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walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 2598
Experience:  Over 30 years of Structural Engineering experience.
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I have an existing deck that I would like to expand,

Customer Question

hi,
I have an existing deck that I would like to expand, the main longitudinal bearer beams are 3x2"x6" cedar beams joined together spanning approximately 11'. The beams currently supportan 8' wide deck (hence 4' supported by the beams and the other half suported by the ledger on the house wall). I would like to extend the deck by 6', therefore would be adding another 3' of load to the existing beams (the other 3' will be taken by a new bearer beam that I will install). Could the existing 3x2x6 take the additional load? Joist spacing is 16"
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  walkereng replied 1 year ago.
Before we get started 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.
So you want to know if your triple 2x6 Cedar beam that spans 11' can carry a 7' wide tributary width?
Customer: replied 1 year ago.
yes please. the deck is for residential use only
Expert:  walkereng replied 1 year ago.
Your triple 2x6 Cedar beam can not support the increased load width.
In fact, the existing condition is over stressed by 80% right now.
I used a Live Load of 40 psf and a Dead Load of 10 psf.
Customer: replied 1 year ago.
OK - thanks. strange about the overstressed condition, the current deck was build in 1976 and shows no signs of sagging or deflection.
Expert:  walkereng replied 1 year ago.
The reason why you have most likely not seen any problems is that your deck has most likely never actually been subjected to the Code Design Load.
Your current configuration beam capacity is right around a Live Load of 20 psf and a Dead Load of 5 psf.
If you feel you have received a satisfactory answer to your question, click the Rating button that is appropriate. Experts are credited for each adequately Rated answer they provide. If you have additional questions, please let me know. Thanks
Expert:  walkereng replied 1 year ago.
Let me know if you have any more questions
Expert:  walkereng replied 1 year ago.
I am still here to help if you need it.

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