Cutting a Return Air floor Vent

We just changed our flooring from carpet to bamboo & the metal floor vent does not fit as well now, mostly because it goes further into the floor than before & the people that originally put in that ductwork did not cut the hole correctly. Anyway I am looking at the possibility of making a cover out of wood. First thing is I am not sure it will be strong enough. I came up with this first test design & am 3d printing it at 1/4 scale to see how it looks. I may not cut it on the CNC, but just use a 1" forstner bit for the 133 holes. I have the holes spaced 1/2" apart. By my area calculations these holes allow 34% of airflow relative to current metal opening. The opening is 14x24 & overall dimensions of the grill are 16x26. For the wood, I was looking at maybe using the thicker stair treads & glue 2 of them to get the 16" width. I did that before on a table & it worked well. So, I really only have 2 concerns, is it strong enough to stand on & does it allow enough air flow? I could also use smaller holes and more of them & that might get me more air flow, but of course is more to drill. I attached an image and STL file of my 1st version & it is nothing special.

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Just a few thoughts come to mind regarding your idea.

How far above the floor surface will it stick up? Or will it fit flush with the bamboo flooring? Sticking up just a little could become a tripping hazard. 1/4 inch or less with a round over would decrease that by quite a bit.

In regards to strength if there is open space below it you could put angle iron around the perimeter with an angle iron center brace or 2. I don’t think you would need a full perimeter but just need to be careful they are all the correct depth within reason (shims if needed for correct height). Paint the angle iron black so it disappears under the grate.

Hole diameter - you might want to do a couple tests on some scrap wood with the hole pattern and size to see what it feels like to step on with bare feet. 1 inch holes might grab toes and may be a big issue with small children fingers and toes (or pets). Unless you go with really small holes you might want to install screen (like 1/4 wire cloth) onto the bottom to prevent items dropping into the bottom of your furnace air intake/return. You may want to think about rounding over or putting a slight bevel on each hole also.

Hole pattern - I would use my MPCNC to do the hole layout with a 1/8 bit on a piece of 1/8 hard board sized the same as the finished grill and just use a center punch on the 1/8 holes to mark it for the forstner bit.

Just a few quick ideas



I had not thought about my toe getting caught in it, but looking at current grill which the slots are 7/16" x 1-7/8" that is probably not a problem. I will make a version with 1/2" holes to see the difference though. I had thought about doing test drills in a scrap piece & will do that before attempting final version. There is a filter under the grate, so anything that falls thru will land on that. No kids at this house, so do not need to make it child proof. Thanks for the comments. The hole layout I will probably print on a sheet of paper to start with & tap a nail at each spot to mark it. I found this drill guide I might modify to use with the bits I have or use my small drill press. I might have to slot the hole of this jig for it to work with my bits since my bits are 5/16" OD near the end & 3/8" for the drill chuck.

The 1/4 scale plastic part seems quite strong & if I had a printer that could go this big I would 3d print one to see how it felt.

I just looked at 1/2" holes & air flow goes from 34% to 38% and 561 holes instead of 133 1" holes. I accidentally changed the spacing to 1/4" before realizing I meant to use 1/2" spacing (I had a couple of beers before drawing this up today). That is a lot more holes for 4% gain if the 1" holes are not a problem for my feet with 1/4" spacing between the holes. I will drill a test board with 1" holes to see how it looks & feels. If I used 1/2" holes with 1/2" spacing it would be 23% airflow & 337 holes, so I am liking 1" holes if they do not bother my feet.

Wood should have good protection from water and high humidity. Otherwise it may became too weak after a while.

I had a case when wheel broke wood cover on a hole because it was wet at down side for a long time.

If you look at the commercial wooden vent covers they tend to use slots, with the slots angling ever farther toward the outside as they get farther from center. That forces the incoming air to spread wider through the ventilated space. To implement that yourself would be a 2.5D cut instead of just 2D through hole.