Sand bricks spawning critters

I have renovated my home several times, and each time that I use sand bricks, animals spawn in my house. All the doors are closed and I have a roof. Having all these animals show up gets quite annoying after a while. I have a link to a screenshot of this below. (If it's just my screwy iPod I apologize.)

https://www.dropbox.com/s/5th3wfpp4l3y5cu/screenshot.png

If you can help me I thank you greatly.

[Softkey3]

I think the animals spawn on grass, so I believe it may be a bug

[Chris]

At one point mobs were updated so that they only spawned on natural blocks.
Any crafted blocks would prevent spawning.
So, I guess Sand Bricks are still technically a natural block, hence why mobs spawn on them.
It's too bad Apple is preventing Pixbits from exporting any more updates after May 1st; otherwise, I know they would fix this if it is in fact a bug.

[Xaphos]

Probably is a bug
But nice house tho !

Damn. I'll have to renovate for the twenty-eighth time. (I hope they fix this in JJ2.) Thanks for the help guys.

WTF is that???: