Soffits with MDF? - AVS Forum
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post #1 of 14 Old 12-17-2010, 09:21 AM - Thread Starter
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Hi all,

I will soon need to cover my framed soffit (2x2s) with MDF. The soffit was built after the room was drywalled. Soffit will eventually be covered with fabric.

How is everyone attaching MDF to their soffits? I am inclined to use course thread wood screws, but wondering if there is a better way. Also is predrilling necessary to prevent splitting?

Thanks!
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post #2 of 14 Old 12-17-2010, 09:29 AM
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Quote:
Originally Posted by WannaTheater View Post

Hi all,

I will soon need to cover my framed soffit (2x2s) with MDF. The soffit was built after the room was drywalled. Soffit will eventually be covered with fabric.

How is everyone attaching MDF to their soffits? I am inclined to use course thread wood screws, but wondering if there is a better way. Also is predrilling necessary to prevent splitting?

Thanks!

I just used coarse thread drywall screws. I don't recall drilling first (don't think I did).
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post #3 of 14 Old 12-17-2010, 09:44 AM
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Quote:
Originally Posted by WannaTheater View Post

Hi all,

I will soon need to cover my framed soffit (2x2s) with MDF. The soffit was built after the room was drywalled. Soffit will eventually be covered with fabric.

How is everyone attaching MDF to their soffits? I am inclined to use course thread wood screws, but wondering if there is a better way. Also is predrilling necessary to prevent splitting?

Thanks!

They actually make screws specifically for MDF, but can use drywall screws if you wish. Pre drilling will make it easier, but probably isnt necessary except for any places you are very near the edge...you might want to pre drill in those spots.

The screws wont sink into the MDF very well, so if your fabric is going to lay flat against the MDF you may consider using a counter sink so the screws will be more flush.

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post #4 of 14 Old 12-17-2010, 09:47 AM
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Quote:
Originally Posted by premiertrussman View Post

The screws wont sink into the MDF very well, so if your fabric is going to lay flat against the MDF you may consider using a counter sink so the screws will be more flush.

Excellent advice

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post #5 of 14 Old 12-17-2010, 09:49 AM
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I always use a pilot counter sink bit with mdf it makes the job much cleaner.
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post #6 of 14 Old 12-17-2010, 10:01 AM - Thread Starter
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Thanks guys! Pilot hole, countersink and drywall screws it is.
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post #7 of 14 Old 12-17-2010, 10:19 AM
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Or liquid nails and a 16 ga nail gun ...

It appears my hypocrisy knows no bounds.

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post #8 of 14 Old 12-17-2010, 10:30 AM
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If its going to be covered with fabric, why not fill with some fiberglass and cover with fabric (no MDF), to get some bass trapping out of it?
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post #9 of 14 Old 12-17-2010, 10:52 AM - Thread Starter
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I thought about that... But would need to figure out a way to incorporate can lights and a rope-light tray.... Any ideas?
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post #10 of 14 Old 12-17-2010, 10:57 AM
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Check the last page of my build thread, I'm doing something like that - the bottom is open and filled with insulation (added a layer of rigid insulation since those pics), and I have a rope light tray and recessed lights. Also check Moggie's thread, and Sandman's.
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post #11 of 14 Old 12-17-2010, 11:19 AM
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Adding the MDF will act just fine as a bass trap. The MDF won't add up to a hill of beans compared to most low frequency wave lengths, and the addition of the MDF will actually enhance the bass trapping characteristics. A wavelength that passes through the MDF will be attenuated, and it will be attenuated even further when a portion of it is reflected back through the MDF making for reduced SPL. Keep in mind as well, your whole room is one big bass trap. Brad is correct in that you should put some insulation in there. Hope this helps! Best wishes!

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post #12 of 14 Old 12-17-2010, 09:34 PM
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You can counter sink the drywall screws on MDF without going through the effort of pre-drilling. Just make sure that you are not screwing it in close to the edge or it will crumble it. People have been doing this in the car audio business for years and it just takes practice.

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post #13 of 14 Old 12-18-2010, 06:49 AM
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The typical method is to install 2x2's on the wall and ceiling using screws and a construction adhesive. The screws through the 2x2's should anchor into your HAT channel (if that's what you are using). The soffits (preconstructed) are then raised into place and screwed into the 2x2 runners without construction adhesive. This provides a more secure anchorage and allows for easy future removal of the soffit if required.

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post #14 of 14 Old 12-18-2010, 07:16 AM - Thread Starter
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Thanks all for the feedback. My soffits are up... without construction adhesive. I did build a full "box" soffit out of 2x2s, then lifted it into place, and screwed through into hat channel. I also screwed horizontally into studs on sides. I did shim around the bottom to make sure the front part of the soffit was truly "vertical." I have found that my theater walls taper near the top, I assume from the extra tape and mud from the drywallers.

{after re-reading last post} Dennis - Fantastic idea... I wish I knew that earlier.
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