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-   -   double top plate and LVL (http://www.diychatroom.com/f19/double-top-plate-lvl-140159/)

itsnotrequired 04-13-2012 08:19 AM

double top plate and LVL
 
1 Attachment(s)
sort of hijacked another thread so i'll ask this here as a new one.

see attached photo. i am looking to 'open up' the staircase into the basement by removing the door on the right (and associated header) as well as the wall along the stairs to the left, from the stringer to the joists. replace with an LVL header and appropriate column supports in either end. already had the lumber yard size the beams and two 14"x1.75", 2.0E will do the trick, 14' long.

so my question relates to the double top plate in the area where the LVL will go. can i cut it out, such that the joists rest directly on the LVL (and providing additional studs at the ends of the LVL to reinforce the remaining double top plate)? i'd like the 3" of additional headroom if i can get it.

Daniel Holzman 04-13-2012 08:25 AM

Assuming the LVL was sized to be adequate without the double top plate, you can remove the double top plate. Ask the lumber yard for the computations (if you don't already have them) so you can verify that they did not rely on the strength of the double top plate to augment their LVL selection. You probably need to submit the computations when you pull your permit anyway.

itsnotrequired 04-13-2012 09:12 AM

Quote:

Originally Posted by Daniel Holzman (Post 898003)
Assuming the LVL was sized to be adequate without the double top plate, you can remove the double top plate. Ask the lumber yard for the computations (if you don't already have them) so you can verify that they did not rely on the strength of the double top plate to augment their LVL selection. You probably need to submit the computations when you pull your permit anyway.

yep, i have the calcs. they originally came back and said two 11 7/8" LVLs would do it but they were maxed out. seemed like a recipe for bouncy floors. i had them re-run the calcs with double 14" and it was much less deflection.

not sure if they ran the calcs assuming the double top plate. good catch, i'll follow up.

i asked about having to submit calcs when i pulled the permit and the inspector said no. got the permit yesterday and didn't need them. still, i wasn't going to put this thing in without having someone more qualified than me size it!

Daniel Holzman 04-13-2012 09:18 AM

You should be able to easily determine if the calcs relied on the double top plate for additional strength, calcs are normally presented with assumptions written on the sheets, even if the formulas are complex and intimidating. If you cannot determine whether the top plates were includes (they most likely were not), just ask the lumber yard to verify.

cortell 04-13-2012 09:39 AM

My opinion: this is a no-brainer. I would remove the double top plate without hesitation.

Here's a little test you can do:
1. Lay two thick books of similar thickness on your basement floor 14' apart.
2. Grab two 14' 2x4's and fasten them together with clamps at their ends and in the middle (or screws/nails if you don't have clamps)
3. Lay the simulated double-top plate across the books.
4. Slightly start applying pressure with your hand near the middle of the run.
If the lumber starts bowing (which I'm sure it will), you have your answer. The double top plate's addition to the design strength of the LVL is negligible.

Excuse me while I get technical for a second. Some might object to this analysis and say: hey, what you've proved is that 2x4 lumber in that orientation has a low modulus of elasticity ("is very flexible", in layman's terms). You have not proved it has a low Fb (fiber stress in bending). In other words, if instead of books you put the plates on supports 6' off the ground, perhaps you could have a 500lb man walk across it without it snapping. Well, that's very true. I haven't proved that double top plate has a low Fb. But in this case, it's being combined with an LVL. I strongly suspect the LVL would suffer catastrophic shear failure before the double-top plates when bowed to that extreme. So, in effect, the Fb of the 2x4 in that orientation is also negligible.

All this said: I am not a mechanical or civil engineer. I just try to think like one :-). I'm simply telling you that in my mind, there's a near zero chance the lumber yard took into account a double top plate. If you have any doubts, though, do as Daniel said and check with them.

itsnotrequired 04-13-2012 09:40 AM

Quote:

Originally Posted by Daniel Holzman (Post 898026)
You should be able to easily determine if the calcs relied on the double top plate for additional strength, calcs are normally presented with assumptions written on the sheets, even if the formulas are complex and intimidating. If you cannot determine whether the top plates were includes (they most likely were not), just ask the lumber yard to verify.

almost positive they are not included but i have asked the lumber yard to confirm. thanks for the help!

in general, it seems like the double top plate would be used with LVL during initial construction, to help keep the wall straight or to tip up walls framed on the floor. seems like once the building is finished, the top plates could be removed like i am describing without impacting the remaining wall integrity/'straightness'. is my understanding correct?

psilva8 04-13-2012 09:41 AM

Out of curiosity, what will you be using for columns and did the lumber yard detail the footings if required?

cortell 04-13-2012 09:48 AM

Quote:

Originally Posted by itsnotrequired (Post 898041)
in general, it seems like the double top plate would be used with LVL during initial construction, to help keep the wall straight or to tip up walls framed on the floor. seems like once the building is finished, the top plates could be removed like i am describing without impacting the remaining wall integrity/'straightness'. is my understanding correct?

