Structural Engineering

Ask Structural Engineering Questions and Get Expert Answers ASAP

Ask an Expert,
Get an Answer ASAP!

Structural Engineering

I'm wondering how to calculate roof purlin contribution to

Customer Question
Hi, I'm wondering how to...
Hi, I'm wondering how to calculate roof purlin contribution to beam load
JA: OK. Tell me a bit more about what's going on so we can help you best.
Customer: I want to remove a bearing wall and bury a beam in the ceiling to support the weight. Single story and purlins on the roof rafters mid-span transfer load to the bearing wall I want to remove. What fraction of roof weight should be attributed to the exterior bearing fall vs the interior (transmitted through purlin bracing)?
JA: Is there anything else the Structural Engineer should be aware of?
Customer: 20 foot span. Walls on either side are supporting purlins also and are ~12' away. I am not sure yet if joist are parallel or perpendicular to wall. But, perhaps I can get an answer on just the contribution of the load transferred to purlins to the interior wall. Say, if roof load is say 40 psf, should I count 20 psf as load through the purlin bracing (the rest going to the exterior walls that the rafters rest on)? If not, then how to think about it?
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Structural Engineer about your situation and then connect you two.
Submitted: 1 year ago.Category: Structural Engineering
Show More
Show Less
Ask Your Own Structural Engineering Question
Answered in 5 hours by:
6/21/2016
Structural Engineer: StructuralEng, Consultant replied 1 year ago
StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7,383
Experience: Structural Engineer
Verified

Hello.

Ask Your Own Structural Engineering Question
Structural Engineer: StructuralEng, Consultant replied 1 year ago

When you say purlins, do you mean beams supporting the rafters that are parallel to the ridge and between the ridge and eave?

Ask Your Own Structural Engineering Question
Customer reply replied 1 year ago
Exactly. There are angled brackets going from the purlins down to by bearing wall in question, and also to bearing walls 12' on either side.
Structural Engineer: StructuralEng, Consultant replied 1 year ago

Great. So with that in mind, what exactly is the question? The bulk of the roof load appears to be carried by these purlins.

Ask Your Own Structural Engineering Question
Customer reply replied 1 year ago
That is my question. What fraction of roof load should be considered transferred to the bearing walls through the purlin supports, versus transferred to the exterior walls that the rafters are sitting on? It is a gable roof in this area and the purlins are mid-span on the rafters on each side. What is accepted practice for sizing a beam to take up the purlin weight that was transferred to the wall to be removed? Or, is there another/better solution such as up-sizing the purlins to span more (24' vs 12').
Structural Engineer: StructuralEng, Consultant replied 1 year ago

Based on your description, 12.5% goes to each exterior wall (25% total) and 37.5% to each purlin (75% total).

Ask Your Own Structural Engineering Question
Customer reply replied 1 year ago
Thanks! What about the "beef up the purlin" question. As I said, I don't know yet if joists are parallel or perpendicular to the wall to be removed. But, assuming for the moment that they are parallel, it seems the only thing making it a bearing wall is the load transmitted through purlin bracing. In this case, would it be an acceptable solution beef up the (2x6) purlin in this area by sistering on additional beam to make it able to safely span 24' instead of 12' in between walls? If acceptable, what size and type beam might I be looking at (tell me if you need more info to specify). This would probably be easier that putting in a large beam above the wall area.Certainly, if the joists are perpendicular, I'd put a beam in the ceiling to support them as well as this purlin load. What size beam (double LVL I imagine) to support the 20' span?Side question: If beam in ceiling to support overlapping ceiling joists, are wood (say, 2x4) "droppers" screwed to the beam (with beam placed on top of joists) and joists with large structural screws acceptable, or do I need purpose-built joist hangers? It would be nice to use droppers if allowable since then I would not need to cut the ends off the overlapping joist ends in order to place them in joist hangers off the beam, and there seems to be ample clearance in the ceiling for the beam to go over the joists.Some additional info that might help: In my area, using 20 LL and 20 DL for roof, no snow. Ceiling load 10 LL and 5 DL (drywall and insulation only, no attic storage).
Structural Engineer: StructuralEng, Consultant replied 1 year ago

The joists are typically perpendicular to the ridge (parallel to the rafters). If they are parallel, then you are correct, but that would be atypical.

Ask Your Own Structural Engineering Question
Ask walkereng Your Own Question
walkereng
walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 2,618
2,618 Satisfied Customers
Experience: Over 30 years of Structural Engineering experience.

walkereng is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

walkereng

walkereng

Consultant

2,618 satisfied customers

Over 30 years of Structural Engineering experience.

vgdlpc

vgdlpc

Master's Degree

17 satisfied customers

Civil Engineer, Major in Structures and Foundations. Professional Engineer 11 years of experience.

