Bath fan, recessed cans, new drywall, how to cut out holes

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Old 11-30-09, 10:41 AM
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Bath fan, recessed cans, new drywall, how to cut out holes

We took out old drywall in bathroom and put in recessed cans from Home Depot that have a seal to keep out humidity. We also have a Broan OXT series ventilation fan we also bought from Home Depot.

We watched a TOH video on how to install drywall on a ceiling with Tom Silva and he used a spiral scroll saw for cutting holes for the recessed cans. It was a good video but the problem we are having is that the fan and the lights have lips on the units so even if we go out and buy a spiral saw to cut it like the video shows it will only cut to the inside dimensions of the lights and fan. The lips on the fan and lights will prevent the units from pushing through the drywall and allowing the covers to attach properly to the units. The cans we bought were for new construction but they still have a small lip to them.

We had installed the fan two years prior with old drywall but the attic space is so narrow and we had a difficult time installing it and just ended up gerry rigging it knowing we will be replacing drywall. So trying to install them after putting up drywall is not good option. Plus we already installed them to the joists.

Since the cans have a smaller lip to them I can see where somehow we can widdle away where they will pass through the dry wall but the fan has wider lip and not as easy. If we do this then there will be significant gap and do we caulk this to prevent heat loss? Any suggestions as to how to widdle away without too much damage to housing? The fan lips even have holes in the lip to secure it to drywall. We picked this fan because it had the most features we needed. I don't think they make these fans with these options for new construction. I read on another posting that someone cut the lips off the fan housing and not sure how to go about that. It's too bad Broan hasn't addressed this yet.

Is the spiral scroll saw the best option to cut out any drywall holes? We have a dremel and I wondered if there is an attachment for Dremel that would work as well. We also have a router and wondered if there is an attachment that wouldn't rip up the can housing? Since we are slowly remodeling if spiral scroll saw is best option then would anyone recommend one brand over another and/or one model over another and why?
 
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Old 11-30-09, 02:27 PM
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Cut the drywall using the lip of the fan as a template. Your cover plate will cover over the lip and extend well onto your sheetrock. Can lights are best cut with hole saws the proper diameter and a drill. You can buy an adjustable sheetrock hole saw for less than $20.
 
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Old 11-30-09, 03:55 PM
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If you start your cuts on the inside until you reach the housing you can then pull the bit out and move it to the outside of the housings.

Be careful paying attention to which way you cut. One way will want to cut wildly while the other direction is much more controlled.

I use the latex low expansion foam to seal any gaps areound the fan housings and metal duct tape over any open slots.

The Roto-zip bit are the same size as the Dremel bits. You could try using your Dremel. You may want to practice on some scrap first.
 
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Old 12-01-09, 08:12 AM
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I think we thought that it had to be a more exact and tight fit than it has to be. From the sounds of it I think we can do this with the tools we already have and take our time cutting it. Tonight after work we should be able to get at least one piece up from the sounds of it. We appreciate your thoughtful responses.
 
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Old 12-01-09, 09:35 AM
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The electrical code requires that the gap around boxes be no more than 1/8". A saw blade width around your housings should be fine.
 
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Old 12-02-09, 10:11 AM
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I posted to another site and someone recommended that I could possibly use a crayon (ink pad sounds even better) on the lip of the recessed cans and fan and then lightly press the drywall on it to get an exact outline of where to cut. This sounded like a great idea and a good way to get a more exact cut for folks who don't do this a lot. Has anyone tried this or used something else?
 
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Old 12-02-09, 12:11 PM
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Yeah, crayons and lipstick make good markers. They are 1/2" wide and will smear, so if you want to use that for your line, OK, but I believe if you don't want to cut it with a Dremel type tool, you should take exact measurements to each corner, trace out your design and cut it with a knife or sheetrock keyhole saw.
 
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Old 12-02-09, 12:54 PM
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Here is a video on how to do it: YouTube - Center Mark IMO there is really no reason to buy their product because all you have to do is measure and mark it before you put the drywall up. They are even using a Dremmel in the video. Just remember when you put the drywall up keep your screws 18-24" away from the can or the drywall will just tear out. Not a huge deal but just more to patch.
 
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Old 12-03-09, 09:46 PM
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We did try ink then lipstick on the lips of recessed fan and can but it didn't work at all for the fan since the heat duct drops a little lower than the lips so the lipstick never did touch the drywall. The can did not in fact have a lip as my husband told me so there wasn't much of a surface to put lipstick on. It sort of made some marks but all in all it didn't work well for our situation. We decided to buy a Roto Zip and boy is that thing slick and made the job go so much smoother. We are doing a small bathroom with all sorts of issues so getting the dry wall in place is a bit of a circus act so avoiding the whole step of putting lipstick on the drywall surface and then taking it down again to cut out was a lot of extra work. Thanks to all who responded.
 
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