This, And The Other "Build Structure With X Logs" Achievements, Were Replaced With "Place X Logs" Achievements.
Place 50 Logs And The Achievement Is Yours.
1) You Can Place Down One Log.
2) Then "Mouse Click" To Put Another On Top.
3) Then Hold "C" To Pick Up The Second Log.
Then Repeat Steps 2-3 Until You Get This Achievement.
Good Luck!