Doors and Windows
Part of Permanent Shelter
Every shelter needs openings — a door to enter, windows for light and air. But every opening is a structural wound in your wall. Understanding how to frame, support, and seal openings is the difference between a building that stands for decades and one that cracks apart in its first winter.
Why Openings Weaken Walls
A solid wall distributes its load evenly down to the foundation. Cut a hole in it and the weight above that hole has nowhere to go — it concentrates at the edges of the opening, creating stress points. In masonry and earthen walls, this concentrated load causes diagonal cracking from the corners of the opening. In timber walls, it removes structural members that were carrying roof and upper-wall weight.
The solution in every building tradition is the same: a lintel (also called a header) — a strong horizontal beam placed across the top of the opening that collects the load above and transfers it to the wall on either side.
Never Cut Openings After Building
In log, cob, and stone construction, plan your openings before you start building. Cutting holes into finished walls removes material that is already carrying load. If you must add an opening later, install temporary supports (shoring) on both sides before cutting.
Lintels and Headers
The lintel is the most critical structural element around any opening. Get it wrong and the wall above will sag, crack, or collapse.
Lintel Materials
| Material | Best For | Minimum Depth | Notes |
|---|---|---|---|
| Hardwood beam | All wall types | 15–20 cm | Oak, ash, or similar dense wood; avoid softwoods for spans over 60 cm |
| Stone slab | Stone and cob walls | 10–15 cm | Must be a single piece, not layered; granite or dense sandstone preferred |
| Split log | Log cabins | Half the log diameter | Flat side down; place bark side up to shed water |
| Brick arch | Brick and stone walls | N/A | Transfers load through compression; needs a temporary form during construction |
Lintel Sizing Rules
- The lintel must extend at least 20 cm into the wall on each side of the opening. For openings wider than 90 cm, extend 30 cm.
- For timber lintels, the depth (height) should be at least 1/10 of the span. A 1 m wide opening needs a lintel at least 10 cm deep — 15 cm is safer.
- Place the lintel with its load-bearing grain running horizontally across the opening, not vertically.
Rough Opening Sizing
The “rough opening” is the hole you leave in the wall — it is always larger than the finished door or window that will fill it. You need clearance for the frame, shimming, and seasonal wood movement.
Standard Clearances
| Opening Type | Add to Width | Add to Height | Purpose |
|---|---|---|---|
| Door | 3–5 cm total | 2–3 cm at top | Frame timber + shimming space |
| Window | 3–5 cm total | 3–5 cm total | Frame + sill drainage slope |
| In green timber walls | 5–8 cm total | 8–12 cm at top | Settling as logs dry and shrink |
Green Timber Settlement
Log walls built with unseasoned (green) timber will shrink vertically as the wood dries — sometimes 5–10 cm over the first two years. Leave a settlement gap above door and window frames and fill it loosely with moss, wool, or cloth. Do not wedge it tight or the shrinking wall will crush your frames.
Framing Openings in Different Wall Types
Log Walls
- Mark the opening on completed courses before building higher.
- Install vertical jamb posts (also called “bucks”) — these are vertical timbers nailed or pegged to the cut log ends on each side of the opening. They prevent the cut log ends from shifting.
- Cut a groove (keyway) in the back of each jamb post that slides over a tenon left on the log ends. This allows the wall to settle without binding.
- Set the lintel log across the top, resting on the jamb posts with a settlement gap above.
Stone Walls
- Build the wall up to sill height on both sides of the planned opening.
- Set vertical timber or stone jambs on each side as you continue building. In stone, you can use large squared stones for the jambs (called “quoins”).
- Lay the lintel when you reach the top of the opening. A single stone slab or hardwood beam works. For wide openings, build a stone arch using a temporary wooden form (centering).
- Continue the wall over the lintel.
Cob and Adobe Walls
- Set a wooden door or window frame directly into the wall as you build up to its height.
- Build the cob or adobe around the frame, pressing material firmly against the wood.
- Drill or embed wooden pegs into the frame sides so the cob grips the frame as it dries.
- Lay the lintel across the top — a hardwood beam works best. Extend it well into the wall mass on both sides.
Basic Door and Window Options
At the simplest level, you need something to close the opening. Options range from primitive to refined:
Doors
- Hide or woven mat — the simplest closure. Hung from a horizontal pole across the top. Stops wind, not intruders.
- Plank door — boards held together by horizontal battens (ledges) and a diagonal brace. The standard for most of human history. See Door Construction for detailed build instructions.
- Split-log door — half-logs laid side by side, held by battens. Heavier but requires less sawing.
Windows
- Open hole with shutter — a solid wooden panel hinged to cover the opening. Gives ventilation or security, not both simultaneously.
- Oiled cloth or paper — translucent panel that admits light while blocking wind. See Window Design.
- Animal membrane — scraped and stretched intestine or bladder. Translucent, surprisingly durable.
Weathersealing
An opening is only as good as its seal. Gaps around doors and windows are the primary source of heat loss and drafts.
Sealing Methods
| Method | Material | Application |
|---|---|---|
| Chinking | Clay-moss mix, lime mortar | Press into gaps between frame and wall |
| Strip seal | Leather, felt, woven cloth | Tack along door frame edges; door compresses strip when closed |
| Threshold seal | Hardwood sill, stone step | Raise the threshold 3–5 cm above floor level; add a leather flap to the door bottom |
| Drip groove | Carved channel on sill underside | Prevents water from wicking under the sill into the wall |
The Drip Groove
On any exterior window sill or door threshold, carve a shallow groove (5 mm deep) on the underside, 2 cm back from the outer edge. Water running along the underside of the sill hits this groove and drips off instead of traveling further inward. This simple detail prevents enormous water damage over time.
Security Considerations
In a rebuilding scenario, doors and windows are your primary physical security layer.
- Door thickness: A plank door should be at least 4 cm thick. Thinner doors can be kicked in easily.
- Bar locks: A heavy wooden bar dropped into brackets on both sides of the door frame is stronger than any latch. The bar should be at least 8 cm square in cross-section.
- Window size: Windows above ground level should be small enough that an adult cannot fit through — 30 cm wide maximum for security-critical openings. Place larger windows higher on the wall or on upper floors.
- Shutters: Every window needs a solid shutter that can be barred from inside. A window without a shutter is an open invitation.
- Hinge security: Hinges on the outside of a door can be pried off. Always mount hinges on the interior side, or use pintle hinges embedded in the frame.
Key Takeaways
- Every opening weakens the wall above it. A properly sized lintel transfers the load safely to the wall on each side.
- Lintels must extend at least 20 cm into the wall on each side, with a depth of 1/10 the span or more.
- Rough openings should be 3–5 cm larger than the finished frame (more in green timber walls to allow for settling).
- Frame openings as you build — do not cut holes in finished walls unless you install temporary supports first.
- Weatherseal every gap with chinking, strip seals, raised thresholds, and drip grooves.
- For security: thick doors, bar locks, small windows, solid shutters, and interior-mounted hinges.