Won't build second floor building

This building has been sitting there just like that for a few hours and trying everything to get them to finish it to no avail. There was a second floor underneath the roof and they refused to go any further than this, even destroyed and rebuilt to try again with same result. So is it required to have a full room before a roof? Although even after removing the second level floor they refused to go any further leaving me with this.

build a ladder at one of the corner to the top and see if anything happens.

Well, i had since made them try to remove the house and the game refuses to remove that eyesore no matter what., But I tried to recreate it again with your suggestion and it worked. Thanks.

you are welcome , you see, somehow they didnt complete the scaffolding and ladders. such things still happen from time to time. just make sure your workers can reach the place where the need to build. ladders do the trick most times.