Sloped Greenhouse Roof Not Snapping To Wall

The triangular roof pieces work just fine.
Sloped greenhouse roof not snapping to wall. Very nice one too. A greenhouse does not need to be considered enclosed. Im trying to place a sloped roof but it keeps on snapping to the floor how do i get it to snap to the walls. Or do i need to make the walls out of wood or stronger.
I m building a greenhouse. You can build a wall up from the bottom foundations to the center of the roof tiles you re trying to place or you can try putting ceiling tiles across the center of the structure from one side of the roof. The greenhouse wall and greenhouse ceiling cost 30 engram points to unlock while all other greenhouse structures cost 15 engram points. Except the sloped greenhouse roof pieces absolutely refuse to snap to the top of the walls.
Im trying to build a roundish greenhouse and not put dividers all throughout it. It depends on which side the wall is and where you stand if the roof goes up or down. Pipes can pass through the greenhouse walls. So this looks like a support issue.
A ceiling atop pillars or snapped to an adjacent wall is sufficient. I put down greenhouse walls all around and now i just need to put on the roof. Currently only have thatch walls and im getting irritated with getting it orientated right and no matter what button i press i cant change it. Engrams for greenhouse wall and greenhouse ceiling are unlocked at level 42 greenhouse doorframe and greenhouse door at level 43 and the sloped components at level 44.
Only ramps snap to their short side not to the long side. They keep trying to snap onto the foundation or even the side of the walls but not the tops where they belong. So you cant start a sloped roof with the ceiling or floor only with a wall. Is anyone else having this issue or know a fix.
Im having an issue with the sloped greenhouse roof not snapping on top of a ceiling without being supported by a wall to the side. But not the basic. However i see 3 sloped roof tiles not supported by any wall or ceiling tile from within the structure.