Mortar Base Over Plywood


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Old 02-18-12, 07:00 PM
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Mortar Base Over Plywood

I'm about to set a fiberglass shower pan in a mortar base over a plywood subfloor and was wondering if I need to use a primer first before pouring.
 
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Old 02-19-12, 03:09 AM
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Primer or plastic sheeting. Anything to keep the mortar base material from having the moisture sucked from it prior to setting. What are you using, as you said "pouring". You should probably use something like thinset. Makes for a better bed and won't run out.
 
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Old 02-19-12, 03:30 PM
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What he said............do not let the mortar touch the plywood, it will swell, buckle, warp, etc., etc. The mortar material should be very slow setting and flow somewhat, to give you time to install the tub after pouring the mortar. All this assumes that the tub manufacturer recommended such a base.
 
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Old 02-20-12, 07:03 AM
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Ok. So I'll apply either a primer or plastic sheathing first. Not sure if the manufacturer of the shower pan recommends a mortar base or not, but I used a mortar base when I remodeled my master bathroom and really like the solid feel it gives. Are there any reasons why a manufacturer would not recommend it?
 
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Old 02-20-12, 02:39 PM
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Yes, some bases are structurally built so no further support is needed. In fact, applying thinset, etc. would make the base unstable. That's why Bill suggested checking the manufacturer's specifications first.
 
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Old 02-20-12, 03:31 PM
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I have done a number of shower bases where the manufacturer recommended neither a mortar(or other) base and no membrane needed. I do use some kind of membrane.
 
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Old 02-21-12, 07:57 AM
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I'll definitely check with the manufacturer, but it seems like as long as the mortar (not going to use thinset) fills the majority of the voids in the bottom of the pan then I should be ok.
 
 

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