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Header beam for a masonry penetration
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Source：Internet Author：Unknow Pubdate：2008-04-15
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jacpe (Structural)
26 Apr 07 17:19
I'm putting an addition on the back of a house that was built with exterior cmu walls. The new addition calls for the existing rear french door to be removed and the opening increased to 8 ft. Is there any reason that an LVL header cannot be used to support the masonry wall above? This wall effectively becomes an interior bearing wall with no possibility of moisture content becoming an issue with the LVL.
concretemasonry (Structural)
26 Apr 07 20:50
You cannot support the masonry with wood.
jacpe (Structural)
27 Apr 07 7:45
Thanks for the response. Please provide the reason that this is so. In this case where the wall has existed for 40 years and will become an interior wall, I am trying to find out why it should be treated as anything other than a dead load. There is no moisture condition. Does dry mortar or block interact with an LVL?
字串7
MiketheEngineer (Structural)
27 Apr 07 10:32
In some coded areas - they are worried about fire. The LVL burns up and down comes the masonry.
Where I am, they have allowed this condition if a lintel is attached to an LVL even though the wood beam is actaully carrying the lintel and most of the load.
In a truly hot fire - metal beams will often fail before heavy thick wood beams which simply char.
You might try an assembly using a steel plate on top of the LVL and see if that flies??
If not - you are probably stuck with angles under each side of the masonry.
Good Luck
concretemasonry (Structural)
27 Apr 07 10:52
If it is just an 8' span on a residence, just stay with compatible materials and eliminate all the dissimilar properties, creep problems, moisture possiblities and confusion. 字串4
Use a 16" deep masonry lintel (16" deep lintel block or a lower bond beam and the next course filled at the same time) to support the wall above. To build the lintel, use temporary shoring. Build the wall above. You will have enough height in the second floor wall to achieve arch action, which reduces loads on the lintel significantly. Make sure you have a bond beam for bearing and continuity at the top of the second floor wall.
If you are extremely concerned, you could go to a 24" deep lintel, but that could be counter-productive and a little messy depending on the details.
It is difficult to beat the continuity of construction and similar materials. Dissimilar materials lead to too many difficult situations as the building ages.
scottiesei (Structural)
27 Apr 07 12:54
I often encoutner this. Try checking the strength of an unfilled masonry header with the applied loads. Typically I get by with them cutting out the existing header, but leaving the tie beam and mortaring in a new unfilled precast.
字串5
csd72 (Structural)
27 Apr 07 15:42
Under sustained loads the timber will creep eventually causing cracking in the wall.
How would you support the ends of a LVL anyway?
Easiest is to use an angle each side of the wall.
ironmon (Structural)
21 May 07 13:15
Building Code IBC 2003 Section 2034.12
"Wood members shall not be used to permanently support the dead load of any masonry or concrete"
8 foot is a long span for angles. Although it can be done, just we're at the upper limit for angle.
The best way to do this in a multi-wythe wall is with (2)
W8 beams (4 inch flange)W8x10 or 13. Insert in one face at a time. In other words, create opening in outer wythe, insert beam, then repeat in inner wythe. This is a good detail for exsiting walls, where temp shoring cannot be used or is impractical.
字串9
csd72 (Structural)
21 May 07 23:10
ironmon,
If your going to do this, put 5/16" plate needles throught the wall in the mortar bed just above the new lintel. Support these with a shore at each end.
With the wall above supported, install the new lintels directly under and cut off the end of the needles once you remove the shoring. Weld remainder of needles to top of beams for restraint.
regards
Csd
JKW05 (Structural)
24 May 07 13:31
2006 IRC, R606.10: "Masonry over openings shall be supported by steel lintels, reinforced concrete or masonry lintels or masonry arches . . ."
2006 IRC, R703.7.3: "Veneer above openings shall be supported on lintels of noncombustible materials . . ."
CJPW (Structural)
14 Jun 07 14:15
字串3
I agree with csd72. the timber will creep over time leading the cracking through the mortar. Also there is the problem of stiffness (timber cf masonry). The easiest solution would be a prestressed lintel/or RC which you should be able to buy of the shelf of a builders merchant.
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