Thread: Girder/Beam on center 1/3 of column

I have this crazy notion that beams and girders have to rest on the center 1/3 of a column or post. Didn't find what I was looking when rummaging through the IRC.

Can anyone give me any pointers to source that backs up my foggy memory?

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3 inches on masonry.

R502.6 Bearing.

The ends of each joist, beam or girder shall
have not less than 1.5 inches (38 mm) of bearing on wood or
metal and not less than 3 inches (76 mm) on masonry or concrete
except where supported on a 1-inch-by-4-inch (25.4 mm
by 102 mm) ribbon strip and nailed to the adjacent stud or by
the use of approved joist hangers.

Your not going to find anything about eccentric loads in the IRC, but the vertical load action line should fall in the middle third of the column or pier to keep the stresses compressive, outside the middle third tensile stresses develop. Think tiddly winks, when you press down hard enough one side, the other side pops up.
You may be able to make R501.2 from the IRC work

There is 3 inches bearing on the masonry. Not the concern.

I understand the tiddley winks anology. I understand why it is a bad idea. I am just trying to find a definitive source that says you must place the beam centered over the suppport column.

If this is for a residential home inspection, just tell them it's a bad idea. Depending on the state, quoting code can get you in trouble.

Originally Posted by Troy Eskew

If this is for a residential home inspection, just tell them it's a bad idea. Depending on the state, quoting code can get you in trouble.

Thanks Troy. NC has some very specific rules regarding code quoting in reports. I don't quote code in my reports. I want to use the code as a means to backup my report. If the builder pushes back, I want to be able to refer him to a specific code reference and then ask him why it does not apply. I want to be prepared.

In this particular case, the columns are supporting a wood deck. The deck uses gravity to connect the deck to the masonry columns. Next time there is a party on the deck, I don't want the beam sliding off the column.

Builders will use the lack of code to push back and refuse to repair or replace. I would prefer to have a code reference in my back pocket to encourage the builder to rectify the substandard deck construction.

Gotcha.

R502.9 Fastening.

Floor framing shall be nailed in accordance
with TableR602.3(1).Where posts and beam or girder construction
is used to support floor framing, positive connections shall
be provided to ensure against uplift and lateral displacement.

It's a stretch but.........

R502.2 Design and construction.

Floors shall be designed
and constructed in accordance with the provisions of this chapter,
Figure R502.2 and Sections R319 and R320 or in accordance
with AF&PA/NDS.


Figure R502.2 shows the beams and girders being centered on their supporting piers.

while they are centering up the beam and tieing it to the column have them put some pressure treated wood under the beam as well

Do you have an overall picture of the deck?

Originally Posted by Bruce Ramsey

The deck uses gravity to connect the deck to the masonry columns.

How is it going to resist uplift in straight wind storm conditons (thunderstorm, microburst, blizzard, tornado, hurricane, etc.)?

Originally Posted by brian schmitt

while they are centering up the beam and tieing it to the column have them put some pressure treated wood under the beam as well

In this particular case, the columns are supporting a wood deck.

Brian, I would think that all of the framing is PT.

Originally Posted by Wayne Carlisle

It's a stretch but.........

R502.2 Design and construction.

Floors shall be designed

and constructed in accordance with the provisions of this chapter,

Figure R502.2 and Sections R319 and R320 or in accordance

with AF&PA/NDS.

Figure R502.2 shows the beams and girders being centered on their supporting piers.

I believe this makes a very good point, and if the builder disagrees, ask him to show you where the code says the beam can hang over the pier. (Yes I know that it is only the bond timber hanging over the pier, but I was trying to make a point.)

Try these: (underlining and bold are mine)
- R403.1 General. All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, wood foundations, or other approved structural systems which shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill.

The loading on the footing is not uniform when the load above is not located over the center of the footing, meaning that the load under the right side (in the case of the photo) of the footing will have a greatly increased load in pounds per square foot while the load on the left side of the footing will have a greatly reduced load, resulting in the compression of the soil under the right side and the possibility that the compressed soil will be pushed back under the left side, uplifting the left side.

Ever walked along a stepping stone walk on a soggy yard? Walk along the edges of the stepping stones and that edge will sink while the other edge rises. Happens every time.

I was going to add a couple of more references, but the above should do it.

Yes, the deck structure should be mechanically attached to the support columns. Tthe entire deck is made of pressure treated lumber. Thank you all the helpful ways in which the deck could be better. While certainly an interesting game, I am most interested in a specific reference that says loads must be in the middle third of a column.

I have included some additional pictures so you can continue to find fault with a multitude of other items.

I have included some additional pictures so you can continue to find fault with a multitude of other items.

I'm assuming since you posted the pictures that it is OK to ask about them. My only question would be, why is there siding under the porch? Shouldn't that be brick for the foundation curtain wall?

3.5.5.3 Eccentric loads on short columns & piers
Manual of Structural Design & Engineering Solutions

Originally Posted by chris mcintyre

I'm assuming since you posted the pictures that it is OK to ask about them. My only question would be, why is there siding under the porch? Shouldn't that be brick for the foundation curtain wall?

Everyone seemed to be having fun finding faults so I provided the additional pictures.

That is not a curtain wall, it is the foundation wall. CMU with brick veneer up to a point. Then the rest is platform framed covered by vinyl siding like the rest of the house.

Originally Posted by John Goad

3.5.5.3 Eccentric loads on short columns & piers
Manual of Structural Design & Engineering Solutions

And "3.5.5.3 Eccentric loads on short columns & piers" says ...

It is meaningless to post a section without posting what it says.

It says what I first posted, without the tiddly winks analogy.

Bruce....what you're thinking of doesn't apply to your specific condition.

Looking back, the old 1997 NC Building Code (based on CABO Vol VII) and subsequent 2002 NC Building Code (based on 2000 IRC) had the provision you are looking for in Footnote #3 of Table 403.1a:

"Centers of piers shall bear in the middle 1/3 of the footings, and girders shall bear in the middle 1/3 of the piers, except exterior girders. Footings shall be full thickness over the entire area of the footing."

But starting with the 2006 NC Residential Code, the same footnote changed to:
"Centers of piers shall bear in the middle 1/3 of the footings. Girders must have full bearing on piers. Footings shall be full thickness over the entire area of the footing."

Dave

Dave,

Excellent. I have both the 2002 and 2006 NC Building code books. Your references do back up my spotty memory.

Sometimes we inspect houses and things we have let go before become an issue. This is one of those times. Girders not resting in the center 1/3 was one of those issues that has come due. Thank you for the reference.