Author Topic: New Beam for cottage  (Read 6639 times)

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Offline mandorpheus

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New Beam for cottage
« on: October 27, 2014, 09:58 PM »
Hello all,

So we have a cottage that is essentially 24 feet x 30 feet.  It's an old rafter roof system(not trusses) with 2 gable ends. 

We originally had 2 main walls spreading across the 30 foot span with separation for halls/entrances.  At one point we had  torn down one of the walls and the general contractor had put in 3 2x6 over a 16 foot span.  At first this wasn't that bad - but the ceiling originally had fiberboard(stuff used back in the 50s or so).  Later on, drywall was put on - overtop of the fiberboard.  So obviously some additional weight that wasn't necessary.

This eventually led to that 3 2x6 beam over that 16 foot span to sag(clearly wasn't a large enough beam should've been at least 3 2x8).  There was another beam added which was perhaps a 10 foot span again used 3 2x6, but this beam never did sag.

What we're looking to do is have an LVL beam installed to span the 30 feet.  Ideally we don't want any jack posts.  Does anyone have an idea if this is a possibility?  And/or what size of LVL Beam would be required for this?  The purpose of the beam would essentially be to hold up the ceiling across the cottage.

We've obviously torn down the drywall and fiberboard - but will only install drywall afterwards.

Any advice on specs, etc. would be much appreciated.

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Offline tjbnwi

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Re: New Beam for cottage
« Reply #1 on: October 27, 2014, 10:02 PM »
Roof pitch and snow load please?

Tom

Offline wow

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Re: New Beam for cottage
« Reply #2 on: October 27, 2014, 10:13 PM »
First, [welcome] to the FOG!

There are a multitude of resources for LVL applications, but any lumber yard or home center should be able to help you size it appropriately. Your local building codes may actually specify the product you will need to install.


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Offline mandorpheus

  • Posts: 6
Re: New Beam for cottage
« Reply #3 on: October 27, 2014, 10:29 PM »
roof pitch is 5-12.  Rafters are 24" on center

snow load I found online is the following(based on 2005 numbers): 
Snow Load kPa, 1/50
Ss = 2.6
Sr = 0.4

Offline tjbnwi

  • Posts: 5497
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Re: New Beam for cottage
« Reply #4 on: October 27, 2014, 11:18 PM »
How about in pounds per square foot. I'm metric challenged. When I do a conversion I get 0.42 pounds per square foot.

Tom

Offline mandorpheus

  • Posts: 6
Re: New Beam for cottage
« Reply #5 on: October 27, 2014, 11:32 PM »
It's all good.

Found 52.2 lbs psf

Offline Holzhacker

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Re: New Beam for cottage
« Reply #6 on: October 28, 2014, 08:52 AM »
You can do 30' with an LVL but its going to be big. A few thoughts...
- LVL manufacturers have span table PDF's for their different styles and sizes; go on their website, look up the table PDF, run through the combinations to find which one works for you; there are usually different options for height, thickness and type for a particular span
- that long of a beam is going to be pretty tall, make sure you pick a beam that still provides sufficient ceiling / walk through height
- it'll be heavy, you'll need mechanical help getting it into place; i.e. a crane, hydraulic hoists, jacks, etc
- you'll need to verify that your current end posts and footings can handle the load; putting that much load on 100 year old footings or 3" crap metal posts isn't going to cut it
"The Code is not a ceiling to reach but a floor to work up from"

Offline mandorpheus

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Re: New Beam for cottage
« Reply #7 on: October 28, 2014, 07:30 PM »
Roof pitch and snow load please?

Tom

Did you get my details Tom?

Offline tjbnwi

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Re: New Beam for cottage
« Reply #8 on: October 28, 2014, 09:06 PM »
You have 390 square feet of tributary load.

390x53=20,670 pounds
390x2.3=    897 pounds
Load        21567 pounds

21567/30=718.9 pounds per lineal foot the ridge has to support.

Looks like a 6-3/4"x19-1/2" Glulam.

You must be certain the ridge load is carried to bearing.

A local supplier should be able to verify what you need. They have software from the manufacture to check this.

The job will be very high on the difficulty scale. A crane is a must.

Tom


Offline mandorpheus

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Re: New Beam for cottage
« Reply #9 on: February 04, 2015, 12:08 PM »
Thanks for the info Tom.

Now was this for a ridge beam(board)?  Perhaps I wasn't as specific as required.

