No. There is no way to skip file validation in Steam.
I can't support an issue specifically with regard to Windows 8 so if that's the issue, the only solution that I can propose is to wait until this software is officially supported on Windows 8.
There are alternative possible explanations. The following is based on my own experience with Steam doing this to me for TF2 and a similar case can be found here
When I first installed TF2 some time ago on a Windows Vista install, it exhibited this behaviour for me. The problem as it turns out was with my hard disk. By defragmenting my disk and my game, I managed to resolved the issue. You can try defragmenting the game files in Steam through the Local Files tab of Team Fortress 2's Properties page in the Steam Library, but I found using the OS's defragmentation tool was necessary if I recall. I'd recommend doing both just to be safe. You may need to validate files manually after this, but it should hopefully be the last time. At the time, there were no bad sectors reported and the hard drive was less than a year old, but fast-forward a year or two and that hard disk died on me so this may be an early indication of a problem with the hard disk that you may want to look into.