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Using 10 #10 screws to fasten rafter ties to rafter tails…

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Using 10 #10 screws to...

Using 10 #10 screws to fasten rafter ties to rafter tails which was previously specd by PE from JustAnswer. Due to the difficulty in installing these screws in this cramped location looking for alternative fastener in an lesser amount that will hold the rafter thrust load. Called customer service and they said I can request the same PE (***************) that worked on issue starting 10/6

Submitted: 9 months ago.Category: Structural Engineering
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Answered in 1 hour by:
10/19/2017
Structural Engineer: StructuralEng, Consultant replied 9 months ago
StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7,715
Experience: Structural Engineer
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Hello. I'll be happy to help you.

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Structural Engineer: StructuralEng, Consultant replied 9 months ago

It's getting very late here. I will get back to you in the morning.

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Customer reply replied 9 months ago
No problem.
Customer reply replied 9 months ago

Hi ******* Working on project. In lieu of 10 screws I'm using can 5/16 3/8 1/2 carriage bolts or lags be used instead being stronger I assume that less could be used which would make the install nuch quicker and easier. can you check the detail I sent you to see if the amount and size you determine I need would fit in that space on the 2x4 tie and what spacing would be required. Me and neighbor are dead tired just from installing those 10 screws at the rafter. this would be the topic I would be advice on this go around

Customer reply replied 9 months ago
FYI - LedgerLoc structural screws have to shear strength of 1,250 lbs tech says that they use 25% of that to determine the acceptable load carrying capacity in wood. However theie specs have spacing requirements that I do not meet in that small space maybe thay can still be used once you do youe calcs. screws r shank are1/4"
Structural Engineer: StructuralEng, Consultant replied 9 months ago
Let me check into a couple different products and get back to you. I may have to submit a premium service offer to sketch this up for you
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Customer reply replied 9 months ago

*********I have asked this a few times and got no response. Is the use of the carriage bolts or lags an option? I would think that something like a thru bolted connection such as a carriage or hex bolt would be strong enough and the only question would be is if the wood would fail in a 2x4 under the use of an reduced amount . It seems that you feel that these type fasteners are not suitable for what where trying to do here since you said you where going to look on the market for others that can be used..

Structural Engineer: StructuralEng, Consultant replied 9 months ago
I'm not saying the fasteners aren't adequate, what I'm saying is the value stated can't possibly be for a wood to wood connection. It's the strength of the steel. It can't possibly be for a wood to wood connection without knowing the angle to grain and side member thickness and main member thickness.
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Structural Engineer: StructuralEng, Consultant replied 9 months ago
One or two lags or through bolts concentrates too much load in one or two locations. It needs multiple smaller fasteners. I will submit a premium service offer to sketch out and study the layout and provide you with a layout that will work. Please attach a sketch to scale and at the proper angle and I will study the fastener layout
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Customer reply replied 9 months ago
Drawing that I sent to you was in scale 3"=1 ft. In regard to "angle" are you referring to the angle of the grain I the 2x4 tie. If that is the case that would impossible to give you that. I have 48 2x4 im dealing with here. All would be somewhat different.
Structural Engineer: StructuralEng, Consultant replied 9 months ago

Great. I will submit the offer to you now for me to study this. If you accept the offer, I will need until Sunday morning to get it to you (I have some personal commitments this weekend)

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Customer reply replied 9 months ago
Mark. If I accept you spec tasters that you choose have to be readily available and they they can't intrude into the rear angle ( wall side) of the of the tie. That portion 8.5" section is not accessible. I'll speak to my wife about the premium cost
Structural Engineer: StructuralEng, Consultant replied 9 months ago
That's fine. Please mark on your sketch in some way what portion of the overlap is not accessible.
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Customer reply replied 9 months ago
In looking at the sketch there are 2 dimensions one says 10" and the other says 8.5"witch the tie follows the the slope of the roof that 8.5" that is the part that you cannot reach.
Customer reply replied 8 months ago
Mark spoke to my neighbor who's helping me and we feel that unless we can get the fastener count down to 5 max standard type fasteners that we should just carry on what we"re doing. The extra expense and time frame getting expensive estructural fasteners would not justify the switch.Let me know if what you plan to propose falls within this limit so I can give you authorization to make the sketch.or not.
Structural Engineer: StructuralEng, Consultant replied 8 months ago
I can limit the fastener count to 5, but it won't be a standard wood screw. It might be some other type of screw, but should be easily found. I just won't know until I do the study
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Customer reply replied 8 months ago
Mark I totally understand your explanation on ultimate shear ratings of bolts and lags. and that that 1 or 2 fasteners put too much stress on the wood at one location.
After speaking with tech dept at SPAX, they explained that they call out the actual working load limit of there lags at 25% in wood of the tultimate shear in their specs. 1/4 lags have a ultimate rating of 770 lbs and a working rating of 190 lbs in a wood connection if the spacing is abided by.. This reduction of 25% takes into account things like grain direction, knots,etc. These lags are available at HD at only 25 cents ea. Other than the IMO excessive spacing (which you can determine can be adjusted) 5 can be used to restrain 900 lbs of force,. The proper placement though would have to be entered in the sketch for confirmation. This cost would put me at $2.50 per rafter pair.
Structural Engineer: StructuralEng, Consultant replied 8 months ago

