# underlayment above subfloor?



## elementbldrs (Sep 26, 2010)

I've been debating with two different installers... were not sure wether we should put an underlayment abover subfloor for raised foundation then hardie.... so if demo was ever a factor we would not be hung up with thinset directly on our origianl floor. Thoughts??

I've done dozens of concrete slabs.... but rirst wood floor.


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## GO Remodeling (Apr 5, 2005)

Depends on what product you use over the Hardie. Marble requires stiffer floor than porcelain ceramic or vinyl. So double layer is needed. But you'll still need to thinset the Hardie down(and any other tile backer material). 

I want my installation to last. I don't worry much about the next guy's demo.


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## elementbldrs (Sep 26, 2010)

Oh I have all intention of thinsetting hardie down. Subfloor is only 3/4 w 16 oc joist withe short spans, but want this to obviously be trouble free. Doin trav 12 by 24 subway... a little nervous for stone to hold up though floor feels solid.


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## Splinter (Apr 5, 2005)

Do a second layer of ply for the natural stone. Stagger the seams from the ply below. Screw into first layer of ply, dont aim for the joists. Thinset and screw your Hardi, or better yet, use Ditra.

Add: use BCX or ACX grade ply, at least 1/2"....


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## elementbldrs (Sep 26, 2010)

Yeah that's what I'm plannin, I wish homeowner would go for ditra, but he's innvolved in the projest heavily... and wasn't really wanting to be my ditra guinea pig.... so with 3/4 subfloor and 1/4 hardie, what thickness ply we thinking? Not much structural till 1/2 inch me thinks.


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## elementbldrs (Sep 26, 2010)

Ahhh u beat me to the answer


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## SSC (Feb 8, 2011)

I agree with the second ply but why not make it 3/4".


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## angus242 (Oct 20, 2007)

elementbldrs said:


> Subfloor is only 3/4 w 16 oc joist withe short spans,


How short of spans?

ONCE the joist structure is sufficient, I'd use 1/2" BCX EGP and a membrane system. Ditra or NobleSeal TS are _very_ easy to install. No guinea pig issues. I'd rather have a _superior_ underlayment than worry about if a contractor can successfully spread 1/8" thinset and embed a membrane.


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## elementbldrs (Sep 26, 2010)

Sorry weekend hit and I drifted my mind away from this part of the job. I just split my joist spans with another set of girders, so I was 2x10 at 16oc with 12' span, deflection was a problem, so ran new girders to half distance, solves other problems in the overall scope, as well as stone delfection numbers (over l/2400 now!)

I'm pretty sure its goin down as another layer bcx 3/4 then ditra... I'm so happy to get a chance to try this system out, gonna do schluter shower kit as well. Questioning if any other brands are better priced tho??


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## ee3 (Feb 10, 2006)

better price or better product,lots of stuff can be cheaper!:whistling


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## elementbldrs (Sep 26, 2010)

True story... job is t and m and price isn't the bottom line, but heard good stuff about noble and such.


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## goneelkn (Jan 9, 2010)

Just did my first floor and surround with Noble TS, went alot easier than i thought. Only thing with the walls, could of used an extra 3 or 4 hands to hold it up while i mudded 2nd and 3rd walls.


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## ee3 (Feb 10, 2006)

Ive been known to sneek a nail in at the upper edge as a third hand.


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## JohnFRWhipple (Oct 20, 2009)

ee3 said:


> Ive been known to sneek a nail in at the upper edge as a third hand.


You and me both Eric. I prefer a wafer head screw as my helper of choice.


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## astor (Dec 19, 2008)

goneelkn said:


> Just did my first floor and surround with Noble TS, went alot easier than i thought. Only thing with the walls, could of used an extra 3 or 4 hands to hold it up while i mudded 2nd and 3rd walls.


I have used Dal Tile's version of Noble Bond EXT adhesive for shower walls(Paperless fiberglass drywall).DAL BOND adhesive very easy to spread and have a long working time. Less messy than mud and have strong grab.Coverage goes long way like 150 sf per gallon.
I have spread 12 LF wall(10 ft wide)at once and still had plenty of time for flashing while I measure, fold and cut the membrane. Once flashed (30 min) placed the Dal Seal right on. Less air to pull,firm rolling ground.
All by myself.
Looks like I will never use mud for membranes unless manufacturer calls for it.


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## ee3 (Feb 10, 2006)

I was going to toss out the ease of EXT vs Thin-set ,but was tring to avoid coming off like I was giving a sales pitch!


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## goneelkn (Jan 9, 2010)

> I have used Dal Tile's version of Noble Bond EXT adhesive for shower walls(Paperless fiberglass drywall).DAL BOND adhesive very easy to spread and have a long working time. Less messy than mud and have strong grab.Coverage goes long way like 150 sf per gallon.
> I have spread 12 LF wall(10 ft wide)at once and still had plenty of time for flashing while I measure, fold and cut the membrane. Once flashed (30 min) placed the Dal Seal right on. Less air to pull,firm rolling ground.
> All by myself.
> Looks like I will never use mud for membranes unless manufacturer calls for it.


Is that with or without the primer??


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## Bill_Vincent (Apr 6, 2005)

No worries, Eric-- we all know you NEVER pitch Noble. :whistling:laughing:


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