StructuralEng

StructuralEng

Consultant

7,383 satisfied customers

Structural Engineer

Matt

Matt

Engineer

40 satisfied customers

Mechanical Engineering Hons degree, been working in automotive industry for the last 18 years - Engine development engineer

ibosley

ibosley

Master's Degree

88 satisfied customers

Mechanical Engineering

Ellen

Ellen

Consultant

109 satisfied customers

attorney and legal researcher

P. Simmons

P. Simmons

Attorney

138 satisfied customers

45 years old, retired Marine Officer, current attorney

< Previous | Next >

Related Structural Engineering Questions
What size beam do I need to span 23' to hold 10' floor
what size beam do I need to span 23' to hold 10' floor joists? I have limited access to the property so I need use 2x lumber to build the beams … read more
walkereng
walkereng
Consultant
2,618 satisfied customers
I have a about a 16 foot span from top of 8" thick concrete
I have a about a 16 foot span from top of 8" thick concrete wall to top of concrete wall under a floor. I am setting a 800 pound 'aga oven' (english cast iron water jacket oven) in the center of the s… read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
Question about applying 1/2" osb over perfectly good
Question about applying 1/2" osb over perfectly good exterior 4x8 sheets of 1977 smooth siding. Should I remove old and install new 1/2" osb to accept new 8" lap siding. Seems crazy to remove old if w… read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
I am building a garage that is 16 1/2' wide and 24' 10" deep
I am building a garage that is 16 1/2' wide and 24' 10" deep with a 3/12 pitch roof. I want to put a ridge beam in that would span the 16 1/2' and support the rafters. I need to know what size of beam… read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
I have and interior header I want to install, wall to wall
I have and interior header I want to install, wall to wall is 25', the header will be 19 feet, what size beam is safe ? … read more
walkereng
walkereng
Consultant
2,618 satisfied customers
I have a 4” x 4” I-beam to span a 38' space. There will be a
I have a 4” x 4” I-beam to span a 38' space. There will be a 4,000 lb total load hanging from the I-beam at four evenly spaced points. What size and how many posts would I need to support the I-beam? … read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
We would like to know how much weight we need to support
we would like to know how much weight we need to support with a new 8 ft beam in our two story home. We live in minnesota so we do need to plan for the weight of snow … read more
walkereng
walkereng
Consultant
2,618 satisfied customers
I am trying to figure out what size i beam to use for a
i am trying to figure out what size i beam to use for a staircase , can u help? … read more
walkereng
walkereng
Consultant
2,618 satisfied customers
How do i check a steel pile for shear strength failure? How
how do i check a steel pile for shear strength failure? How do i calculate the maximum shear ratio? What is the allowable ratio?… read more
walkereng
walkereng
Consultant
2,618 satisfied customers
I have a single family home and have to remove 12 ft of load
I have a single family home and have to remove 12 ft of load bearing wall on outside of home and trying to find out what size of header is needed … read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
I am restoring an old home near Mena Arkansas. It's a 2
I am restoring an old home near Mena Arkansas. It's a 2 story with low ceilings due to duct work added for central A/C. I would like to remove a 22 ft span of 2nd floor and create an open space betwee… read more
walkereng
walkereng
Consultant
2,618 satisfied customers
The slab for my basement was poured a couple weeks ago.
Hello! The slab for my basement was poured a couple weeks ago. Yesterday I notice a crack (vertical) at the edge of the slab. Only vertically. There is no cracking on the slab surface. See pics and pl… read more
walkereng
walkereng
Consultant
2,618 satisfied customers
I'm attempting to remove a wall in my bathroom and I found a
I'm attempting to remove a wall in my bathroom and I found a 4x4 stud in one corner. I'm trying to determine if it is load bearing or not. … read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
Are you allowed to cut studs on the outside and install pvc
Are you allowed to cut studs on the outside and install pvc plumbing?? I feel cutting 2 inches into a stud is wrong?… read more
walkereng
walkereng
Consultant
2,618 satisfied customers
I plan on removing a portion of a load bearing wall in my
Hi. I plan on removing a portion of a load bearing wall in my house and replacing it with steel i-beam. I need assistance in determining the beam size required and support post placement. The room spa… read more
walkereng
walkereng
Consultant
2,618 satisfied customers
Calculation for a glue Lam Beam and a house I have four
Calculation for a glue Lam Beam and a house I have four locations one I need is a 16 foot span supporting were the two static Joyce come together in the middle of the house nothing above it but attic … read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
I am trying to find out how much weight (PSI) - load bearing
I am trying to find out how much weight (PSI) - load bearing that a 4'x4'x1/2" piece of plywood would hold. We use 4"x4" sheets of 3/4" normally to cover excavated holes up to 3' diameter. Someone sug… read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
Size of a glue lam beam span 14" lenght of room 23" feet.
size of a glue lam beam span 14" lenght of room 23" feet. the beam will be supporting a 2nd floor room plus roof? … read more
StructuralEng
StructuralEng
Consultant
7,383 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x