Where did Hogwarts' building materials come from?

Question

It is known Who built Hogwarts?, but what did they use to build the castle physically?

There was obviously magic used to for the construction (changing floor plan, Room of Requirement, etc.). This would mean the materials were enchanted at some point. However, where would the raw materials come from? They were trying to build the castle away from the prying eyes of Muggles, so any large supply chain operation of mining raw materials, transporting them, and erection would surely be noticed.

Is there an evidence that other materials (e.g. trees, grass, small rocks) on the grounds were transfigured into the stone blocks and other pieces used to construct the castle?

Answer 1

We don't know.

There is nothing on this topic in canon, so maybe we should do a bit of... speculation.

We know that in that time period, Muggles were building castles. Lots of castles. Everybody had one. And obviously they were getting their materials from somewhere.
So, speculation #1: They mined it all and then enchanted it before/after building, just like the rest of the world. They could have used magic to mine it, or at least make it easier.

Speculation #2: Magic. They could have bought or mined a few, and duplicated them, as @A.Darwin stated above.

Answer 2

Hogwarts castle was built by the original founders - Godric Gryffindor, Helga Hufflepuff, Rowena Ravenclaw, and Salazar Slytherin.

The exact date is unknown, but from what Hermione says in Chamber of Secrets it was at least 1000 years ago (and she would know, having memorised Hogwarts: a History).

This would put construction at sometime in the 10th or 11th Century, the Middle Ages in Europe. We also know that Hogwarts is somewhere in the Highlands of Scotland (taking into account several sources, not least the journey time from London, the fact that they always travel north to get there, and of course the geography around the castle).

In the mid 900s AD Scotland and England had an amicable relationship, although this had deteriorated by the turn of the century and there were several military campaigns conducted amongst several Scots fighting for their own crown. This was the time of Duncan and MacBeth, heroes of the famous Shakespearean play. Needless to say, with all that was going on, it is likely that the wizarding society present in the British Isles kept itself isolated from Muggle politics. This is probably one of the reasons Hogwarts was built in the Highlands, which were sparsely populated. With the addition of some magical concealment, it would not be hard to keep non-magical folk away from the castle.

As for resources, we don't really know much about magical construction. Muggles at the time were building great castles themselves across the country, so it's not really that hard to imagine a small group of witches and wizards doing the same, albeit with magic in place of manpower. Rock was mined from the ground; wood from the forests. Glass and metal could be forged in magical fire, or transfigured from other materials. Earth and stone can be levitated into place and bound magically. I can imagine the groundwork for the castle being produced in a relatively short time; it could be that Hogwarts was originally a small project, which was added to over the years as more students arrived. The magical population is relatively small; in the Middle Ages it would have been even smaller.

We know from Hermione that the castle today is unplottable, and that a Muggle would see nothing but a dangerously crumbling ruin if they set eyes upon it. I think it is reasonable to assume that these basic concealments have been on the castle since its construction, and the spells were expanded whenever more buildings were added.

Answer 3

There's always the confundus charm or the memory modification charm. Even if any pesky Muggles happened to see the masssive orders being placed for stone and other stuff, just wipe their memory. Easy-peasy.

Also, the founders didn't really have to mention that they were building a magical castle which defied all known laws of phsyics (At least what passed for physics in those dark, dark times).

The founders could easily have mined the stones themselves or with the help of other wizards.

Answer 4

There could be protection put up around the place where they were building Hogwarts, just like protection around the woods of the Quidditch World Cup - which if Muggles come near the place they remember some appointments and turn away (Arthur Weasely says in book 4). They work for months to make these protections.

But the founders of Hogwarts were much more powerful than any wizard, for they have built a school for magic. They could easily have first created protection then build the castle.

This can also be seen, though it's small, how the trio (Harry, Ron and Hermione) protect their hiding place in Deathly Hallows - first create protection around the place, then erect the tent.

For materials they could have bought it, or just used emino curse over one block to repeat them.