Nails Not Flush On Hardibacker. Should I Pound On? - Tiling, ceramics, marble - DIY Chatroom Home Improvement Forum

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Old 04-07-2013, 04:51 PM   #1
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Nails not flush on Hardibacker. Should I pound on?

Greetings all!

Am really getting good info from this site BTW!

I've installed 3x5 1/4" Hardiebacker (over 3/4" exterior ply on 2x6 joists on 16" centers) using Custom Building Products fortified thinset mortar, a 1/4" notch trowel, and 1-1/2" EG roofing nails. This is in preparation for 12x12 porcelain tiles in a 92 SF bath area.

I could have done a better job getting the nail heads flush; some protrude 1/8" or more, more than enough to make troweling the tile thinset a PITA.

1. Can I use a drift punch to set these flush or will I compromise the backerboard and / or thinset? The thinset has been curing about 18 hrs.

I filled the gap of 1" between the Swanstone showerpan and the adjoining Hardiebacker with 1/2 and 1/2 mix of above thinset and Type S mortar. I figured the gap was too large for caulk. Am planning to Redgard over this (the area near the shower exit) and under the neighboring sink, about 4' out to cover the 1st backerboard joint. (Yes, I could have laid out and cut the backerboard more precisely.)

2. Is this okay?

I left the 1/4" gap between the wall board and the backerboard as instructed by Home Depots Tiling 1-2-3 book. They didn't tell me what if anything should go in the gap. The wall board doesn't extend all the way to the plywood substrate and in some areas there's a 1/8" gap above the backerboard and the wallboard. From this site, I understand I can use an exterior siliconized acrylic caulk to fill the gap.

3. Should I Redgard over the joint between the backerboard and the caulk all around?


Last edited by Hal_Ferguson78; 04-07-2013 at 08:52 PM. Reason: Added Hardibacker dims
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Old 04-08-2013, 04:44 PM   #2
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I'd certainly get those nails flush. Just be careful doing so.

For the other questions, please post some pictures.


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Old 04-09-2013, 03:04 PM   #3
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The mysterious 1/4-inch gap

Thanks Seattle. I didn't hear back from the thinset manufacturer so I just went ahead put the heads flush using a 1/4-inch carriage bolt and my trusty hammer.

I'm going to (attempt to) post a couple photos.

On my question 2, above, I've already rolled some Redgard over the mortar adjacent to the shower pan and up the pan an 1/8-inch or so. Am trusting that the mortar will be okay. You can see the before Redgard photo in the Shower_Pan photos.

Am still not sure what to do with the 1/4-inch gap between the backer board on the floor and the drywall. I'm thinking of filling with some siliconized acrylic caulk, enough so can roll some Redgard over it and up the drywall a bit. You can see the gap at the exterior wall adjacent to the entry and also the gap at an interior pony wall.

Also, the 1-inch gap between the backer board and the raised door threshold is visible this photo. Am thinking I should have filled this with some of my mortar mix. This is an exterior door and though water hasn't been getting in, it can rain something fierce here.

4. Can I fill this 1-inch gap with type S mortar (have some left over from the shower pan bed), and then Redgard over it prior to putting the porcelain tile down?
Attached Thumbnails
Nails not flush on Hardibacker.  Should I pound on?-exterior_wall_pony_wall_backer_junction.jpg   Nails not flush on Hardibacker.  Should I pound on?-shower_pan_backer_junction.jpg   Nails not flush on Hardibacker.  Should I pound on?-shower_pan_wall_junction.jpg  
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Old 04-10-2013, 05:28 AM   #4
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Get your hammer and set those nails----did you follow the manufacturers nailing pattern? Durrock calls for nails every 8 inches---not sure about Hardibacker----
New members: Adding your location to your profile helps in many ways.--M--
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Old 04-10-2013, 07:39 PM   #5
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Nails set flush. Trust mortar bed okay.

Thanks for the encouragement Mike. I've set the nails flush. Hardiebacker actually has nice molded indents for attaching hardware. Through no fault of her own, my assistant pounder didn't locate the nails at the nice molded points, but did approximate the proper spacing.

I've since put mortar (see above) in the gap between the shower pan and the adjacent backerboard, applied two coats of Redgard to cover mortar, about 1/8-inch up the Swanstone showerpan, and across the joint to the neighboring backerboard, the one next to the one adjacent the shower pan.

Failing any other ideas, I also ran some paintable caulk in the 1/4-inch gap between the backerboard and the wallboard, enough to provide a seal between the two. Not sure what else to do with the pesky 1/4-inch gap. Will apply Redgard as quantity permits.

Absent any other thoughts, I'm going to mix a bit more of that Type S mortar with some thinset and fill in the 1-inch gap at the entry threshold (pic above). Am thinking the acrylic in the thinset will help bind the Type S mortar. I'll leave 1/4-inch between the mortar and the backerboard which I'll fill with paintable caulk. Then will Redgard over the lot and 1/8-inch up the threshold piece.

I sure hope this does it. Never done any tiling before and am not all that sure I ever want to do so again.
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gaps , hardiebacker , redgard , shower pan , thinset

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