. Eight feet seems excessive (and unsafe) with no support.

 

[tvgordon]

I didn't include this in the original post as it was a repair question and not a deck design question, but the rim joist sets on two horizontal steel I-beams that travel the width of the house.  So the deck is attached to the house and rests on nearly 50' long steel beams.  The rim joist and where the joists attach to it seem sound.  The top of the joists that are exposed to sun and snow and ice and rain have some rot on the surface, but I haven't taken up the deck board to see how deep it goes.

And yes Rizzola, if I had the money now I would just rebuild it, but when I bought the house a few years ago I updated a lot of things so I waiting for the money to build back up before I do a major rebuild.

Tom

 

[rizzoa13]

I'm a little confused. If it's a cantilever deck then there isn't really a rim joist on the house side, the deck joists go back on through the house.

Is there blocking in between the joists at the house side or is there a one piece rim joist?

 

[Cheese]

I guess I'm curious how high this deck is above the ground. If it's only 4' or less above the ground, then why not just install some additional vertical supports at the 5'-6' mark. This means that the sistering joists can be shorter, which means lighter and there will be an additional bearing for them. Any visual issues with the additional vertical supports can be hidden with landscaping and plants, especially the climbing variety.

I guess I assumed that the deck joists actually were connected into the structure inside the building envelope. If they're just connected to a rim joist then that's a lot more scary issue...especially if they project out 8'.

 

[tvgordon]

Maybe I'm using the wrong term.  I was thinking the rim joist runs perpendicular to the joists.  This board, whatever it's called, is at the outer edge of the deck.

The deck is 7-8' off the ground.

Tom

 

[semenza]

I am just trying to visualize how the deck is actually attached to the house and stays up? It seriously can't just be bolted to the house with eight feet sticking out unsupported?  Is it actually cantilevered or something else?

Seth

 

[leakyroof]

I am just trying to visualize how the deck is actually attached to the house and stays up? It seriously can't just be bolted to the house with eight feet sticking out unsupported?  Is it actually cantilevered or something else?

Seth

  Can we NOT get any pictures of this deck?.  It's got all of us curious... [popcorn]

 

[tvgordon]

It really is cantilevered, but like I said earlier, there are two horizontal steel i-beams that run along the basement ceiling and extend out that support the board that the joists attach to.  The deck is around both sides and the back of the house and there are not any vertical posts supporting it.  It only extends out 8' along an 18' section behind the house, the rest of it is about 4' wide.  The deck is sturdy, I was just asking about a good way to repair some rot before I get around to rebuilding the whole thing.

Well I just spent over a half hour trying to upload a few photos and no luck.  I don't know if it's because I'm using a Mac or what, but I've never had any luck getting photos to post.

Tom

 

[Bob D.]

So you're saying that these two I-beams are cantilevered out under the 8 foot wide section of deck and the deck joists are supported by the beams?

 

[Cheese]

It really is cantilevered, but like I said earlier, there are two horizontal steel i-beams that run along the basement ceiling and extend out that support the board that the joists attach to.  The deck is around both sides and the back of the house and there are not any vertical posts supporting it.  It only extends out 8' along an 18' section behind the house, the rest of it is about 4' wide.  The deck is sturdy, I was just asking about a good way to repair some rot before I get around to rebuilding the whole thing.

Well I just spent over a half hour trying to upload a few photos and no luck.  I don't know if it's because I'm using a Mac or what, but I've never had any luck getting photos to post.

Ok, I missed the 2 horizontal I-beams part... [doh]...now this thing starts to make sense, unfortunately, now we really need to see some photos because this isn't the typical deck that the average Joe would be familiar with. Certainly I've never dinged around with one like this and I'm known for incorporating "hybrid building techniques".  [eek]  Important information would include the the width and thickness of top & bottom flanges and the height and thickness of the web.

Everything I post here is from a MAC or iPhone, so that's not the issue. Maybe you could e-mail the photos to [member=1619]SRSemenza[/member] and Seth could then post them?

 

[semenza]

It really is cantilevered, but like I said earlier, there are two horizontal steel i-beams that run along the basement ceiling and extend out that support the board that the joists attach to.  The deck is around both sides and the back of the house and there are not any vertical posts supporting it.  It only extends out 8' along an 18' section behind the house, the rest of it is about 4' wide.  The deck is sturdy, I was just asking about a good way to repair some rot before I get around to rebuilding the whole thing.

Well I just spent over a half hour trying to upload a few photos and no luck.  I don't know if it's because I'm using a Mac or what, but I've never had any luck getting photos to post.

Tom

I think the word horizontal was confusing me. I read about the beams but didn't get the direction they were running. Beams are perpendicular to the house wall  that the deck is built against?

Did you try the picture posting info I sent your way last week?  Sending you a message now.

Seth