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jim-in-ga 12-04-2011 06:58 PM

Hidden fasteners difficulties - TimberTech ConceaLoc
I went to fasten my first deck TimberTech boards using the TimberTech ConceaLoc hidden fasteners and I am having issues right out of the shoot. Per manufacturers instructions I raised the 2nd board to engage the fasteners then lay the 2nd board down but I find, even after tapping the board to better engage the fastener, that it is not reaching the fastener's gap tab and so I am not getting the desired 1/8" gap. The gap I get is inconsistent, 1/8" at the ends but about 1/4" in the middle. The boards don't seem to be warped. What could be going on? How can I get the 2nd board to be seated all the way so it reaches the gap tab (1/8") so I can get the gap right? Is there something I can try without doing anything like is discussed in the next paragraph?

I already screwed in the 1st board on the outer edge. There is a porch wall on the outside so I don't think I can easily bend the 1st board inward if I unscrew the 1st board. I may be able to unscrew it and get a pry behind it to try to bend it inward. Can I unscrew the screws now and still re-screw in the same holes? I have always heard that is a problem with composite decks.

robertcdf 12-05-2011 12:39 PM

Use a rubber mallet to beat it in the rest of the way. I think you are fighting the fact that wood frames suck and are quite often uneven due to crowning, shrinkage, wanes, etc.

Adam@TT 12-05-2011 05:13 PM


I am an Associate Product Manager at TimberTech and I would like to help you solve this issue. If you could email me your your phone number, I will call you and we can find a solution to your problem. My email address is I look forward to hearing from you.

Adam Tindall

dvatt 12-05-2011 05:39 PM

Never had this problem and I install thousands of sq ft of tt

jim-in-ga 12-06-2011 09:12 AM

Coaxed the first board straight
I ran a string above the first board and saw it was slightly bowed out. I coaxed it inward in the middle of the board with some wedges (putty knives, joint knives and paint stirrers) between it and the neighboring porch. I let them sit between the board and porch structure while I put my screws and fasteners back in place. Good news, it seems these TT face loc screws can be screwed/unscrewed/screwed back in numerous times and they still hold when you put them back in - I must have done this 4-5 times.

debbifuller 09-20-2012 05:57 PM

Timbertech concealed fastener issue - solution
Hi Jim, we just had the SAME issue. After talking with both Timbertech and the manufacturer of the fastener, we now have isolated the problem and also found a solution. The fasteners were manufactured to Timbertech's specs but the screw even when screwed in at the suggested 45 degree angle sticks out farther than the spacer! Our solution, after discussing this with Timbertech and verifying that it won't cause issues with the decking later, was to rout out a small area in the decking directly where the screw makes contact with the next board. (We used a 1/2" radius roundover bit). Now, the deck board will seat easily when attached to the fasteners. It was time consuming and should not have been necessary but it worked and our decking now has even, precise 1/8" spaces between each board. You could also achieve the same thing by beveling the entire board to allow this clearance. Timbertech should do this themselves if they continue to sell this fastener system. Both Timbertech and the fastener manufacturer were aware of the problem but had not addressed it. If you don't make these adjustments, you will get spacing between 3/16th and 1/4 inch! You can beat on it all day and it will never work unless you rout out the board.

ghhartmann 08-23-2013 11:50 AM

Tight Gap with TimberTech COncealoc
The CONCEALoc and any grooved TimberTech do give a 1/8" gap. Here are some things to look for and possible solutions for any trouble you may be having.

According to the TimberTech installation manual side to side gapping should be a minimum of 1/8” to 3/16”
Causes and Solutions
Not measuring gap correctly. Because the board is radiused the gap looks larger than it is. It is difficult to measure. Use of a drill bit is the easiest way to measure the gapping. If a 1/8" drill bit can pass through the side to side gap just barely touching the sides you are good.

Not using CONCEALoc. Is the clip you are using metal and colored brown.

Boards are not correctly fastened to joists. Unless the boards are fastened down to the joists you cannot get the 1/8" measurement. A minimum of 3 boards must be installed side to side to have an accurate measurement.
Not enough effort. Maybe you just aren’t pushing hard enough. The head of the screw must indent into the bottom radius of the deck board. This takes a lot of effort. It does not cause any structural damage or loss of integrity to the deck board.

First board not installed straight. If a single board is not installed straight this will cause issue with each following board. Use a long straight edge or a taut string to determine if the board is straight. If the first board is installed along the side of the house it is very likely not installed straight. Rather than follow the wall you should snap a line to place the first board.

Joists are not level or at consistent height. A straight edge or level can be used to check that all joists and ledgers are level. If they are not, the clips will be difficult to fully engage into both boards.

Screw not driven at 45 degree angle. The screw head does come in contact with the bottom radius of the deck board. When installed at a 45 degree angle the board interference is minimized

Clip too tight Too tight and it is difficult to install the board. NO IMPACT DRIVERS with any clips.

Clip too loose. Too loose and the screw interferes with the oncoming board. Deck boards will also feel loose underfoot, end up noisy, and move with temperature fluctuations, buckle and sag.
If anyone has any difficulties after reviewing these instructions call me. I am with the clip manufacturer. There is no issue with the board or clip.

Greg Hartmann

Reisen 10-28-2013 09:32 AM

Just wanted to say thanks to Greg for the great post.

I just installed about 200 sq ft of Timbertech with ConcealLoc last weekend. Being completely new to this, I didn't think about the fact the edge of my house wasn't straight, and sure enough, a string line showed that my first board was bowed. I straightened it out, and am now very happy with the gap. A couple of other notes:

- The clips will actually pull the boards together. This may have been obvious to most, but I didn't think about it until I started screwing down the clips. So, if you can't get the gap perfect just placing the board on the clip and hitting it with a 24 inch piece of scrap, driving the screw into the clip will do the rest of the work.

- I don't see any need to rout the bottom of the board. Hitting it with a piece of scrap indents the plastic just enough, maybe 1/8 of an inch.

- I used a plastic dead-blow mallet, which was effective, but I did ruin two boards with mi****s (hit right at the edge and splintered the plastic). Definitely safer to use a piece of scrap.

ghhartmann 10-30-2013 12:14 PM

Evidently moderators will not allow my phone number. The clip manufacturer is FastenMaster.
Google Greg Hartmann FastenMaster and you will find my phone number is listed in several places.


FastenMaster has a website with our phone number listed. Call and ask for Greg Hartmann.
You will be forwarded to my cell.

I am available to answer any of your deck fastener questions.

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