Does a porch need Building Regulations approval?

If the porch is at ground level, has a floor area of 3m² or less and is no higher than 3m, it is generally exempt from Building Regulations. Over 3m² or over 3m high, full Building Regulations apply including Part L insulation, Part B fire safety and structural requirements. All porches need to comply with planning requirements.

Does a porch need planning permission?

A porch is usually permitted development if: the floor area is 3m² or less, it is no higher than 3m above ground level, and no part is within 2m of a boundary fronting a highway. In conservation areas, Article 4 directions or on listed buildings, planning permission may be needed regardless of size.

What foundation does a porch need?

A porch typically needs a strip foundation 450mm deep and 450mm wide around the perimeter. On clay soils or near trees, deeper foundations may be needed. For small porches under 3m², some local authorities accept a concrete pad or slab foundation without deep strip footings.

Does a porch need insulation?

If the porch is exempt (under 3m²), no insulation is required by Building Regulations. If over 3m², Part L applies and walls need U-value 0.26, floor 0.22, roof 0.15. If you remove the original front door, making the porch part of the house, all porch elements must be insulated to Part L standards regardless of size.

How much does a porch cost to build?

A small brick porch (under 3m²) typically costs £3,000–£6,000. A larger porch (3–6m²) requiring Building Regulations costs £5,000–£12,000 depending on specification. Full brick walls cost more than dwarf wall with glazing. Costs vary by region and finish quality.

TradeCalculator

Porch Calculator — Foundations, Structure & PD Limits

Calculate porch material quantities and determine whether the porch is exempt from Building Regulations (under 3m²) or requires a full application.

Porch length

Porch width (depth)

Porch height

Roof type

Wall type

Include front door

How We Calculate This

This calculator determines porch material quantities and checks Building Regulations exemption status.

Exemption check

Porches at ground level, under 3m² floor area and under 3m height are exempt from Building Regulations. Over 3m² triggers full compliance with Part L, B, P and structural requirements.

Material quantities

Foundation concrete, brickwork and roof area are calculated from the porch dimensions, wall type and roof type.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.