Prime and paint backs of pre-primed MDF baseboard?


Old 11-14-18, 07:25 AM
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Prime and paint backs of pre-primed MDF baseboard?

I am about to install new baseboards in our entire house. I'm using pre-primed MDF that is 4 1/2" tall. The backs of the baseboards are not primed and I was wondering if I should prime and paint the backs of the baseboards just in case any moisture gets behind them? Was thinking it may prevent issues down the line. Or would this just be a waste of time and paint? If I should, what is a good primer to use with with MDF baseboards?

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Old 11-14-18, 07:36 AM
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I certainly will not hurt if you prime the back side of the trim but it's not necessary. If water gets to the back side of the molding... you've got bigger problems than some damaged trim.
Old 11-14-18, 07:52 AM
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Just some time tested advice, I love MDF trim because it's super straight but absolutely will never use it anywhere it can be touched, meaning it's only used for ceiling coves and decorative trim.

MDF is incredibly soft and dents easy, if you have kids it will not wear well. I understand it's cheaper but for the durability I would recommend standard pine trim!
Old 11-14-18, 08:14 AM
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MDF paints beautifully but as mentioned it can't withstand much abuse. While priming the bottom edge and backside might help a little I'm not sure it'w worth the effort. Oil base primers will seal better against moisture but a decent latex undercoater is sufficient for painting.
Old 11-14-18, 08:31 AM
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would this just be a waste of time and paint?
Waste of time? Yes. But if there is a place where you KNOW it will get wet... bathroom or kitchen or basement, then THAT might be worth it.
Old 11-14-18, 09:03 AM
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Thanks for the advice everyone! MDF is pretty standard here (Arizona) maybe because of the low humidity but it's pretty much the norm in most houses here from what I've seen. When I was shopping for baseboards it also seemed to be what 90% of all the lumber yards carried. Anyhow, it's already purchased and delivered so will just go with that. No kids so shouldn't get dinged up too much. Was mainly concerned with say like mopping or something if water got underneath it.

I think I will paint and prime the backsides for the laundry room and bathrooms only.

Thanks again!

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