Safe Load Tables for RSJ Beams Over Openings (Doors, Windows, Garages) – 2026 Updated
When installing RSJ beams over openings such as doors, windows, or garage doors, determining the safe load is critical for structural integrity and Building Regulations compliance. This guide provides quick-reference safe load tables specifically for common opening scenarios in residential and light commercial construction.
Understanding Loads Over Openings
What Loads Does the Beam Carry?
An RSJ beam over an opening must support:
1. Self-weight of beam 2. Dead loads above:
- Masonry (bricks/blocks directly above beam)
- Floor construction (joists, boards, plaster)
- Partition walls
- Roof structure and covering (if applicable)
3. Live loads:
- Occupancy loads (people, furniture)
- Snow loads (for roofs)
- Wind loads (usually less critical)
Load Triangle Concept
For masonry above an opening, loads typically distribute in a 45-degree triangle pattern:
- Load height ≈ Half the span width
- Example: 4m wide opening, load triangle extends ~2m above beam
- Arch action in masonry means not all weight above transfers to beam
However, Building Regulations require conservative assumptions:
- Design load width = Full span
- Design load height = As calculated per structural principles
Safe Load Tables by Opening Type
Single Pal Doors (900-1050mm wide)
Typical scenario: Internal wall removal, single door remaining
| Beam Size | Max Safe Load (kN/m) | Typical Use | Max Span |
|---|---|---|---|
| 152×127×37 | 12 | Single story | 2.5m |
| 178×102×19 | 8 | Lightweight partition | 2.0m |
| 203×133×25 | 18 | Standard residential | 3.0m |
Example Calculation (900mm door):
- Span: 1.2m (900mm + bearing each side)
- Load above: Half-brick wall (2m high) + bedroom floor
- Masonry: 0.5m wide × 2m high × 2.3 kN/m³ = 2.3 kN/m
- Floor load: 3.5 kN/m² × 1.5m width = 5.25 kN/m
- Total: ~7.5 kN/m
Beam selection: 152×127×37 RSJ adequate (12 kN/m capacity > 7.5 kN/m) ✓
Double Doors / French Doors (1800-2400mm)
| Beam Size | Max Safe Load (kN/m) | Typical Use | Max Span |
|---|---|---|---|
| 152×127×37 | 10 | Light loads only | 2.5m |
| 203×133×25 | 15 | Standard residential | 3.0m |
| 203×133×30 | 18 | Heavier loads | 3.2m |
| 254×146×31 | 22 | Two-story loads | 3.5m |
Example (2.1m French doors to garden):
- Span: 2.5m
- External cavity wall above (2.5m high)
- Bedroom floor above
- Masonry: Full cavity wall × 2.5m = 6.5 kN/m
- Floor: 3.5 kN/m² × 2.5m = 8.75 kN/m
- Total: ~15.3 kN/m
Beam selection: 203×133×30 RSJ (18 kN/m > 15.3 kN/m) ✓
Large Windows (2-3m wide)
| Beam Size | Max Safe Load (kN/m) | Typical Use | Max Span |
|---|---|---|---|
| 203×133×25 | 12 | Single story | 3.5m |
| 203×133×30 | 15 | Standard two-story | 4.0m |
| 254×146×31 | 20 | Heavy masonry | 4.5m |
| 254×146×37 | 24 | Multiple floors | 5.0m |
Example (2.4m bay window):
- Span: 2.8m
- Brickwork triangle + floor + roof
- Masonry load: ~4.5 kN/m
- Floor load: 7.0 kN/m
- Roof load: 2.5 kN/m
- Total: ~14 kN/m
Beam selection: 203×133×30 RSJ (15 kN/m > 14 kN/m) ✓
Knockthroughs (3-5m openings)
Common scenario: Combining living and dining rooms
| Beam Size | Max Safe Load (kN/m) | Typical Span | Load Type |
|---|---|---|---|
| 203×133×25 | 6.5 | 3.5m | Light (partition above) |
| 203×133×30 | 8 | 4.0m | Medium (floor above) |
| 254×146×31 | 10 | 5.0m | Medium-heavy |
| 254×146×37 | 12 | 5.5m | Heavy (two floors) |
| 305×165×40 | 15 | 6.5m | Very heavy |
Example (4m knockthrough):
- Span: 4.3m (4m opening + bearing)
- Bedroom above (floor joists 2.5m span rest on beam)
- Dead load: 0.50 kN/m²
- Live load: 1.5 kN/m²
- Floor UDL: (0.5 + 1.5) × 2.5 = 5.0 kN/m
- Beam self-weight: ~0.3 kN/m
- Total: ~5.3 kN/m
Beam selection: 203×133×30 RSJ (8 kN/m capacity at 4m span) ✓ with good safety margin
Single Garage Doors (2.4-3m wide)
| Beam Size | Max Safe Load (kN/m) | Max Span | Typical Use |
|---|---|---|---|
