Not sure whether you need a simple beam calculation or full structural design? This guide walks through common domestic projects and explains exactly what you'll need.
Scenario 1: Removing a Load Bearing Wall
Your project:
Opening up your ground floor by removing the wall between kitchen and living room. The wall supports the first floor and roof above.
What structural work is needed:
- Replacement beam: A steel or timber beam to carry the loads previously supported by the wall. This is typically a Universal Beam (UKB) sized to the span and loading.
- Padstones: Concrete or dense blockwork bearing pads at each end to spread the load into the masonry.
- Temporary support: Acrow props or strong boys to hold the structure while the wall is removed and the beam installed.
What Building Control want to see:
- Structural calculations showing the beam can carry the design loads (permanent + variable)
- Construction drawings showing beam size, position, padstone dimensions, and temporary works
- Specification of materials (steel grade, concrete strength)
- Proof that loads transfer safely down to foundations
What FM Structural provides:
- Standard Beam Calculation (£200-£295): For straightforward wall removals in typical construction. You get calculations, construction drawing, material specification, and temporary support details.
- If Party Wall applies: We can serve notices and handle party wall compliance (from £175)
Scenario 2: Single-Storey Extension
Your project:
Adding a 4m x 3m single-storey rear extension with a flat roof, knocking through from the existing kitchen.
What structural work is needed:
- Foundations: Typically 600mm wide strip footings to 1m depth (subject to ground conditions)
- Floor slab: 100mm concrete slab with damp proof membrane and insulation
- Walls: Cavity wall construction (brick outer, blockwork inner)
- Roof structure: Timber joists or steel beams supporting flat roof deck and weathering
- Opening beam: Steel beam where you knock through to existing house
What Building Control want to see:
- Foundation design calculations and drawings
- Floor slab specification
- Wall construction details
- Roof structural calculations and layout
- Opening beam calculations
- Thermal performance calculations (Part L compliance)
What FM Structural provides:
- Full Structural Design Package (£450-£650): Complete calculations and drawings covering foundations, floor slab, walls, roof structure, and opening beam. Suitable for Full Plans Building Regulations application.
- If ground conditions are poor or unknown, we can recommend a soil investigation and design foundations accordingly.
Scenario 3: Loft Conversion
Your project:
Converting your trussed-rafter roof space into a bedroom and en-suite. You'll need to remove some of the existing trusses and create headroom.
What structural work is needed:
- Roof alterations: Steel beams to replace the structural function of removed truss members. This often involves a ridge beam and supporting posts down to load-bearing walls.
- Floor strengthening: Existing ceiling joists (typically 100×50mm) are not designed as floor joists. You'll need to double them up, add new joists, or install steel beams.
- Staircase opening: Trimmer joists and possibly a steel beam to create the stair void.
- Dormer (if applicable): Structural frame for dormer window, including lintel over opening and valley beams.
What Building Control want to see:
- Roof alteration calculations and layout drawings
- Floor joist calculations (with deflection checks for vibration)
- Staircase opening structural details
- Dormer frame calculations (if applicable)
- Load paths showing how loads transfer to existing structure and foundations
What FM Structural provides:
- Full Structural Design Package (£550-£850): Comprehensive calculations and drawings for roof alterations, floor strengthening, staircase opening, and dormer (if applicable). Includes review of existing structure and recommendations for strengthening.
- If the existing structure shows signs of movement or distress, we can carry out a structural survey to identify issues before you commit to the conversion.
Scenario 4: Two-Storey Extension
Your project:
Adding a two-storey side extension, extending kitchen on ground floor and adding a bedroom above.
What structural work is needed:
- Foundations: Deeper and wider than single-storey due to higher loading
- Ground floor slab
- Ground floor walls: Designed to carry first floor + roof loads
- First floor structure: Timber joists or beam-and-block floor
- First floor walls
- Roof structure: Pitched roof tied into existing roof, or independent structure
- Opening beams: Where you knock through at ground and first floor levels
What Building Control want to see:
- Complete structural package from foundations to roof
- Calculations for all load-bearing elements
- Construction drawings showing floor plans, sections, and critical details
- Integration details showing how new structure ties into existing
What FM Structural provides:
- Full Structural Design Package (£750-£1,200): Comprehensive calculations and drawings for the entire extension, including foundations, floors, walls, roof, and opening beams. Includes details for tying new work into existing structure.
- We can coordinate with your architect to ensure structural design aligns with architectural intent.
Scenario 5: Just Need a Padstone Calculation
Your project:
Building Control has asked for padstone calculations for an existing beam that's already installed, or your builder needs confirmation of padstone size before ordering materials.
What FM Structural provides:
- Padstone Calculation (£95-£150): Quick turnaround calculation showing padstone dimensions, bearing length, and reinforcement if needed. Suitable for retrospective Building Control submission or pre-construction confirmation.
Scenario 6: Party Wall Act Compliance
Your project:
Any of the above scenarios, but the work affects a shared wall with your neighbor, or you're excavating within 3 meters of their property.
What the Party Wall Act requires:
- Written notice served on adjoining owners at least two months before starting work
- Description of the proposed work
- Drawings showing what you're doing
- If your neighbor dissents (or doesn't respond), surveyors are appointed to agree a Party Wall Award
What FM Structural provides:
- Party Wall Notice Service (£175-£300): We prepare and serve the required notices on your behalf, including drawings and descriptions.
- Party Wall Surveying (from £800): If a dispute arises, we can act as the Building Owner's surveyor to negotiate the Award.
- Party Wall services are often bundled with structural design - if you need both, we offer a package rate.
Quick Decision Guide
Choose Standard Beam Calculation if:
- You're removing a single wall in typical construction (cavity wall, timber floor, standard roof)
- The span is straightforward (under 4.5m)
- No complications (no existing movement, ground is stable, construction type is known)
Choose Full Structural Design if:
- You're building an extension (any size)
- You're doing a loft conversion
- You're removing multiple walls or creating a large opening (>4.5m)
- The property is non-standard (timber frame, pre-1919, listed building)
- There are complications (existing cracks, unknown foundations, poor ground)
Add Party Wall services if:
- You're working on a shared wall
- You're excavating within 3m of your neighbor's structure
- You're building a new wall on the boundary
Still Not Sure?
Submit an enquiry with photos and a description of what you're doing. We'll review it and recommend the appropriate service level. If you've selected a higher service tier than necessary, we'll tell you - we don't upsell.
You can also use our template gallery to identify your project type and get an instant indication of what's typically needed.