Cutting through floor joists

stubits · 05-06-2010, 03:18 PM

Also, but not nearly as serious as the joist notching, if your exhaust needs a 6" duct, a 3" duct isn't going to work correctly at all. It's going to be loud and no way will it pull the air you want. So, even if the collective body can come up with a way to run a 3" duct, you're still off.

I think it might be time to rethink this. What other options are available?

chacha_m · 05-06-2010, 03:42 PM

These are pics of the area I am working in

Scuba_Dave · 05-06-2010, 03:55 PM

Even worse, those look like they are 24" OC
That means by cutting (2) you are compromising the support over a 6' area
After your cuts there won't be anything left for support over a 6' wide area

drtbk4ever · 05-06-2010, 04:03 PM

Would it be possible to run it along the joists to an outside wall, like back over your head?

chacha_m · 05-06-2010, 04:07 PM

it's not because there was a back porch added on so the roof in the back is lower than the roof in the kitchen.

kindrox · 05-06-2010, 05:05 PM

I think you are looking at going throught the roof with a vent hole then. What you are doing with those beams looks like big trouble. I would also think a custom welded set of steel brackets, bolted to each beam, would do.

Like maybe a 40 inch long, 3/8" thick steel brackets exactly the height of the beams, with say two 4 inch holes punched out right next to each other in the middle of the bracket (two 4 inch holes will move about as much air as one 6 inch hole), with the brackets bolted to each beam with 6 bolts.

I am not an engineer but I'd be pretty comfortable standing under that. And around here you could get each bracket for about 100 bucks.

RoyalAcresRod · 05-06-2010, 06:34 PM

chacha: Please reconsider what you are doing...with your current plans you are seriously degrading the ability of your joists to do what they were designed to do, as well as completely ignoring the ducting instructions.

There is a reason your instructions say 6" duct...and you ignore them at your peril. You came here for advice, so please consider:

I'm assuming there will be cabinets in this area...is there some reason your cannot run the necessary 6" duct horizontally on top of the cabinets, and then build a soffit to the ceiling to conceal the pipe? That is very common solution.

Once you go through the wall, there will be a number of available solutions, including going up through the roof as was suggested earlier.

Too, your ducting instructions will have comments on the maximum length on the duct length, and how much each 45 or 90 turn counts as length.

These instructions are not printed just to fill paper....it is necessary for you to follow them!

There are many people here, and most much smarter than I, who will help you through this. With enough pictures, drawings, etc., a solution here will be found!

boman47k · 05-06-2010, 07:54 PM

2x6 ceiling joists?? Are you sure? Is this a very old house?

Anyway, pay attention to what is being said about the 1/3 reg. A 3" is not leaving much meat in the joist. Pratically none, relatively speaking, imo.

I amnoo engineer, but I am somewhat of a diy'er in most situations. But, I research just about anything if there is any doubt. I have been around rental property and houses long enough to pretty well know when I might need to know more than I do.

Kind of hard to get a clear picture of what yopu are dealing with. It sounds like you might could hang the pipe from the joists and enclose the proper size pipe and proper clearance between the pipe and combustibles within a soffit along the ceiling if need be. Just build a frame and cover it with drywall. Then through the attic and maybe vent it through the outside wall, if allowable, between the any structural members, if you do not want to go through the roof.
If it calls for 6" pipe, use 6" pipe.

Find out how many el's or 90's are allowed for the pipe within relative distances.You might want to check with someone to make sure this hood is the hood you need for this application considering the distance that may be involved for the fan motor to properly exhaust.

Just some thoughts on the project.

<*(((>< · 05-06-2010, 09:35 PM

Looks like you need to build yourself a soffit above your future cabinets, and run the 6" vent that the hood calls for.

Jim F · 05-06-2010, 10:30 PM

Chacha, what you are attempting to do borders on insane! You were wise to come here to get advice. Please follow the advice the experts and even the novices are trying to give you. Did you read Willie T's link? It will tell you all you need. What you need is to build a soffit underneath the joists you are attempting to hack through and above the cabinets to accommodate your vent as others have suggested. Otherwize, I feel sorry for whoever buys that house after you.

chacha_m · 05-10-2010, 11:08 AM

Just to let everyone know I didn't cut through them. Thanks for the advice!

HooKooDooKu · 05-10-2010, 02:18 PM

Quote:

Originally Posted by chacha_m

I did eventually get through one hole but it took almost 2 hours and my bit is very dull!

You now need to go back and fix this mistake. At this point, you might as well consider the joist cut-in-two and you need must reinforce it at the hole. I would get a 2x6 that's about 2' long and nail it to the existing joist centered over the hole. Even better would be an extra 2x6 on each side of the damaged joist.