My experience is that a top quality tent will not leak, ooze or weep water through the floor. Quality is expensive (although expensive doesn't guarantee quality).

I now use Hilleberg tents. Neither one has ever leaked any water through floor or elsewhere. I do not use a groundsheet, and I've had them pitched in adverse situations.

In the past I've done the same with Bibler tents, and before that I used an extinct brand named Alpine Designs. In fact, I've never used a groundsheet for any of my tents in almost 40 years of year-round camping, climbing, mountaineering, and even (gasp!) motorcycle camping . The whole concept of using groundsheets under tent floors is a recent development; before that, tent floors were expected to keep the water out. Now, if your tent leaks or the floor punctures because you pitched it on some pine needles, the salespeople will sell you a fitted groundsheet for an unconscionable amount of money. This does not strike me as reasonable, somehow.

Of course I've also used cheaper tents, although they don't usually belong to me. They tend to leak unless seamsealed laboriously and repeatedly, and they ooze water through their floors. They also tear and puncture more easily, and they often photo-degrade more rapidly. There are various grades of nylon, polyester and other materials (mylar, for example) used in tent manufacture, different ways of sewing seams, and various grades of waterproofing treatments. Some work better than others, and some last longer.

Just something to consider. YMMV.

Mark

Edit: redundancy