Need help/suggestions for Deck framing problem.

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Kerrylib

Well-Known Member
looks good. For that low of deck did it even need a permit? I believe around here (Denver, co) most cities don't bother unless it is high enough to need railings. Now you have the permit and proof it was signed off, so it is a definite +.

As for the high footing. Could you have taken a circ saw w/ diamond blade to it and chopped it down so you could rest the beam right on top? Messy job, but good for whoever didn't plan out the finished height of the piece.

Wuzzat?

Well-Known Member
Total Load Deflection = .1213" - L/495
Live Load Deflection = .0866" - L/693

"A deck would be a floor, so it is limited to L/360 deflection under a 40 PSF live load (from Table R301.5)."
L is the span in inches and L/360 means dividing the span by 360 to get the midspan deflection, so for L = 10' = 120" you are allowed up to 120/360 = 1/3".

That's a pretty stiff deck.

nealtw

Contractor retired
Very strange, I doubt that 4x4 passes for a beam anywhere, anytime something like this comes up you should be sent to an engineer, who may well come to all of these calculations and give it a pass.
But there should be a big discussion of the 4x4 used as normally a 4x4 is not graded to be used as a beam, a 2 or better may not be strong enough. An engineer would have a few stippulations like no heart wood, direction of the grain and size and location of knots. As an engineer is responsible for what he passes for 30 years they are really carefull on what they say will do the job, I'm surprized this guy didn't just call for another post midspan.

Wuzzat?

Well-Known Member
Closer caisson/post spacing allows for a weaker drop beam. It's all inter-related.

I would have tested this by having a person of any weight (a concentrated load) stand perfectly still in several places and then use formulas to convert the deflections to PSF (a distributed load).

http://www.engineeringtoolbox.com/beam-stress-deflection-d_1312.html

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bud16415

Fixer Upper
Staff member
Admin
Moderator
Just because the beam had to be reduced to 4 inches doesn&#8217;t mean you have to go with a 4 inch beam. I would have stuck with the ratied beam and just reduced the end (birds mouth) to fit to the high support point. Then I would have platted that end to return the strength.

nealtw

Contractor retired
Just because the beam had to be reduced to 4 inches doesnt mean you have to go with a 4 inch beam. I would have stuck with the ratied beam and just reduced the end (birds mouth) to fit to the high support point. Then I would have platted that end to return the strength.

Engineers, don't like a cut like that in a beam, the cut out is the weekest spot and makes the beam less than not equal to the smaller size.. They will not even allow and 1/8 notch to fit a beam, they would sooner you take 1/8" off the whole beam.

slownsteady

Well-Known Member
Just a thought, but couldn't you set a 4"x4" post on each of the low tubes and then build your deck at that height? That is, of course, assuming that the highest caisson is at the right level to begin with. (good question: is the highest one too high????)
And then you could just abandon the old caissons and start brand new......(make the deck a little wider)

Sorry, i didn't realize i was so late to the conversation. I got to the end of page 1 and had a thought without looking further.

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bud16415

Fixer Upper
Staff member
Admin
Moderator
Engineers, don't like a cut like that in a beam, the cut out is the weekest spot and makes the beam less than not equal to the smaller size.. They will not even allow and 1/8 notch to fit a beam, they would sooner you take 1/8" off the whole beam.

I can understand why an engineer wouldnt want a beam trimmed like that because the sharp corner is a stress riser. Most carpenters wouldnt do anything to help relieve that high stress point in fact most of the time they would make the cuts with a skill saw and cut past the corner due to the radius of the blade.

Old houses around here circa 1900 or older all the floor joists were made that way and set in mortised pockets so that the beam and joist all came flush. The way they did it before joist hangers. Many of these old houses have splits in the joists starting at the sharp corner.

The way to make the cut I would think is with a reciprocating saw and leave no corner run the cut out on an arc and taper down to the full width then add a ¾ thick plywood plate on both sides cut similarly glued and screwed.

But you are correct if the inspector, engineer, etc. wont approve it no matter how strong you made it there would be no reason to do it.

MrMiz

Junior Member
looks good. For that low of deck did it even need a permit? I believe around here (Denver, co) most cities don't bother unless it is high enough to need railings. Now you have the permit and proof it was signed off, so it is a definite +.

As for the high footing. Could you have taken a circ saw w/ diamond blade to it and chopped it down so you could rest the beam right on top? Messy job, but good for whoever didn't plan out the finished height of the piece.

According to the city you always need a permit. When I talked to the inspector he said they really don't even look at anything under 30". Which I translate as they just want the permit for some quick \$\$ and to raise your taxes. Increased "valuation" of your home.

The diamond blade was actually going to be our next "solution" if the inspector didn't pass the 4X4. I do wonder if you cut down the top of the caison then doesn't that change the depth for frost? I thought the 4x4 was a long shot but like I said they don't care about anything under 30", and it makes sense... if the 4x4 breaks the drop is going to about 1" or so.

Wuzzat?

Well-Known Member
You could run a 3.5" x 3.5" square steel strap around the beam end to reduce the chance it would split lengthwise. A 1/16" thk x 1" wide strap may be strong enough and minimum strap length would be 4 x 3.5".

BridgeMan

Well-Known Member
And having no safety railing around the perimeter, it would be wise to not let Granny (or any aging friend/visitor/relative) out there very long, unattended. It's an accident waiting to happen.

I'm speaking from experience. My 80-year-old mother stepped off my back patio (9" above the lawn), fell onto the grass and broke her hip. She was never the same after that, even with the stainless steel hardware they used to fix the fracture.

Osteoporosis?