You will have to frame a temporary load bearing wall (maybe two) to remove that wall. The existing double top plates will have no role once those temporary walls are up. Unless, of course you're planning on offsetting the beam (installing it next to the existing wall)

itsnotrequired 04-13-2012 09:53 AM

Quote:

Originally Posted by psilva8 (Post 898042)
Out of curiosity, what will you be using for columns and did the lumber yard detail the footings if required?

calcs indicate two 2x4 stud on each end would be acceptable but i plan on using three, just for some extra security. this is the main bearing wall which runs the axis of the house (ranch home, no second floor). the area above the bearing wall on the second floor in this area doesn't have a wall on it (just a railing, staircase opens up into the living room). underneath this wall is a 16" wide by 8" deep footing running the length of the wall with a 4" slab over the top of it. i'm thinking point loads won't be a problem at the column supports.

or maybe it is a concern?

itsnotrequired 04-13-2012 09:54 AM

Quote:

Originally Posted by cortell (Post 898046)
You will have to frame a temporary load bearing wall (maybe two) to remove that wall. The existing double top plates will have no role once those temporary walls are up. Unless, of course you're planning on offsetting the beam (installing it next to the existing wall)

absolutely need a temp wall until the LVL is in, already in the plans!

cortell 04-13-2012 10:02 AM

It would definitely be a concern for me. You can't assume 8" of concrete is sufficient. I would without a doubt install oversized footers for each column.

Honestly, none of this should really be done without it being engineered. If you want to sleep well at night, spend some $ and hire an engineer. If you insist of saving that money, at least consider pouring yourself footers. I would do a 24"x24"X12", reinforced with #4 rebar 12" OC (make sure you keep the rebar 3" from the bottom of the footer)

itsnotrequired 04-13-2012 10:14 AM

Quote:

Originally Posted by cortell (Post 898052)
It would definitely be a concern for me. You can't assume 8" of concrete is sufficient. I would without a doubt install oversized footers for each beam.

Honestly, none of this should really be done without it being engineered. If you want to sleep well at night, spend some $ and hire an engineer. If you insist of saving that money, at least consider pouring yourself footers. I would do a 24"x24"X12", reinforced with #4 rebar 12" OC (make sure you keep the rebar 3" from the bottom of the footer)

this seems like an awfully large footer for a column supporting floor load only in a one story home. i could see this more for a two story house with a bearing wall all the way up to the room which carries roof load, snow load, floor load, etc.

cortell 04-13-2012 10:16 AM

Quote:

Originally Posted by itsnotrequired (Post 898059)
this seems like an awfully large footer for a column supporting floor load only in a one story home. i could see this more for a two story house with a bearing wall all the way up to the room which carries roof load, snow load, floor load, etc.

I absolutely agree with you. And if a licensed engineer said that, I'd say to him "let's go with whatever you suggest." However, if I'm bypassing an engineer, I'm going to over-engineer it so I can sleep well at night.

itsnotrequired 04-13-2012 10:26 AM

Quote:

Originally Posted by cortell (Post 898062)
I absolutely agree with you. And if a licensed engineer said that, I'd say to him "let's go with whatever you suggest." However, if I'm bypassing an engineer, I'm going to over-engineer it so I can sleep well at night.

i appreciate the concern. i thought about the column point load and the footing seems large enough but i'm going to bounce it off a couple engineer friends i have, just to get their opinion.

cortell 04-13-2012 10:41 AM

Quote:

Originally Posted by itsnotrequired (Post 898068)
i appreciate the concern. i thought about the column point load and the footing seems large enough but i'm going to bounce it off a couple engineer friends i have, just to get their opinion.

Believe me, if I had auto mechanic friends, I wouldn't bring my car to a shop either.

It sounds to me like you're thinking this through fairly well and not winging it. I predict you'll be quite successful with this project.


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