Wood door hardening is reinforcing various parts and components of the door, including installing additional hardware, to ensure immunity to kick-ins and decrease susceptibility to a variety of other break-in methods.
For wood doors we recommend installing solid-core doors with 18" or larger strike plates, a minimum of three hinges that are 4" x 4" or larger, 3.5" #9 screws for the strike plate and hinges, a full door length latch guards, a grade 1 deadbolt, and a grade 1 door closer.
We recommend installing solid-core wood doors.
The solid core wood doors are stronger than hollow core doors. They are, actually, stronger than most residential grade sheet metal doors.
Grade 1 dead bolts are designed and tested (by BHMA) to with stand significantly more powerful blows (meaning kicks or blows from a sledge hammer) than a grade 2 or grade 3 deadbolt. a grade 1 deadbolt has to withstand 2 blows at 60lbf, 2 at 90lbs and 2 at 120lbs, where as a grade 3 only needs to withstand 2 blows at 60lbf. Also, the bolt is tested to 1200 lbf of pushing force as opposed to only 600 lbf.
These hinges allow for 3.5" #9 screws to attach through the jamb and into the framing studs at three point along the height of the door. This greatly increases the kick and pry resistance of the door.
A full length latch guard covers the gap from the top of the door to the bottom and makes it very difficult to pry open the door, even with a 36" crowbar. The quality of the latchguard is very important. Short 12" ones are very ineffective.
The 3.5" #9 screws are long enough to pass through the hinge plates or strike plate, through the jamb trim and into the 2"x4" studs that frame the opening. by screwing into the studs the kick resistance of the door is greatly increased.
Consistent, effective closing and latching is the purpose of a closer. Grade 1 closers meet ADA requirements for door opening resistance pressure while still providing for consistent closings. Grade 2 closers do not meet the stands consistently.
We use 18" tall strikes with 3.5" hardened #9 deck screws to spread the force of some one kicking or prying the door over 18 inches of the jamb instead of 2 inches. This makes the strike plate on the jamb stronger than most doors and eliminates it as the "weakest link" in the door opening.