Roof Issues "Base is uneven"

[Larku]

What exactly does Base is uneven mean?
It seems lately anytime I try to make a roof, It gives me that message.
The ground is flat, By all normal Standards this should be fine.
But the game continues to give me this message.

Any help would be useful.

[Simsample]

Try the cheat:
constrainfloorelevation false
and then dragging the terrain level tool over the lot. Then,
constrainfloorelevation true
to turn the constraint back on.

[J. M. Pescado]

One of the irritations of TS3 is that they didn't learn the importance of FLAT PLOTS from TS2, and so even seemingly flat terrain is, if you zoom in closely, highly irregular. At least the FLATTEN tool still exists.

[Larku]

Ah, I should have known.
I'll take note of that in future lots.

I got Frustrated and gave up building a roof over the Patio.

[Zazazu]

Placing columns and putting down floor tiles on the level you want the roof at can also help. I had one particular odd lot where most of the house was on diagonals that was a major pain in the ass.

[Catangi]

I have the same issue occasionally. Sometimes I can fix it using the tricks suggested above, but other times, the only thing I can do is demolish everything on the lot and start over. I also run into the same problem with stairs. One of the houses I built has no stairs for the patio because the things will. not. place.

The roof thing hasn't happened to me yet on a lot I remembered to flatten before I started to build on it. I don't know if that's luck or if it's the secret. Once there are buildings, flatten lot doesn't seem to entirely flatten the lot.

[Larku]

Placing columns and putting down floor tiles on the level you want the roof at can also help. I had one particular odd lot where most of the house was on diagonals that was a major pain in the ass.

I was trying the columns in hope that it would fit it, but alas it didn't. I just gave up on it for now on that house.