I just remember the song from the Commodores...Built like a brick house...meaning well-stacked...I only remember it because I think the song came out the year I was roomies with a girl that guys would sing that out to her when she walked by...yeah...that was awkward...

Ow, she's a brick house
She's mighty-mighty, just lettin' it all hang out
She's a brick house
That lady's stacked and that's a fact
Ain't holding nothing back

@btroje, @Sheanutt
I grew up with the saying, “she’s built like a brick outhouse”. It always meant she had a sexy body, but it always left a question in my head. After thinking about it (too much) I believe the outhouse represents people. We all go to the toilet. Built or stacked like a brick outhouse just means one’s fit.

And after further deliberation in my head (more wasted time) I came to another conclusion, all brought on by a conversation I had with my mom on the way home from her exercise class.

As @firecracker commented, outhouses are normally built from wood and not necessarily built well. So a brick outhouse might be well built but it’s just for show. There’s no good reason for it.

The first photo is a house just up the street from us. My dad used to call it the outhouse. Perhaps you’ll understand why. The 2nd photo is a new house they’re building about 3 blocks away. Mom said something about it looking like a fancy outhouse. I added the bricks and away we went.

That’s my story and I’m sticking to it.

The version of this "compliment" that I have heard is, "She's built like a brick shithouse!"

According to this analysis, the statement was probably originally used in a smart-assed sort of context, but over time it became generally intended as complimentary. After all, old-time shithouses aren't known to be particularly sturdy structures, but if one is made of brick then it would be the sturdiest shithouse around!! lol

If it's intended as a compliment when spoken, then the thing to do is to take it as such.

[straightdope.com]

that has always confused me