3 PCI-E slots but not enough room

[x34c]

I have a 1080 and a 1080 TI taking up quite a bit of room in there and I want to buy another TI soon but my 1080 is covering both slots.. I don't understand how this can be I have quite a good motherboard and you would think it would be designed to handle this.

http://www.asrock.com/mb/intel/Fatal1ty%20Z170%20Gaming%20K6/

Is there anything I can do maybe some extender??

 

[Aeacus]

I don't see nothing wrong with your MoBo. Also, most GTX 1080 Ti GPUs are dual-slot cards and they are supposed to cover 2 slots.

Since your MoBo has PCI-E x1 slots between PCI-E x16 slots, you can install 3 GPUs just fine to your MoBo. Despite GPUs looking cramped up, like on this random image from net:

But if you want to have more space between your GPUs then you need to build about similar mining rig as seen here:

 

[x34c]

So the x1 slots will run at 100% speed? and how exactly would that fit? or do you mean just because of the space the x1 slots are taking? Didn't really fully understand.

 

[Aeacus]

The PCI-E x1 slots aren't used at all in multi-GPU setup and those serve as a spacer between PCI-E x16 slots.

In this image, each dual-slot GPU footprint is showed as a colored circle. For example, 1st (Red) GPU plugs into the rightmost PCI-E x16 slot while it's heatsink/fans overhang the 2nd PCI-E x16 slot from right. 2nd (Orange) GPU plugs into 3rd PCI-E x16 slot from the right while it's heatsink/fans overhang the 4th PCI-E x16 from the right. And so on.
While this example image has all PCI-E slots as x16 ones, your MoBo has PCI-E x1 slots between PCI-E x16 slots.