FSX-MS Rooftop helipads not landable

[morgy2810 0]

I've been flying around the lax area recently,i have tried to land on the rooftop helipads of the building.the helipads are clearly marked out but i just sink right through them,one more thing,does anybody know any livarys for fsx from the programme '24'? any help is appreciated!

[Tatave 57]

Sometimes, buildings in FSX aren't 'solid' (saves processing power). Some helipads may be marked, but not solid. There are many others, however, which are solid objects and 'landable'. 

[morgy2810 0]

Sometimes, buildings in FSX aren't 'solid' (saves processing power). Some helipads may be marked, but not solid. There are many others, however, which are solid objects and 'landable'. 

ok thanks for the info,shame about that.seems its all the high building (which i want to work most) that i fall through and the small building that have solid roofs!