| Author |
Message |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 257
Registered: 08-2004
| | Posted on Tuesday, July 28, 2009 - 04:57 pm: |    |
I always thought MDF is fairly dimensionally stable. I have some large panels, about 4 feet x 4 feet x 3/4 inch thick that are bowing from recent humidity in the air. They are painted and it appears some of the edges, which are covered w/ metal reveals, are not painted. Has anyone encountered this w/ MDF? Any input or knowledge about MDF? |
George A. Everding, AIA, CSI, CCS, CCCA
Senior Member
Username: geverding
Post Number: 477
Registered: 11-2004
| | Posted on Tuesday, July 28, 2009 - 05:46 pm: | |
Yes. Email me geverding@cannondesign.com and I will send you information on an issue we had recently.
The product standard for MDF (ANSI A-208.2)defines three classes of moisture-resistance (MR10, MR30 and MR50). Humidity can be a huge problem, made worse if the wrong MR class was used.
George A. Everding AIA CSI CCS
Cannon Design - St. Louis, MO |
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre
Post Number: 886
Registered: 07-2002
| | Posted on Tuesday, July 28, 2009 - 11:31 pm: | |
MDF definitely has some dimensional issues when the edges are exposed. the rate at which it "inhales" water increases with every exposure, and the panels essentially delaminate. in most cases, none of the composite panels can be used in a situation where the edges are exposed and be expected to hold up for very long. |
John Bunzick, CCS, CCCA, LEED AP
Senior Member
Username: bunzick
Post Number: 1072
Registered: 03-2002
| | Posted on Wednesday, July 29, 2009 - 09:10 am: | |
Also, if both faces are not painted or laminated or otherwise treated equally, you can have warping with any panel product. |
Randy Cox
Senior Member
Username: randy_cox
Post Number: 65
Registered: 04-2004
| | Posted on Wednesday, July 29, 2009 - 01:44 pm: | |
MDF is great stuff if the edges are sealed. my summer job for part of high school was priming and base coat painting signs for my father's sign shop. I pressed Bondo into the edges as hard as I could and then sanded the edges smooth before priming and painting. Those fully exposed edges lasted at least 20 years without any maintenance. They probably would have lasted longer, but sign paint fades away and has to be repainted to look good. |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 258
Registered: 08-2004
| | Posted on Wednesday, July 29, 2009 - 02:48 pm: | |
Since I am currently out of the office, and don't have my AWI book with me, can anyone tell me if they would say that sealing the edges and back is "industry standard"? The problem with my situation is that the original spec called for hardwood veneer panels, stained which my spec addresses. Unknown to me, they were VE'd to painted MDF, which my spec doesn't address, since there is no other painted wood on the project. So, the architect is looking for some "teeth" that it is "industry standard" to seal/paint exposed edges and the backside of the panels. |
(Unregistered Guest)
Unregistered guest
| | Posted on Wednesday, July 29, 2009 - 10:52 pm: | |
To quote Paneling Section 500A of AWI: "In cases where raw MDF is intended to have a clear or opaque finish, no edge banding is required."
To quote Factory Finishing Section 1500 of AWI: "Concealed portions of factory-finished paneling shall be finished with two coats of sealer or primer.
Back priming is required prior to installation of any factory finished woodwork over concrete or masonry partitions and strongly recommended, but not required, in all other instances."
Finally, to quote Installation Section 1700: "Priming and back priming are the responsibility of the general contractor unless specified otherwise."
Note: Minimum thickness of "core" material is dictated by grade. This also might affect your specific situation.
So...probably no edgeband, probably no backprime/sealcoat on neither back nor edges (since "concealed")? But had you been informed of this "change", you would have anticipated the need to specify backpainted MDF...right?
The other question is...did you originally specify AWI certification...and, maybe, that too was VE'd? You might want to talk with your local AWI rep and ask if that would HAVE been something that QCP would have "caught" before installation...if indeed you had originally spec'd certification and it WAS VE'd. |
John Bunzick, CCS, CCCA, LEED AP
Senior Member
Username: bunzick
Post Number: 1073
Registered: 03-2002
| | Posted on Thursday, July 30, 2009 - 08:48 am: | |
Still, I'm curious about the ambient conditions where this paneling was installed. I haven't seen this problem, though imagine it could exist in cases of moisture or high humidity. I call for paint or varnish on all surfaces of anything wood as a general rule. My experiences as a painting contractor, a general contractor and a woodworker tells me this is a must. |
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