I just looked into the product and the ESR. It is not nearly as simple as taking the allowable shear strength and using 25% of it for the capacity in wood. And it shouldn't be, the behavior is much more complex than that and is a function of many factors that can't be accounted for so simplistically. I will have all the information I need in the ESR to calculate the allowable loads in the wood based on your actual conditions.

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Customer reply replied 8 months ago
what is ESR
Structural Engineer: StructuralEng, Consultant replied 8 months ago
It's the service report that documents they're testing and all the requirements for the building code.
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Customer reply replied 8 months ago
I will be having an additional carpenter starting tomorrow. I will see how he makes out crawlling in that cramped space. if he has a very hard time Ill have you draw up the spec on the reduced amount of fasteners.
Structural Engineer: StructuralEng, Consultant replied 8 months ago

How did it look?

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Customer reply replied 8 months ago
We're going to continue with the screws like we've been doing
Structural Engineer: StructuralEng, Consultant replied 8 months ago

Great. Do you have any other questions for me on this topic?

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Customer reply replied 8 months ago
No
Structural Engineer: StructuralEng, Consultant replied 8 months ago

If you could rate my answer, I would appreciate it.

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Customer reply replied 8 months ago
I will when they send me email again asking for that
Customer reply replied 8 months ago
Hi Mark Im sorry I think I deleted the email that asked me to rate your answer. How can I do that without responding to an email prompting me to do that..
Also on a different subject, I had a follow up question on the correspondence we had last month regarding the spreading rafters where you spec'd the amount and spacing of the #10 screws I needed for the splices on the rafter ties I was using on a project I was doing. Could I get that or would I have to pay the $54 which I will
Structural Engineer: StructuralEng, Consultant replied 8 months ago

You should be able to do that here without that email. I can detail that out for you, but I will need to submit the premium service offer again. Just let me know if you want me to do that for you.

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Customer reply replied 8 months ago
Don't understand. Are saying u just have to offer me the premium service or I have to accept the premium service before I can rate your answer or get a follow up question on last months go around
Structural Engineer: StructuralEng, Consultant replied 8 months ago

I have to offer you the premium service for detailing that connection. A follow up question is no problem, but detailing the connection as previously discussed would require the premium service.

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Structural Engineer: StructuralEng, Consultant replied 8 months ago

Nevermind. I see it was already offered here.

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Customer reply replied 8 months ago
what can I do to rate. Your answer
Structural Engineer: StructuralEng, Consultant replied 8 months ago

I'm not sure what it looks like from your side, so I'm not certain.

Do you need the premium service or no?

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Customer reply replied 8 months ago
No we completed the work using the 10screws at the rafter connection as you instructed and didn't need to have an alternate plan drawn up
Structural Engineer: StructuralEng, Consultant replied 8 months ago

Got it. So yes, just rating the answer. Did you have any follow up questions?

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Customer reply replied 8 months ago
Hey Mark I a follow up question regarding the confirmation on the lap joint pattern that we used. However, I looked at emails on the the first go around we had last month and found the one that you confirmed was acceptable for the application ( 20 #10x3" screws 10 on each side of lap installed in 2 rows 1" in from edge and spaced 2" apart). I totally forgot about this exchange. As for the rating on your answer is the following acceptable. The experts answer was that given the limited space and the complexity involved an engineered drawing should be done on the fastener type and placement for the connection. I was quoted a premium service offer for this however We decided not to change the method we were using all along and opted not to have expert draw up the plan that would use a lesser amount of fasteners to handle the load involved. Overall was impressed with expert knowledge with dealing with my situation.
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