Essentially to recap it's a 24x30 building.  We essentially want to remove all load bearing walls and substitute it with a big LVL beam.  The load bearing walls are essentially holding up the ceiling joists.(See orange beam in image)

Now - there may be some roof/snow load on this - but I just want to confirm this type of beam would require to be the size you proposed.  At one point a general contractor removed one partition of the wall and replaced it with 3 2x6 over a 14-16 foot span.  Over time this eventually sagged.  Clearly wasn't big enough to hold the weight of the ceiling in addition to whatever else it may be holding.  From what I can see the rafters clearly go to the outer walls and don't see what other weight would be on the beam.

So if I wanted the full 30 foot span are your calculations still accurate?

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Thanks,

Offline mandorpheus

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Re: New Beam for cottage
« Reply #10 on: February 04, 2015, 12:10 PM »
sorry.  picture didn't attach properly.


Offline G3Trim

  • Posts: 48
Re: New Beam for cottage
« Reply #11 on: February 04, 2015, 01:06 PM »
You should spend a few bucks and have a engineer take a look at what your wanting to do. Ask him about putting the beam in the attic and hanging the ceiling joist with joist hangers. instead of under the joist so you can have a flat ceiling. I have seen it done before.

Offline wow

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Re: New Beam for cottage
« Reply #12 on: February 04, 2015, 01:16 PM »
If the rafters are designed and built correctly that orange beam is totally unnecessary.

All of the roof weight transfers down the side walls, while the base of the rafters prevents the walls from spreading. You only need to certify the design of the rafters for proper load rating, fastening, etc. With the right materials you should be good with that design, WITHOUT any beam.

But, as suggested before,  get a lumber yard or truss company to run the their program on it for you. They'll do it for free. If you can't find someone to do it for you you might need to hire a structural engineer, but that's a lot of $$$ an I doubt you'd need to resort to that.
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Offline Caly

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Re: New Beam for cottage
« Reply #13 on: February 04, 2015, 02:51 PM »
Have you considered "flitching"

Offline AzjaST

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Re: New Beam for cottage
« Reply #14 on: February 04, 2015, 06:42 PM »
Unless there will be heavy load on the attic floor, for this application beam is not necessary. Just sistering floor joists with 2x12 or 2x14 should be enough.

Offline wow

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Re: New Beam for cottage
« Reply #15 on: February 04, 2015, 06:46 PM »
Unless there will be heavy load on the attic floor, for this application beam is not necessary. Just sistering floor joists with 2x12 or 2x14 should be enough.

AzjaST, [welcome] to the FOG!

When you have time, be sure to start a new thread and tell us a little about yourself and your shop. We'd love to learn more about you and what you do.
Trying to be one of the most helpful members on the FOG.

Offline T. Ernsberger

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Re: New Beam for cottage
« Reply #16 on: February 04, 2015, 06:59 PM »
Definitely call an engineer!   

Offline duburban

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Re: New Beam for cottage
« Reply #17 on: February 04, 2015, 10:10 PM »
Unless there will be heavy load on the attic floor, for this application beam is not necessary. Just sistering floor joists with 2x12 or 2x14 should be enough.

Where do you get 2x14s?
helper: i used a festool "circular saw" to do something simple and it made it really hard

me: exactly, it makes simple cuts complicated and complicated cuts simple

Offline wow

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Re: New Beam for cottage
« Reply #18 on: February 04, 2015, 10:36 PM »
Unless there will be heavy load on the attic floor, for this application beam is not necessary. Just sistering floor joists with 2x12 or 2x14 should be enough.

Where do you get 2x14s?

Ask for Microlams (brand name, but kind of like 'Klenex') or LVL's - Laminated Veneered Lumber. They are available in sizes up to 5" x 26" or larger and lengths up to 52 feet.
« Last Edit: February 05, 2015, 01:42 AM by wow »
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Offline Dave Askew

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Re: New Beam for cottage
« Reply #19 on: February 05, 2015, 01:40 AM »
If you go into your local lumberyard, they will call Weyerhauser, or whomever there prefferred distributor is, and they will run the calculations on the spot and email/fax over the requirements.

They will give you all the options based on the specs you provide...single...doubles...triples and so fourth. When weyerhauser sends me a spec sheet, it's from there engineering department, and it's good for permits/approvals.

Dave

Offline AzjaST

  • Posts: 2
Re: New Beam for cottage
« Reply #20 on: February 05, 2015, 04:30 PM »
Unless there will be heavy load on the attic floor, for this application beam is not necessary. Just sistering floor joists with 2x12 or 2x14 should be enough.

Where do you get 2x14s?
Span tables  [big grin]
But, seriously,  you can sister existing 2x6 or 2x8 with 2x10 or 12 with partial overlap to get 2x14. Or even better, convert each existing set of rafters and joist to truss just by adding king post and two struts. Anything spanning 30' will be monstrous; if 2 posts every 10' are possible than single 9 1/4 LVL will do but make sure these posts have way to transfer loads to the foundation.