Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Carpentry

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 10-07-2009, 08:48 AM   #1
Newbie
 
Join Date: Oct 2009
Posts: 1
Rewards Points: 10
Question

How much load weight can a 4x4x14 redwood beam bear


I have an old house with a second floor with 3x3x14 rough cut redwood as the floor joists. I attached to them 4x4x14 redwood and put on top tongue and grove sturdy floor 3/4 inch. So combined, I have basically a 7x7x14 floor joist. My son wants to put a 90 gallon fish tank in his upstairs bedroom. It would lie on a single beam, maybe 2 (i cannot tell as floor is covered) running length wise on the beam. As water weighs 8.3 lbs per gallon, I estimate the load to be around 800 lbs US. Will that support the load?

lawdealer is offline   Reply With Quote
Old 10-07-2009, 09:23 AM   #2
Member
 
Join Date: Sep 2009
Location: Louisville
Posts: 455
Rewards Points: 250
Default

How much load weight can a 4x4x14 redwood beam bear


somewhere in my notes from structures i have the formulas for figuring that out. if i can find them tonight i can drop them in here for you, unless someone else knows it off the top of their head.

in theory however a Wx14 beam should be fine as the fishtank is a distributed load over your floor supports which are (in theory) spaced at 16" O.C. max. if your tank is 48" wide it spans 4 beams and your 800 lb load is divided by 4 and then is factored by the distribution. i am however not an engineer and its been 5 or more years since i took structures.

http://www.google.com/search?hl=en&s...&aq=f&oq=&aqi=
http://www.google.com/search?q=beam+...ient=firefox-a

those links have some beam load calculators. the formulas are correct but i dont remember which ones to use


Last edited by cellophane; 10-07-2009 at 09:28 AM.
cellophane is offline   Reply With Quote
Old 10-08-2009, 07:07 AM   #3
Man of many hats
 
wrangler's Avatar
 
Join Date: Oct 2008
Location: Florida Panhandle
Posts: 507
Rewards Points: 272
Default

How much load weight can a 4x4x14 redwood beam bear


Either I am misunderstanding your post, or your math is in error.
A 3x3 atop a 4x4 would at best give you a 3x7 since an inch of the 4x4 is not supporting anything, and depending on how they are attached to each other, I'm not sure that it even has that much lateral strength. An architect/engineer could better answer your question, but I'm sure they would need more info as well.
JMTCW
__________________
Man of many hats
wrangler is offline   Reply With Quote
Old 10-08-2009, 08:04 AM   #4
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000
Default

How much load weight can a 4x4x14 redwood beam bear


Usually recommendation is that larger fish tanks sit perpindicular to the joists & on an outside load bearing wall
thus spreading the load out
I have a 125 tank & I installed it directly over a beam in the basement
Scuba_Dave is offline   Reply With Quote
Old 10-09-2009, 07:31 AM   #5
Member
 
Join Date: Aug 2009
Posts: 133
Rewards Points: 75
Default

How much load weight can a 4x4x14 redwood beam bear


The joint between the 3 x 3 and the 4 x 4 does not lie in the center of the composite beam. All loads placed on this combined member will result in a shear force parallel along this joint. The only thing resisting the shear force is the quantity and thickness of the nail/screws or whatever is holding the composite beam together.

The limiting factor may not be strength of the wood.
MI-Roger is offline   Reply With Quote
Old 10-09-2009, 07:39 AM   #6
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000
Default

How much load weight can a 4x4x14 redwood beam bear


Quote:
Originally Posted by cellophane View Post
as the fishtank is a distributed load over your floor supports which are (in theory) spaced at 16" O.C. max. if your tank is 48" wide it spans 4 beams and your 800 lb load is divided by 4 and then is factored by the distribution. i am however not an engineer and its been 5 or more years since i took structures.
Except he stated the tank will run parallel to the joist & thus only sit on one joist - maybe 2
Scuba_Dave is offline   Reply With Quote
Old 10-09-2009, 10:00 AM   #7
Civil Engineer
 
Join Date: Mar 2009
Location: Boston
Posts: 4,252
Rewards Points: 2,082
Default

How much load weight can a 4x4x14 redwood beam bear


I could not tell from the OP whether the 4x4x14 was attached to the bottom or the side of the 3x3x14 beam. If attached to the bottom, the post regarding the need for proper shear connection between the two beams is spot on. If attached to the side, the connection is not as important. The moment of intertia of the composite section is completely different if the beam was attached to the side versus the bottom.

I also was not clear whether all of the joists were added on to in the same manner, or possibly only the one that is going to support the fish tank. Since the tank is apparently aligned along the axis of one of the joists, it may lie entirely on one joist, in which case it would have to be treated as effectively a point load. If it is a point load, the critical factor is the distance from the support ends, along with the weight. Once we know the method of construction of the beam, and the location of the tank, we can compute the bending stress and estimate the factor of safety against failure.

Daniel Holzman is offline   Reply With Quote
Reply

Tags
4x4, aquarium, redwood, support, weight


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
OSB Stronger than Plywood? Weathermaker01 Flooring 15 12-22-2012 09:06 AM
Tranferring load to basement beam and lally column cooperwd Building & Construction 3 08-17-2009 10:14 AM
Crawl Space Beam and Joist Support Questions Fire4Effect Building & Construction 5 06-28-2009 01:07 PM
Beam Load Ron Building & Construction 5 09-17-2006 06:28 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.