From a single player, not really. There is some ways for a single player to do some server hits, but not from regular buildings (they have to intend to slow down the server).
Usually server admins and owners don’t allow foundation spam because if you let one do it, everyone can. When you have many people doing it, then you can have some hits on performance. But like darth said, its not just foundations. Its everything. Walls, doors, windows, roofs, floors, ceilings, placeables, etc.
The biggest offender for server lag is typically storage. More often than not, players turn into packrats and store everything they pick up. There’s little reason to do this, so encouraging a community to use the stuff they loot or discard it is best.
There’s a myth about foundation stacking that has been dispelled for years, but is still apart of Conan Exiles folk tales that some ignorant server admins and owners still believe in. The myth goes that foundations have special scripts involved and stacking them means there is more foundations than needed. They recommend the asinine advice of using walls and pillars to replace foundations where you can.
Foundations, Pillars, and Fence Foundations use the exact same calls to exert landclaim as each other. Using a pillar has the exact same performance hit server side as a pillar. And walls don’t have much less if even less, as well as other building pieces.
If you’re seeing a drop from 60 to 30 FPS then there is something wrong, and may not be related to building spam (especially if you’ve been keeping it clean). Try checking your logs and see if there’s any errors and warnings. Usually when FPS starts dipping and there isn’t many players on, there’s a repeating error or warning going off several times a second (or more).
You should see LogServerStats: Status report over and over every minute or so and only that. With an occasional warning saying it cannot connect to webserver. Both messages are related to the server browser, the first one is how the server talks to it and let’s anyone browsing servers see your server, it updates once a minute. Sometimes it will throw an error because it couldn’t talk to the browser. Either it just didn’t get through for whatever network reason or Funcom’s web server got congested or went down (this happens sometimes). If you see a lot of network errors then check the forums to see if there is an outage, if not then there is something going on with your provider.
Errors that repeat over and over usually mean there is an outdated mod or a removed mod with entries that are still calling to functions that no longer exist. You can use a SQL command on the database to remove these items if needed.
If none of that works, then you have a bit of database corruption and need to consider a wipe in the near future. As the problem with persist and not really get better.
40 players is what the game is designed for by Funcom. We have the ability to go higher when using heftier hardware. If you’re seeing the game tank on less than that, then you need to contact your provider and get them to see if something is wrong. If you’re paying for slots, then you need to be able to fill those slots.
If they give any other answer than “We’ll look into it and get this fixed ASAP” then switch providers. Providers should not be advertising slots that they are incapable of providing for.