I was looking at some pictures of castles in Europe and a thought came into my mind.
How did the castle builders keep watter from seeping into the castles from the moat? Today we have modern water proofing materials and powerful pumps to keep our basements dry, but what did they use back in the 1200’s? Or was stone fitting so good back then that castles were essentially water proof?
IIRC, they used clay and other nonporous materials. They built dams (and sewer systems/aqueducts) long before they built castle moats after all.
Did castles have basements?
Never played dungeons and dragons, huh? 
Good ones had wells, at the very least. Cellars are a nice feature too.
Even using nonporous materials I assume that cracks would have developed given the massive amount of weight that would be sitting on the foundation. Even today, using modern concrete and waterproofing materials foundation cracking is fairly common and leaks are not unheard of, especially in older structures.
I suppose they could have built the castle foundation above the level of the water… but from looking at photos that doesn’t appear to be the general case.
Lords and Ladies did not live at ground level. That’s for servants and/or horses. Basements are for prisoners.
That’s where the dungeons were. And who cared if the walls were breached?
Water seeping into the well shouldn’t be too much of a problem, surely 
Moats did not contain fresh water. They were unpleasant even by the standards of the day.
All the better for keeping out enemies, y’know.
Interesting, researching this topic, moat construction didn’t fit my preconceptions.
From ,“The Secrets of Medieval Castles”
Would think castle construction would have to accommodate the reality of the site chosen ie Those built on rivers made do with foundation footings and a first floor dungeon unless the specialty de la maison was water boarding.
I think water would infiltrate any space excavated below the water line unless it was in the center of the castle with enough earth and stone between the cellar and the walls. They had some form of grout, at least the Romans did, but keeping the gaps in those huge stones sealed over time wouldn’t seem practical. For a castle in the middle of a lake they would probably build on an existing stone island. I guess if they had the patience they could build up a stone foundation if bedrock wasn’t too far down.
Or they just build on top of the previous three castles which sank into the swamp. 
It had to be cold, damp, and smokey from fires burning for what warmth that would provide. I’ve read of people putting on heavy coats and furs when leaving a room with a fireplace to walk to somewhere else in the castle. So maybe dampness was just a fact of life. The peasants and peons weren’t much better off in their huts and cottages.
lots of serfs with buckets.
Azay le Rideau is sort of like that. <quick google> Scroll down to the picture of the inner courtyard. See how there is a row of open ‘windows’ running down the center? That is a wide hallway with stairs - the ‘apartments’ open off this corridor. As near as I can tell, it was always open, there did not appear to be any sort of holes where fixtures for draperies, windows or shutters would have gone. I suppose, not knowing the architecture of that period, they could have been ‘pressure fit’ into place, but I can’t really think of any really good way to have fixed windows or shutters into place without having left some sign of removed constructs.
The apartments are quite nice on the upper floors. The main ones we were in had huge fireplaces for heating, and provisions in the one set that was returned to original from the 19th century modifications had smoothly plastered walls, with very nice fresco work and hangings on pretty much all the walls to keep the drafts down.
<and the moat in Angers Castle has deer living in it 
I think in a few years I may have to take mrAru to see France other than the sub pens in Toulon and Brest:D>
A well is the first thing you think of when designing a castle. The wall is second. To answer the question, so-called dungeons were usually below main street level but above the water level. Not all moats are inundated year-round.
