A door is only as strong as its frame, hinges and the point where the bar or lock bears on the wall, so hardening starts there and not with a thicker door leaf. Boards over a window with wide gaps screen and delay but do not stop a thrown or pushed object, and a sandbag stack on an upper-floor sill can load the floor to roughly ten times what it was designed for. Every occupied room must keep one exit that opens from inside.
Window and door hardening is the strengthening of the openings in a building’s wall, the places where an intruder or a thrown object reaches the inside.
Where Doors And Windows Actually Fail
The parent article recommends boarding windows with planks 2 cm thick and gaps of 10 cm, sandbags on the sills, wire mesh outside, a door bar in brackets, sandbags behind the door and a second barrier 2 to 3 m inside. Each has a limit.
- Door leaf versus frame. The leaf is usually not the weak part. The frame can split, the hinge screws can pull out of the frame, and the bar’s brackets can tear off the trim. Strengthen the fixings into the structural wall: long screws or through-bolts that reach the framing or masonry, not the trim.
- Hinges. An outward-opening door has its hinge pins exposed on the outside; they can be driven out unless pinned or peened. Inward-opening doors put the load on the strike side. See Door Construction for bracing a door correctly (the direction of the diagonal matters) and Doors and Windows for why the opening needs a lintel.
- The bar. The parent article is right that a bar spreads force across the whole frame, but only if its brackets are fixed into the structure. A bar in brackets screwed to trim fails with the trim.
- Boards. A plank 2 cm thick at an assumed 500 kg/m³ is 0.02 x 500 = 10 kg/m² of wall face. That screens and slows; it does not resist a push or a thrown stone like a masonry wall. A gap of 10 cm is wide enough to pass a forearm to reach the fixings or the latch; a gap narrower than a hand reduces that. I could not source the 10 cm figure as the right gap, and the best width is a judgement between ventilation, view and reach.
- Mesh. Heavy mesh outside keeps out thrown objects while passing light and air (parent article), but only if it is fixed to the frame with fixings that cannot be removed from outside.
- Glass. Broken glass is a hazard to the people inside; fit shutters inside the glass or remove the glass behind the mesh. See Window Design for the alternatives to glass.
Method: Harden An Opening In Order
Step 1: Fix the frame to the wall. Check the frame is anchored to the structure; replace short screws with fixings that reach the framing or masonry. For earthbag or masonry walls see Window and Door Framing in Earthbag Walls.
Step 2: Deal with the hinges and the strike. Pin or peen outward-facing hinge pins. Reinforce the strike side of an inward-opening door with a metal plate or a thick timber backing fixed through to the structure.
Step 3: Add the bar, fixed into the structure. A drop bar in brackets fixed through the frame into the wall. Make it removable from the inside by one person.
Step 4: Shutter the windows from inside. Interior shutters (thick wood, barred inside) can be closed quickly and do not hide the mesh or glass behind them. Leave one window per room that opens from inside without tools.
Step 5: Add a screening space, not a trap. The parent article suggests a second barrier 2 to 3 m inside the door. Treat that as a place where a visitor waits to be recognised before the inner door opens. Both doors must open from the inside, and nobody may be locked into the space: a person confined in a small room is a hostage, not a deterrent, and it is a fire death if the building burns.
Worked Example: Will The Floor Take The Sandbags?
The parent article stacks sandbags on inside sills to chest height. Take a stack 1.2 m high and 0.4 m thick at an assumed 1,600 kg/m³ per metre of window width:
- Mass: 0.4 x 1.2 x 1,600 = 768 kg per metre.
- Force: 768 x 9.81 = 7,534 N = 7.5 kN.
- Spread over a strip 0.4 m wide: 7.5 / 0.4 = 18.8 kN/m².
- A residential floor is designed for a live load of about 1.9 kN/m² (40 lb/ft²; a recalled figure from US building loads, not sourced in this corpus; find your own).
- Ratio: 18.8 / 1.9 = 9.9, about ten times.
On a floor on the ground, or a concrete slab, this is fine. On a timber upper floor it is not. Laying the bags on planks 1.2 m wide spreads 7.5 kN over 1.2 m, which is 6.3 kN/m², still more than three times the design load. A stack half as high halves the figures. Check the structure before building, or keep heavy stacks on the ground floor. See Earth Load Calculations for converting soil weight to force.
Common Mistakes
- Reinforcing the door leaf and leaving the frame. The frame fails first.
- Fixings into trim. A bar on trim is decoration.
- Boards with wide gaps. They do not stop a thrown object or a hand.
- Sandbags on an upper floor. Check the floor first.
- No window that opens from inside. It is the escape route when the door is blocked or burning.
Safety
A hardened opening must still open from the inside
Every sleeping room needs one window or door that opens from inside without a key, tool or force. Bars, shutters and mesh over every opening have killed occupants in fires. A stack of sandbags can collapse a floor, and the added mass is dangerous to anyone below it. Do not barricade an occupied room in a way that one person cannot undo from inside.
What’s Next
- Learn next: Interior Barriers — the room behind the opening
- Combine with: Escape Route Planning — keeping a way out