Also as a warning, if your sim is doing anything in one place outside, keep them away from your mailbox and garbage can. Those things WILL get scorched if a meteor hits, and are not buyable items that can be replaced, in short giving you a permanent dirty room moodlet outside unless you totally restart the lot from scratch.
I didn't come up with this, but if you change your property type to commercial, then back to residential, it can restore your mailbox and trashcan. Well, it did restore one of those for me. I had somehow managed to delete my mailbox, I think, and I asked for help on the Sims 3 forum, and I got a fix. This was before I started coming over here and before Ambitions, so it may no longer work, but if it doesn't, at least you had something to try. Of course, if you're playing in a Challenge, ask first, though this is one of those things I think might be allowed as long as you get permission before you do it.
Oh, and I'd delete the singed/scorched ones before trying the fix, if that wasn't clear. Hope this helps.