I'll try and explain your issue as thoroughly as possible. Some further information would help pinpoint the exact issue, but I'll touch on several common causes for your issue.
Pictures always help, so if you can post some, they could provide further important information.
Here's a list of things that would be helpful to know...
- How old is the home?
- Since you said that you put new underlayment down..
- Is it over a basement or a crawlspace?
- If it's over a crawlspace, is there a properly installed vapor retarder installed in the crawlspace?
- Is the crawlspace properly constructed and ventilated (Minimum 18" height with cross ventalation)?
- Prior to installation was the floor checked for flatness (not level, but flatness)?
- If the floor needed leveling or patching was it done properly?
- Are the areas that are showing gapping receiving direct sunlight?
- If so, do you have window blinds, shades, or curtains that can be used in those areas?
- Do you happen to have a laser thermometer?
- If so, can you record temperature readings of the flooring at the hottest, sunniest times of the day?
- Is there adhesive oozing up through the gaps?
- If so, is it dry and sticky or does it look like the consistency of mayonaise?
- Is there any noticeable odor?
- How is the floor being maintained?
- Is a steam mop being used?
- What specific maintenance products are being used?
- How frequently?
You mentioned that on the first install the used the Karndean K-99 HM. When they applied the adhesive to the substrate, did they do the entire area all at once or did they spread only small areas and then lay into them?
- That adhesive (K-99) only has a two-hour open time. Given that they were dealing with brand new underlayment, if they spread the whole area up first and then started laying into it, they more than likely "lost" the adhesive. Meaning that they went beyond the maximum open time, and they weren't getting any wet transfer to the back of the flooring. Once this happens, it's just a matter of time before gapping or curling starts to occur because you have little to no bond to the substrate. This would also be exacerbated if they used too small of a notch trowel to start with. You would lose the adhesive faster, due to the absorbency of the new underlayment.
- If the area is exposed to a lot of direct sunlight and the flooring was not adhered properly, the daily heating and cooling can cause enough movement in the product that when combined with a weak bond would cause gapping to occur.
- I noticed in their installation instructions that they recommend a specific adhesive if the floor is going to be above 122 degrees Fahrenheit. In my experience with other products and manufacturers, that seems to be on the lower end of the spectrum. It's not uncommon for floors to reach 140-150 degrees if they are exposed to direct sunlight.
What I'm trying to say here is that given the fact Karndean agreed to replace this under warranty, they might know they have a lower tolerance for heat and may have experienced a problem with the product previously. Otherwise normally, this would have been pinned on the installer as installation related.
Not following or understanding the adhesive instructions under LVT is probably the number one cause of failure I see. The main issue is guys want to go in and glue up the whole floor, let the adhesive tack off and then start laying the floor. This will almost always lead to a failure. We are seeing a massive movement within the flooring industry to move back to a semi-wet or wet set installation method because of the Tsunami of failures installing into pressure sensitive adhesive is leading to. However, the 3rd part adhesive manufacturers are being slow to adapt because it means the installers, who are their primary customers believe that they won't be able to install as fast and won't want to use their product.
I know this is going to be an unpopular opinion among my fellow professionals on here and I'm sure I'll here "I've never had a problem". The reality is two things you should ALWAYS do with a glue down LVT. First always install it in a semi-wet (peaks of trowel ridges are cloudy and troughs are clear) or wet set method. Number two is NEVER roll on an adhesive. Always use a proper notched trowel. A trowel is a proper metering device that can be checked for the proper amount of adhesive consistency a 3/8" paint roller is not.
From a "rulebook" (read legal) standpoint here's the bottom line...
I'll put it into a real-world scenario. You're installing brand X flooring, let's say Karndean for example. You choose to use Brand Y adhesive. However, when you read the instructions on the adhesive, they do not agree with the flooring manufacturer's installation instructions for the flooring. For example, the adhesive says use one size trowel and the flooring manufacturer says use a different size trowel. YOU 100% MUST FOLLOW THE FLOORING MANUFACTURERS GUIDELINES - NOT THE ADHESIVE MANUFACTURER. If there is a failure and you do not follow the flooring manufacturers guidelines for the product, then you have installed outside of the recommended installation guidelines and there is no warrantable recourse.
Maintenance can also cause issues and the problem will also be exacerbated by an initial weak adhesive bond, leading to gapping or curling of the product. Too high of pH, or using steam (steam is a minimum 180 degrees) for example can further weaken a bad install.
Again providing some photos and some additional information would go a long way to helping pinpoint the problem. If I had to guess what caused your issue with the information currently at hand, I'd say the installer didn't follow the time limit on the glue on the first installation. On the "spot" replacement they realized they didn't get enough transfer and so tried to use a larger notch to create the transfer, but in reality, they didn't install the replacement before the maximum open time of the adhesive and essentially repeated the same issue from the original install. Without a proper bond, once exposed to maintenance, traffic, and any source of heat, the product will begin to change dimensionally.
I look forward to your reply and wish you all the best in getting your situation corrected.
