Hi everyone !I ve just bought some seats and runners and just wondering if it would be iva friendly to bolt the runners through the floor ?

idealy bolt then through a reinforced section of the floor. I also used large washers underneath to spread the load on the bolt, should I ever have an impact

I'm guess that your floor is steel and not aluminum.

If so its fine to bolts straight onto it.

For SVA it used to say that the seat only had to have structural triangulated strength/bracing if the seatbelt relied on it to hold or direct the belt.
In an impact I would guess the harnesses will stop the seat and passenger from moving more than the seat mounts.
I'm not saying don't make them as solid as possible (I always add bracing to the back for hard cornering support, not possible with runners) but it isn't the thing that 'retains' you.
If it is a track car I wouldn't bother with runners at all.
If it isn't, and you use runners, hope the seats are very rigid.
Also, I have before ditched runners to attempt to lower the seat and reduce weight.
For SVA the belt mounts had to be a given height above the bottom of the seat and this was a problem sometimes.
If in doubt, try and make the seat bolt holes the same layout as the runners holes and retro fit them.

For IVA you have to as a minimum use load spreading washers, I used 2mm thick 50mm square ones.
IVA manual has a diagram of acceptable seat mountings, it's worth a look, picture says a thousand words

Thanks everybody . Lots of good advice.