| 203×133×25 | 8 | 3.0m | Garage only (no room above) |
| 203×133×30 | 10 | 3.2m | Light storage above |
| 254×146×31 | 14 | 3.5m | Bedroom above (timber floor) |
| 254×146×37 | 17 | 4.0m | Heavy load above |
| 254×146×43 | 20 | 4.5m | Concrete floor above |
Example (2.5m garage with room above):
- Span: 2.8m
- Timber floor + plasterboard ceiling above garage
- Dead load (floor etc.): 1.2 kN/m²
- Live load (bedroom): 1.5 kN/m²
- Load width: 4.5m (depth of garage) -UDL: (1.2 + 1.5) × 4.5 = 12.15 kN/m
- Total: ~12.2 kN/m
Beam selection: 254×146×31 RSJ (14 kN/m > 12.2 kN/m) ✓
Double Garage Doors (4.5-6m wide)
| Beam Size | Max Safe Load (kN/m) | Max Span | Typical Use |
|---|---|---|---|
| 254×146×31 | 8 | 5.0m | Garage only |
| 254×146×37 | 10 | 5.5m | Light load above |
| 254×146×43 | 12 | 5.5m | Medium load |
| 305×165×40 | 15 | 6.5m | Standard residential |
| 305×165×46 | 18 | 6.8m | Heavy loads |
| 305×165×54 | 21 | 7.2m | Very heavy |
Example (5m double garage, bedroom above):
- Span: 5.3m
- Timber floor construction
- Load width: 5.5m
- Loads: 2.7 kN/m² total
- UDL: 2.7 × 5.5 = 14.85 kN/m
- Total: ~15 kN/m
Beam selection: 305×165×40 UB (15 kN/m capacity at 6.5m, works for 5.3m) ✓
Patio Doors (2.4-4.2m wide)
| Beam Size | Max Safe Load (kN/m) | Max Span | Wall Type |
|---|---|---|---|
| 203×133×25 | 12 | 3.2m | Single story |
| 203×133×30 | 15 | 3.8m | Two-story (timber floor) |
| 254×146×31 | 18 | 4.5m | Two-story (heavier load) |
| 254×146×37 | 21 | 5.0m | Multiple floors |
Example (3.6m bi-fold doors):
- Span: 4.0m
- External cavity wall + floor + roof above
- Masonry: ~5.5 kN/m
- Floor: ~7.0 kN/m
- Roof: ~3.0 kN/m
- Total: ~15.5 kN/m
Beam selection: 254×146×31 RSJ (18 kN/m > 15.5 kN/m) ✓
Critical Design Factors for Openings
1. Bearing Requirements
All calculations assume adequate bearing:
- Minimum: 100mm bearingeach end
- Preferred: 150mm bearing
- On padstones: Properly sized concrete bearings distributing load to masonry
Without proper bearing, beam capacity significantly reduced!
2. Lintel vs. Beam Confusion
Lintels (pre-cast concrete or steel):
- Designed for masonry loads only
- Typically 0.6-1.5 kN/m capacity
- NOT suitable for floor loads
Beams (RSJ/UB):
- Designed for masonry + floor/roof loads
- 5-25+ kN/m capacity
- Required when floors/roofs rest on opening
Never substitute a lintel where a beam is specified!
3. Load Width Determination
How far do loads extend to either side of beam?
Floor joists parallel to beam: Load width = joist span Floor joists perpendicular: Load width = spacing between other supports No joists (solid floor): Typically 60% of room depth as load width
Always verify with structural engineer’s drawings
4. Wall Type Impact
Single-leaf brick wall:
- ~2.3 kN/m² (per m height)
Cavity wall:
- ~3.2 kN/m² (per m height)
Timber frame with brick facing:
- ~1.5 kN/m² (per m height)
- Much lighter than solid masonry
Concrete block:
- ~1.9 kN/m² (per m height, standard blocks)
- ~2.8 kN/m² (dense blocks)
5. Multiple Openings in Same Wall
Two openings close together:
- Pier between openings carries load from both
- May need heavier beams or strengthen pier
- Structural engineer must assess combined effect
Example risk scenario:
- Two 2m openings separated by 600mm pier
- Each beam designed for its own load
- Pier crushes because it supports both beams concentration
- Solution: Heavier pier (engineering bricks) or continuous beam across both openings
Safety Margins in Tables
All table values include safety factors:
Material safety factor: 1.0-1.1 (steel is consistent material) Load safety factors:
- Dead loads: ×1.35
- Live loads: ×1.5
Deflection limits: span/360 (floors) or span/200 (roofs)
Typical overall safety factor: 1.5-2.0 on actual expected loads
This means: Even if your calculated load matches table value, there’s still safety margin. However, never intentionally overload beyond table values.
