Two RF amps rather than one?

Just about to embark on a ground floor house remodelling where the upstairs is staying largely untouched. All new wiring will be installed for the ground floor, but the aerial dis amp is in the loft. Question is, do I route all new coax cabling from the ground floor TV's to the loft or to the ground floor server room, and then take a couple of feeds between the two locations?

When you amplify a signal that's already amplified then you add a lot of noise. This has the effect of closing the gap between the signal level and the noise floor. That's a bad thing.

How bad this is depends on what the signal was like going in to the first amp, then how much the gap was closed by the first stage of amplification, and then how much further the signal is degraded by the second stage of amplification. The risk with two lots of amplification is that the signal level ends up too strong for some of the TV tuners. You then get problems that look a lot like poor signal level such as blocking and freezing, but in reality it's an overloaded tuner. The other problem is that the amount of signal noise is so great that there's insufficient safety margin between the signal and the background noise. The result again is signal break up. You'd have a hard time diagnosing this without a professional signal meter.

The simple answer here is to do the job right first time. Aerial gear isn't expensive. It's much cheaper to run the cables correctly now rather than pay for an installer to come trouble-shoot and fix things later, particularly when you've spent good money on building trades to get nice smooth walls before spending even more money on decorators to give that perfect finish that then has to be wrecked with remedial work.

If you absolutely have to cut corners then at least swap out the loft amp-splitter for one with a Full Power output socket. (Here's an example. Other makes and models exist). One feed from this will then run to a passive (unamplified) splitter to feed the ground floor TVs. I'd strongly recommend though that you get a proper aerial guy in to do that so that the signal strength and quality can be measured to ensure that the solution will work.

Don't forget to run extra coax and network cables while you are at it.