Cantilevered Beam

[Glenn]

Not to mention CSST, Simpson strong may have something patent pending; this is may save your day in this instance; Deck Rail Post To Rim BoardFrancis

That is from FastenMaster by OMG, not Simpson.

It is a very good product.

 

[ICE]

"Cantilever" when applied to beams has a specific technical meaning including bearing conditions and equations to determine code compliance.

Another cantilever

 

[darcar]

Must use through bolts with nuts to secure guard post; lag and other screws are subject to withdrawal.Francis[/font]

How is a screw subject to withdraw? A straight shank nail I can see withraw issues but not a screw...

 

[Francis Vineyard]

How is a screw subject to withdraw? A straight shank nail I can see withraw issues but not a screw...

“The lag screw connection detail failed by withdrawal of the threaded portion from the band joist at an average ultimate load of 178 pounds.”

“For the bolted deck rail post assembly shown in Figure 2, the connections failed at an average load of 237 pounds - barely surpassing the code required design load with almost no safety factor for the service life of the assembly.”

STRUCTUREmag - Structural Engineering Magazine, Tradeshow: Tested Guardrail Post Connections for Residential Decks

Francis

 

[darcar]

“The lag screw connection detail failed by withdrawal of the threaded portion from the band joist at an average ultimate load of 178 pounds.”“For the bolted deck rail post assembly shown in Figure 2, the connections failed at an average load of 237 pounds - barely surpassing the code required design load with almost no safety factor for the service life of the assembly.”

STRUCTUREmag - Structural Engineering Magazine, Tradeshow: Tested Guardrail Post Connections for Residential Decks

Francis

I'm not the one building to meet minimum code but the arguement will be even though it "barely surpassed the code minimum", it still does meet minimum. I wish I could enforce my standards but cannot unless I'm paying for it

 

[facade3a]

I am new here. Can I ask;

3 story frame house. First story CMU wall. I want to cantilever 2nd & 3rd floor 4' making building width 32'. Back span 18' Conforming code is IRC which has table for cantilever roof & a wall, not roof and story. If I double up 2nd floor floor joists 2x12 every one of them, is that adequate to support roof load 3rd floor load and 2nd floor load?

 

[cda]

welcome welcome

sorry not an engineer so cannot answer your question, but stay tuned and you should get some answers.

Answer Might be that you need a strucural engineer to look at it.

 

[steveray]

It would be wise to contact a design professional as there are a lot more things to look at than the joist sizes....

 

[Francis Vineyard]

cda is correct in accordance with section R301.1.3

 

[Mr. Inspector]

Back to the deck. Don't you make them put blocking between the joists at the beam when there is a cantilever? See table R502.3.3(2)e

 

[Francis Vineyard]

Back to the deck. Don't you make them put blocking between the joists at the beam when there is a cantilever? See table R502.3.3(2)e

Yes, however the table is for balconies. For decks see 2015 IRC;

R507.5.1 Lateral restraint at supports. Joist ends and

bearing locations shall be provided with lateral restraint to

prevent rotation. Where lateral restraint is provided by

joist hangers or blocking between joists, their depth shall

equal not less than 60 percent of the joist depth. Where lateral

restraint is provided by rim joists, they shall be

secured to the end of each joist with a minimum of (3)10d

(3-inch x 0.128-inch) nails or (3)#10x3 inch (76 mm) long

wood screws.

OR (2009 IRC)

R502.7 Lateral restraint at supports. Joists shall be supported

laterally at the ends by full-depth solid blocking not less than 2

inches (51 mm) nominal in thickness; or by attachment to a

full-depth header, band or rim joist, or to an adjoining stud or shall

be otherwise provided with lateral support to prevent rotation.

 

[Mr. Inspector]

What's the difference between a deck and a exterior balcony?

 

[cda]

About ten feet In height ???

 

[Francis Vineyard]

Good question. In reference to the above sections balconies; the interior floor joist extend or cantilever beyond the exterior wall. Decks generally have the floor assemblies attached to the exterior wall if not free standing.

 

[JBI]

But isn't it the case that in construction we use the term cantilever for this situation?The below is from the 2010 CRC:

2.2. Floors shall not cantilever past the exterior

walls.

If I'm not mistaken they are referring to a floor overhanging the exterior wall. There's many more examples in the building codes where an overhanging situation is referred to as a cantilever or am I missing something?

The deck joists are cantilevered. The deck beam is overhanging.

 

[Francis Vineyard]

John that CRC section more than likely applies to seismic design category E.

Roofs overhangs are in the IRC. Additionally the term overhang is frequently used in the AWC Wood Deck Construction Guide.

For cantilever beams see IRC 2015 R507.6.

Suppose we all use these terms interchangeably as with beams, girders and headers.

Contradicting my earlier reply how can a balcony be self-supporting?

R311.5.1 Attachment. Exterior landings, decks, balconies,

stairs and similar facilities shall be positively

anchored to the primary structure to resist both vertical

and lateral forces or shall be designed to be self-supporting.