It looks like it’s taking so long to collapse because there are so many wood pieces you have there that affect the integrity calculation so that it lags a lot.

I don’t know the contents of your house but if you have symmetrical supports so that both sides of the house receive identical structural support and only this side collapses, it’s probably an issue with your grounded support. Check the lowest layer of support (aka the first level of wood wall) and make sure they have identical support ratings (most likely they should all be blue if it is touching the ground)

The roof is all red because structural integrity is based on 2 things, strength of structure and additional integrity loss. Each structure has a max strength value and a minimum strength value that determines the maximum support it can provide when blue (connected to ground or structure with strength higher than its max) and the minimum is the minimum strength that the structure needs to not break. Additional integrity loss is a value unique to each structure material that determines the amount lost in strength to a new piece when connecting it to another piece. The roof is far away from the ground, so no matter what you do (unless you add stone walls or iron poles/beams), it will stay red. Wood poles/beams only help provide extra support if it creates a shorter path to a piece with more strength, since they follow the same strength and integrity loss rules as all wood building pieces do.