I am currently building my first deck and ran into a height issue with how tall I poured my footers. I needed to lose about 2.5″ in height between the frame and the decking, and I discovered that you can notch your joists and beams if following strict guidelines.
Now just a few facts on the build:
-I am currently located in Colorado and my city uses the 2015 IRC
-The deck is a 16’x20′ attached to a ledger on the house
-My footers are 12″, attached to which are 6″x6″ posts, which I have notched to attach my beams which are 2-2″x10″
-I am using pressure treated southern pine, with a beam span of about 6’10” and a joist span of about 8’2″
What I want to do is notch my beam where it crosses my post with a 1.5″ notch. This will need to be an actual width of 5.25″ and this is where the code loses me. I see in IRC 502.8.1 that you can notch the edge of a board to 1/4 its width (which I should be in the clear on) but I don’t see how wide this notch can be. The illustrations provided show a single beam span, but I am using 2 lengths of beam to make up the 20′ run.
I am fairly certain I will be good on my joist notching as this seems to be fairly common and the notch wont be more then 3″ wide.
Any ideas on whether this beam notching will be permissible?
Replies
Is there a reason why you can’t cut the post instead of the beam?
Notching joists is different from notching beams, so I’m not really sure what the rules are on that but you might need a different reference, if you can find one…
As I understand the diagram you provided only applies to joists.
The section of IRC that I pulled this from references the notching of beams and joists, so I assume its not different. Ive found a few other resources that confirm this detail but what I am trying to avoid is building the joist frame on top of these beams, only to have to tear them down and rebuild if there is some nuance in the code im unaware of.
Cutting the posts isnt an option due to the size of the posts. Any shorter and I will have trouble attaching them to the footer to post connector. I would also have the entire weight of the deck resting on about 1.5 inches of post which seems lik eit woul dbe all too easy for that post to crack.
If you don’t believe me maybe you will believe jlc:
https://www.jlconline.com/deck-builder/rules-for-drilling-and-notching-deck-framing_o
“Provisions for deck beam spans and performance have only recently been added to the 2015 IRC, but so far there is no guidance for making any modifications to them”
How much wood is below your beam is immaterial, as long as it’s solid.
I would consider direct beam to footing connection with a pt 2x4 shim below cut to whatever size you need. Like what they use in this article:
https://www.finehomebuilding.com/membership/pdf/9799/021249070.pdf?fhb_sid=djMtNDlmNTExMTYtOWQ4OS0xMWU3LWI0ZGUtMTIzZGNmYzhjMjVlfDE2NTYxMTcwNjk%3D&fhb_token=4b6febe1a2be1b251f8af6cd93a72cbf
can you set a taller beam directly on the footers?
You're allowed to notch the end of a beam up to 1/4 of its depth (not width). In your case, the depth of a 2x10 is 9.25 inches. For a 2-ply 2x10, the max notch is 2-5/16 in. deep (9.25/4). The length of the notch (not width) cannot be more that 1/3 of the depth of the member. So the max length of the notches in a 2x10 (in your case 2-ply) is 3-3/32 in. The problem you'll run into is easier to draw than explain, but I'll try. The spans are measured from one post to the next. So for any intermediate post, you'll be able to notch twice the length of the max notch length - 6-3/16 in. (2 x 3-3/32 in.). But over the end posts, the notch can only be 3-3/32 in. long. So if you want your beam to either end at the edge of the end posts or cantilever over them, you're out of luck. Bite the bullet and trim down your post height. It's going to be a heck of a lot easier than trying to cut 10 precise notches in your beams. Also, you didn't mention what the joist spans were from your center beam to your outer beam. If you've split them in half (two 8-ft. spans), your spans seem to be ok. If the center beam is closer to the house, your outer beam might be overspanned, in which case you would certainly not want to notch it.