When Tables Are Not Sufficient
Consult structural engineerwhen:
- Spans exceed table maximums
- Loads higher than shown
- Unusual geometry (angled walls, curved openings)
- Existing structure is non-standard (very old buildings, unconventional construction)
- Multiple beams interact (beams supporting other beams)
- Building Control requires (always for significant alterations)
- Point loads above opening (internal walls, columns, concentrated loads)
- Weak foundations (settlement risk, poor ground conditions)
Cost of engineer: £350-650 for typical domestic project Cost of failure: £10,000+ for remedial works
Always worth getting professional advice!
Real-World Examples with Beam Selection
Example 1: Victorian Terrace Knockthrough
Scenario:
- Remove wall between living room and dining room
- 3.8m wide opening
- Original house (solid brick walls)
- Bedroom directly above
- Floor joists 3.5m long, rest mid-span on removed wall location
Loads:
- Solid brick wall above (assume 1.9m average height): 1.9 × 2.3 = 4.4 kN/m
- Floor structure dead load: 0.6 kN/m² × 1.75m = 1.05 kN/m
- Floor live load: 1.5 kN/m² × 1.75m = 2.63 kN/m
- Total UDL: ~8.1 kN/m
Beam length required: 3.8m + 0.3m = 4.1m
From tables: 203×133×30 at 4.0m span, 8 kN/m capacity
Slightly over span (4.1m vs 4.0m max), so check next size: 254×146×31 at 5.0m span, 10 kN/m capacity ✓
Selection: 254×146×31 RSJ, length 4.1m Cost: ~£310 for beam + structural engineer + Building Control
Example 2: New Build Garage
Scenario:
- 5.2m wide double garage door
- Master bedroom above (timber frame floor)
- External cavity wall construction
Loads:
- Cavity wall (2.4m high): 2.4 × 3.2 = 7.7 kN/m
- Timber floor dead load: 0.8 kN/m² × 5.0m = 4.0 kN/m
- Bedroom live load: 1.5 kN/m² × 5.0m = 7.5 kN/m
- Total UDL: ~19.2 kN/m
From tables: Double garage, 5.2m span, ~19 kN/m load → Need 305×165×46 UB
Check: 305×165×46 UB has capacity ~18 kN/m at 6.8m span, so at 5.2m span has higher capacity ✓
Alternative consideration: 305×165×40 UB might work (15 kN/m at 6.5m), but load (19.2) exceeds this Must use 305×165×46 UB or larger
Selection: 305×165×46 UB, length 5.5m Cost: ~£425 for beam
Example 3: Extension with Multi-Story Load
Scenario:
- 4.5m wide opening for extension connection
- Ground floor room below
- First floor bedroom
- Roof above
- External walls transferring all loads to beam
Loads:
- Masonry (3.5m total height across 2 floors): ~10 kN/m
- First floor: 3.5 kN/m² × 3.0m width = 10.5 kN/m
- Roof: 2.5 kN/m² × 3.0m width = 7.5 kN/m
- Total UDL: ~28 kN/m (very heavy!)
This exceeds most residential table values!
Solution requires engineering calculation, but estimation: Need very heavy beam, possibly:
- 305×165×54 UB (capable of ~21 kN/m at 7.2m span, so at 4.5m might handle ~32 kN/m) ✓
- Or 356×171×45 UB
- Or intermediate support (column) to split span
Critical: This level of loading absolutely requires full structural engineering
Selection: Determined by structural engineer with full load analysis Likely beam: 305×165×54 UB or larger Cost: £550-700 for beam alone
Conclusion
These safe load tables provide quick reference for common opening scenarios in residential construction. Use them for initial feasibility assessment, but always engage a chartered structural engineer for final design verification and Building Regulations compliance.
Key Principles:
- Determine your opening type and span
- Calculate or estimate total UDL on beam
- Find beam size with adequate capacity in tables
- Add safety margin (choose one size up if close to limit)
- Verify with structural engineer
- Obtain Building Control approval before work
Remember: Tables show safe loads under typical conditions. Unusual situations, very old buildings, or loads near table limits require professional engineering assessment.
Disclaimer: Tables provided for preliminary guidance only. All structural work must be designed by a chartered structural engineer and approved by Building Control. These tables do not replace professional engineering calculations or Building Regulations compliance.
