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-   -   Cutting through floor joists (http://www.diychatroom.com/f19/cutting-through-floor-joists-70637/)

chacha_m 05-06-2010 07:33 AM

Cutting through floor joists
 
Hi everyone,

I tried cutting through my floor joists last night and just couldn't get through them!! I was using a corded 1/2" drill with a 3" hole saw bit but I couldn't get any leverage because I'm working on the ceiling floor joist drilling out towards my exterior wall. Does anyone have and ideas of what else I can try. I did eventually get through one hole but it took almost 2 hours and my bit is very dull!! I have 5 more to get through and I need some advice.

Thanks,
Cha Cha

Scuba_Dave 05-06-2010 08:50 AM

How big is the floor joist & why a 3" hole ?
Muts be at least a 2x10 for a 3" hole

http://media.rd.com/dynamic/24/70/49...ts_001_sz2.jpg

fabrk8r 05-06-2010 09:16 AM

If the joist meets the criteria that Scuba_Dave provided then you can rent a "hole Hawg" from your local tool rental place.

http://i89.photobucket.com/albums/k2.../hole-hawg.jpg

The bit shown in the drill is sometimes called a "wood owl". This type of hole auger cuts through a 2X like butter.

chacha_m 05-06-2010 09:45 AM

The joist is a 2 X 6" that is why we are cutting a 3" hole. It is for a range hood. The duct work is supposed to be 6" but we can't cut a hole that big. I will contact my tool rental shop and see if I can rent one.

Thanks!

tpolk 05-06-2010 09:46 AM

be careful it will break a jaw or wrist if not held tightly

chacha_m 05-06-2010 09:53 AM

That's what was happening yesterday. The drill kept torquing and hands and faces kept getting in the way.

tpolk 05-06-2010 10:12 AM

this may be dumb question but you do have a pilot bit in hole saw yes?

chacha_m 05-06-2010 11:10 AM

yes, there is a pilot bit in the hole saw bit

Scuba_Dave 05-06-2010 11:12 AM

Quote:

Originally Posted by chacha_m (Post 438220)
The joist is a 2 X 6" that is why we are cutting a 3" hole. It is for a range hood. The duct work is supposed to be 6" but we can't cut a hole that big. I will contact my tool rental shop and see if I can rent one.

Thanks!

Cutting a 3" hole in a 2x6 joist (5.5") will virtually destroy the load carrying capacity of the joist
How many joists are you cutting ?
Is it a bedroom above, attic ?

chacha_m 05-06-2010 11:15 AM

it's a bedroom above. I'll be cutting through 2 joists plus the joist to the exterior wall (all double joists)

tpolk 05-06-2010 11:29 AM

no holes like that in 6" joist, floor will fail

chacha_m 05-06-2010 01:24 PM

even if I support it??

Willie T 05-06-2010 02:12 PM

CLICK HERE for some good joist reading with fun cartoons.

Snav 05-06-2010 02:41 PM

Quote:

Originally Posted by chacha_m (Post 438185)
Hi everyone,

I tried cutting through my floor joists last night and just couldn't get through them!! I was using a corded 1/2" drill with a 3" hole saw bit but I couldn't get any leverage because I'm working on the ceiling floor joist drilling out towards my exterior wall. Does anyone have and ideas of what else I can try. I did eventually get through one hole but it took almost 2 hours and my bit is very dull!! I have 5 more to get through and I need some advice.

Thanks,
Cha Cha

You have to rethink your approach to your work, you will only cause more problems to fix later if you drill through joists - no matter how else they're supported or braced.

A picture of your work area will be helpful. There's often a solution that you might not be able to come to on your own.

But from the sound of it your joists are undersized (a 2x6 can't hold much of a load and should never be used as a support joist for an above floor if it spans more than a few feet)
so - since you have access to your joists why don't you just install new full length joists of the proper size (depends on the span and load) and then you will have the means to install your pipe.

OR - if you don't want to or can't step up the size of your joists you might want to consider that you just can't go through the ceiling at all. Instead of going through the ceiling consider if it's possible to travel the pipe through the cabinet (either inside of it or above it in the empty cavity). This is a common and acceptable solution.

Scuba_Dave 05-06-2010 02:47 PM

Quote:

Originally Posted by chacha_m (Post 438311)
even if I support it??

Suport it with what ?
You would probably need steel plates & the fix would need an engineer to certify it is strong enough
What is the span on the joists ?
Cutting out 3" means you can almost guarantee the 2 joists will break


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