Joist Overhang Question

941 Views 9 Replies 2 Participants Last post by Nealtw, May 19, 2020

Brandonc2q88

Discussion Starter · May 19, 2020

I have a question regarding joist overhangs.

I'm building a freestanding cantilever design deck next to my pool. The posts are about 2' high and sit on top of 12" diameter concrete piers with anchoring hardware, etc.

There is about 2'-6" of joist overhang from the last supporting beam to the edge of pool deck. The total length of joist is about 10', with the span in between the two beams at 6'-6".

Our building office references the 2012 IRC, and according to that I shouldn't be able to do more than 1/4 of the 6'-6" span (i.e., max joist overhang should be just over 1'-6").

BUT.... I just called my inspector, and he said it's actually all good, and that...

A) Rather than a 4:1 span to overhang ratio it's actually 3:1 and even 2:1 is acceptable if there is no roofing structure overhead bearing down on the deck.

B) The way the joist span is calculated in these equations is the TOTAL length of the joist, not the length of the joist in between the two beams.

I'm wondering if I should just roll with it and build as is, or possibly throw one more post down in there to create a short diagonal beam that attached to the main beam with an angled joist hanger and some diagonal bracing?

Thoughts?

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Nealtw

· #2 · May 19, 2020

Brandonc2q88 said:
I have a question regarding joist overhangs.

I'm building a freestanding cantilever design deck next to my pool. The posts are about 2' high and sit on top of 12" diameter concrete piers with anchoring hardware, etc.

There is about 2'-6" of joist overhang from the last supporting beam to the edge of pool deck. The total length of joist is about 10', with the span in between the two beams at 6'-6".

Our building office references the 2012 IRC, and according to that I shouldn't be able to do more than 1/4 of the 6'-6" span (i.e., max joist overhang should be just over 1'-6").

BUT.... I just called my inspector, and he said it's actually all good, and that...

A) Rather than a 4:1 span to overhang ratio it's actually 3:1 and even 2:1 is acceptable if there is no roofing structure overhead bearing down on the deck.

B) The way the joist span is calculated in these equations is the TOTAL length of the joist, not the length of the joist in between the two beams.

I'm wondering if I should just roll with it and build as is, or possibly throw one more post down in there to create a short diagonal beam that attached to the main beam with an angled joist hanger and some diagonal bracing?

Thoughts?

The way they right that L4 is confusing if you divide 6'6" by 3, you get 2'2" add that to 6'6" the to get 8 ft 8" from the end of the joist to the far beam and the overhang is 1/4 of that.

Can you play with the position of the beams and posts on the piers to gain a few inches.

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Brandonc2q88

Discussion Starter · #3 · May 19, 2020

Nealtw said:
The way they right that L4 is confusing if you divide 6'6" by 3, you get 2'2" add that to 6'6" the to get 8 ft 8" from the end of the joist to the far beam and the overhang is 1/4 of that.

Can you play with the position of the beams and posts on the piers to gain a few inches.

No I really can't the piers are already set with anchor bolts in place.

It's actually 3' overhang on the far end, so I'm about 6" over the 1:3 ratio beam to beam.

I may just run a short diagonal beam similar to the other side of pool to add additional support under the overhang. Would superficially connect it to the main beams with some angled cuts and an adjustable framing angle.

That or I may just run another lighter duty beam (2 2x10's) parallel that is freestanding and connected to the other posts maybe with some diagonal bracing.

See images.

Thoughts?

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Nealtw

· #4 · May 19, 2020

Brandonc2q88 said:
No I really can't the piers are already set with anchor bolts in place.

It's actually 3' overhang on the far end, so I'm about 6" over the 1:3 ratio beam to beam.

I may just run a short diagonal beam similar to the other side of pool to add additional support under the overhang. Would superficially connect it to the main beams with some angled cuts and an adjustable framing angle.

That or I may just run another lighter duty beam (2 2x10's) parallel that is freestanding and connected to the other posts maybe with some diagonal bracing.

See images.

Thoughts?

3 ft would be pushing your luck, either of the drawing would work,
I have cut out post holders and drilled in new ones.

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Brandonc2q88

Discussion Starter · #5 · May 19, 2020

Nealtw said:
3 ft would be pushing your luck, either of the drawing would work,
I have cut out post holders and drilled in new ones.

Assuming I do the extra beam to support the overhang running parallel with the main beam and right up against the pool wall, the footer may fall right up against the footer for the corner post (maybe 6"-12" of soil horizontally separating the two concrete piers.

Is this an issue structurally in any way that they'd be so close to each other. Does the weight automatically just distribute over the two posts almost equally after doing that, or does the rigging compromise the integrity of the overall structure somehow?

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Nealtw

· #6 · May 19, 2020

Brandonc2q88 said:
Assuming I do the extra beam to support the overhang running parallel with the main beam and right up against the pool wall, the footer may fall right up against the footer for the corner post (maybe 6"-12" of soil horizontally separating the two concrete piers.

Is this an issue structurally in any way that they'd be so close to each other. Does the weight automatically just distribute over the two posts almost equally after doing that, or does the rigging compromise the integrity of the overall structure somehow?

That wouldn't be problem, but you could just move the beam to the new location. No? Yes?

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Brandonc2q88

Discussion Starter · #7 · May 19, 2020

Nealtw said:
That wouldn't be problem, but you could just move the beam to the new location. No? Yes?

No way, I dug the holes by hand, mixed concrete by hand, etc.

The piers are already in 2 days now and backfilled (by hand too LOL)

So I'd rather save myself the effort and just spend $50-$75 and just add two additional posts and a parallel beam that's 2' over closer to the pool so I'm not cantilevered more than 1' at any point for peace of mind (as long as it doesn't screw up the structural integrity somehow)

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Nealtw

· #8 · May 19, 2020

Brandonc2q88 said:
No way, I dug the holes by hand, mixed concrete by hand, etc.

The piers are already in 2 days now and backfilled (by hand too LOL)

So I'd rather save myself the effort and just spend $50-$75 and just add two additional posts and a parallel beam that's 2' over closer to the pool so I'm not cantilevered more than 1' at any point for peace of mind (as long as it doesn't screw up the structural integrity somehow)

Where you have it marked 10'6" , how far would it be to go all the way back to the beam under your porch ?

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Brandonc2q88

Discussion Starter · #9 · May 19, 2020

Nealtw said:
Where you have it marked 10'6" , how far would it be to go all the way back to the beam under your porch ?

It would be about another 2 feet.

BUT those beams run perpendicular to these beams. The two decks are separate with about 1/2 inch space in between the two.

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Nealtw

· #10 · May 19, 2020

Brandonc2q88 said:
It would be about another 2 feet.

BUT those beams run perpendicular to these beams. The two decks are separate with about 1/2 inch space in between the two.

So something like this?

an angled post coming from the piers to hold the extra beam

With another member on the end going back to the back beam to stop the lateral movement

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