Hello:

The house is underway...

I have 2x10 spruce floor joists at 16” OC (span, beam to beam, just under 10') which is being covered with 5/8” Durastrand PointSix floor OSB.

I plan to finish the foyer, mudroom, bathroom and kitchen with ceramic tile and the balance of the floor with 3/4” hardwood.

My question is about “underlayment”.

I believe that I need underlayment under the tile but do I also need it under the hardwood?

If so, should I put down 1/4” throughout and then an additional layer on top for the tiled area so that the transition for tile to hardwood is flush?

Is there a better way?

Regardless of the final underlayment 'formula', what is the best way to attach the underlayment? Glue & screw? Glue & ring nails? No glue?

I believe that the underlayment should be applied at right andgle to the Durastrand with the joints off-set, right?

Should there be a 1/8' gap beteen all joints?

Should the underlayment be done before the internat 2x4 wall framing is done?

Thanks for any advice and suggestions about this.

Rob.

Robert, ........... You can actually install ceramic tile directly to a plywood deck , with OSB I am not so sure, I would recommend at least 1/4" hardi-backer board and a multi-purpose thinset, such as: Mapei - Ultra Flex ...........no inderlayment under hardwood

Ok First off the site you want to ask these questions is http://www.johnbridge.com http://www.johnbridge.com/vbulletin/deflecto.pl is a tool that calculates deflection base on joist type and depth , span length, species, distance OC, etc. Once you know the joists are ok you need to make sure the deflection between joists are ok. What you are trying to accomplish is a floor that has a basic maximum deflection of length/360 (L/360) for ceramic tile with whatever live and dead loads are needed. For framing that is 16” OC, total subfloor plus underlayment thickness of 1 1/8” will work without issues. I would consider going even thicker for travertine or other natural stone. This is overkill for the wood floor part, but if you do the whole floor that way, you can use any flooring, anywhere without worries. I would glue and screw a layer of ½” ACX using Tightbond 2 Use a lot of glue. Attach it perpendicular to the joist runs. 1/8” gap. Where the tile goes, I would also use ¼” tile backer over the ACX attached with screws and thinset. Now your thickness transitions should be about right to 3/4" wood floor. If the house was rained on a bit before it was dried in, check for edgeswell on the osb subfloor before adding the underlayment. You may need to sand the joints flat before adding underlayment. Good Luck Eric

Sorry, I don't know why gbt won't let me use paragraphs. Cheers, Eric

Thanks people! :)

Eric: If you use the 'Add Reply' button instead of the 'Reply', I believe you can create paragraphs.

That is how I wrote this post.

Rob.

'd just ad that you might not want to glue down the underlayment layer under the tile. I've done renovations where the underlaymet is bonded so well to the plywood that it has to be renoved and replaced. If all your plywood layers are glued together it could be a very difficult removeal.

Eric,

If you are using Internet Explorer, then from the menu:

select Tools, Compatibility View to turn it on.

Bob, I agree that separating subfloor and underlayment is not going to happen if glued. You can usually get up all the thinset if you need to retile. Not much fun though. Cheers, Eric

Hello:

I went to the web site recommended above and here are my results:

"For joists that are SYP or Douglas Fir, in good condition, 9.25 inches tall, 1.5 inches wide, 16 inches on center, and 9.5 feet long between supports, the deflection calculated is 0.119 inches.

This translates to a deflection of L / 962.

Since the maximum deflection for tile is L / 360, and for natural stone is L / 720, your floor is rated for Ceramic tile or Natural stone, Congratulations!"

I was hoping to not have to put down underlayment over the 5/8" PointSIX Durastrand Flooring.

For the tiled area, I was looking at:

Schluter^®-DITRA-XL

Schluter-DITRA-XL is the latest innovation in uncoupling membranes.  DITRA-XL provides the same four essential functions as Schluter-DITRA (uncoupling, waterproofing, vapor management, and support/load distribution), but is 5/16" (7 mm) thick, allowing for even transitions between ceramic tile and 3/4" (19 mm) -thick hardwood flooring and ceramic tile application on single-layer wood subfloors on joists spaced at 24" (610 mm) o.c.

(http://www.schluter.com/2080.aspx)



Has anyone had any experience with this product? Am I asking for trouble if I don't use underlayment?

Is there a problem with nailing hardwood flooring down on 5/8" PointSIX Durastrand Flooring OSB?

Thanks,

Rob.