There isn't a quick fix to this as she has a pretty considerable issue.
Pumping in super latex or using a flowing 2 part epoxy to lock the tiles down will take time.
A combination of both generally seems to work best.
By drilling holes or injecting in thru grout lines you have to push and pull the product into the hollow voids.
We use vacuums and rubber mallets to circulate the products thru sections of the floor.
Best to do area then weight them down.
You can tell when the subfloor is responding as it sounds less and less hollow.
Make sure your product doesn't end up on the floor below.
This is generally caused by a bad install.
Limestones can wick the moisture out the thinset and have bonding issues.
Stone installers will wet the limestone prior to installing to avoid this.
Charge a good rate as this is a specialized repair.
I would remove all the grout once the tiles are locked down and re grout mixing with latex.

Sent from my iPad

> On Apr 16, 2015, at 8:17 AM, N-Motion Stone and Tile Care <klhudson@atlantastoneandtilecare.com> wrote:
>
> Chris,
> You could try In-Ject-A-Bond to re-bond the tiles to the sub floor. However, check to ensure that the product is safe to use on the heating system.
>
> Kevin L. Hudson
> N-Motion Stone and Tile
> (678) 662-0110
>
>> On Apr 15, 2015, at 5:37 PM, Chris <csantospago@gmail.com> wrote:
>>
>> Hi partners
>>
>> I have a client with a 5 year old renovation. We did all the countertops. The builder screwed up the limestone floor. Big 12x36 tapered limestone tiles with radiant heat underneath.
>> Many of them came loose within the 1st few years. She hired another floor guy to fix it. He said the 1st floor guy used the wrong cement and he replaced with correct cement. I guess most of the tiles came up in one piece and he just re installed them.
>> Now she is having the same problem. Many are cracked and 1/4" grout lines are all cracking.
>> She will put the house on the market in May and just wants a quick fix.
>> I've heard of some tile installers using a glue or cement that will hold the tile in place so it doesn't vibrate and crack tile or grout.
>> I would like to fill some of the badly cracked tiles and also spot repair the grout.
>> Any thoughts on what I can use to inject alongside the tiles while they are still in place?
>> Thanks Chris
>> Sent from my iPhone
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