How JustAnswer Works:

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

Ask walkereng Your Own Question

walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 2590
Experience:  Over 30 years of Structural Engineering experience.
61772417
Type Your Structural Engineering Question Here...
walkereng is online now
A new question is answered every 9 seconds

I am an architect, and I have a residential renovation

Customer Question

Good Morning. I am an architect, and I have a residential renovation project being planned for a one story ranch in Westchester, NY. The main block of the house is going to be one large open space at 16' wide x 33' long. The exterior walls are 2x4, and the ceiling joists are 2x6. The roof rafters are also 2x6, and the roof angle is approx. 26 degrees. There is only one interior wall, but it runs parallel to the structure, and it is coming down.
The ceiling is 8', but the client really wants a higher ceiling. I suggested doing a raised section of the ceiling, using carrier beams and posts, but the framer suggested another idea that I need help evaluating. He wants to take out all of the ceiling joists, and then sister the roof rafters with LVL's. Then he would put in collar ties at some height like 9.5, or 10', which would also serve as the new ceiing joists. Could this work? Thanks, Lisa
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  walkereng replied 1 year ago.

I can help

Expert:  walkereng replied 1 year ago.

Do you have any plans you could share with me?

Expert:  walkereng replied 1 year ago.

Or rough sketches with the proposed configuration, could work.

Customer: replied 1 year ago.
Sorry - I had a client call. I will send you rough sketches - hang on.
Customer: replied 1 year ago.
Hi - the sketch of the section shows my initial idea. Basically, the framer wants to eliminate the soffit, and structural beams, and strengthen the roof rafters and use collar ties - this would be for the full length of the house -
Expert:  walkereng replied 1 year ago.

It could possibly be done. There are a couple of limits that need to be followed. I am attaching the 2012 IRC Code Section that covers Braced Rafters and Raised Rafters.

1. Your proposed sloped ceiling would need to act as purlin bracing and meet the 45 degree minimum requirement.

2. Your raised ceiling joists would be limited to being raised 1/3 of the HR value shown in my attachment.

Expert:  walkereng replied 1 year ago.

Let me know if you have any questions

Expert:  walkereng replied 1 year ago.

Of course, your added beams that will be accepting the purlin brace loads would have to be sized accordingly.

Customer: replied 1 year ago.
Thanks - but, the sketch shows what I was proposing. I was specifically asking about the framer's suggestion of eliminating the soffit, and carriage beams from my sketch - and just adding raised ceiling rafters that would be attached directly to the roof rafters. He was suggesting strengthening the roof rafters by sistering them - The sloped section of the finish ceiling would follow the line of the rafters above the plate. Is that scenario clear?
Expert:  walkereng replied 1 year ago.

Sorry, I was looking at your sketch as the proposed.

That can work as long as the roof rafters are sized accordingly and you do not raise your ceiling joists more than the 1/3 of the HR value shown in my attachment.

Expert:  walkereng replied 1 year ago.

If you feel you have received a satisfactory answer to your question, click the Rating button that is appropriate. Experts are credited for each appropriately Rated answer they provide. If you have additional questions, please let me know. Thanks

Customer: replied 1 year ago.
OK Thanks. But how would I size the roof rafters? The existing are to remain - they are 2x6's @ 24 - framer suggested adding 2x6 LVL's - he was going to sister them - I have no idea how to determine this - ie: if we add 2x6 LVL's then, how many- ie: sister to only one side or both. And, how often? ie: at each rafter or only every other??
Expert:  walkereng replied 1 year ago.

I can size them for you. I have a few questions:

1. What is the horizontal distance between the ridge board and wall the roof rafters will rest on (span of rafter)?

2. What city and sate do you live in for possible snow load consideration?

3. What type of roofing is on the house?

Customer: replied 1 year ago.
The span is 8' - the ridge is about 4' higher than the plate - it is a low slope roof. The house is in Chappaqua, NY - Westchester County, and the roofing is typical asphalt roofing/
Expert:  walkereng replied 1 year ago.

I’d like to point out that a Professional Engineer’s standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for planning purposes only (general sizing and budgeting) and is based on the information provided by you. All loading cases considered are for vertical loads only, no lateral analysis has been completed. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.

You can use conventional lumber 2x6's to sister to the existing 2x6's. This will give you double 2x6's spaced at 24" o.c.

I would add the additional 2x6 rafters to one side of the existing 2x6 rafters and then move the ceiling joists up the other side of the existing 2x6 rafter.

Since your "HR" value is 48", you are limited to 48"/3, or 16" to move your ceiling joists up above the wall top plate.

Customer: replied 1 year ago.
Thanks so much - I'll review this and the relevant code/ etc. Sincerely, Lisa
Expert:  walkereng replied 1 year ago.

If you feel you have received a satisfactory answer to your question, click the Rating button that is appropriate. Experts are credited for each appropriately Rated answer they provide. If you have additional questions, please let me know. Thanks

Expert:  walkereng replied 1 year ago.

If you could rate my answer, that would be great. Thanks

Related Structural Engineering Questions