What height should a DPC be above ground level?

The DPC must be at least 150 mm above finished external ground level per Approved Document C. This prevents rain splash bridging the DPC. If ground levels are raised (e.g. by paving or landscaping), the 150 mm clearance must be maintained — a common defect is paths or patios built up above DPC level, which can cause rising damp.

What width DPC do I need?

The DPC width should be at least as wide as the wall it sits in, but should not project beyond the wall face. For a standard 100 mm blockwork inner leaf, use 100 mm DPC. For a 215 mm solid wall, use 225 mm DPC. For a full cavity wall, separate DPCs are used in each leaf. Common roll widths: 100, 112.5, 150, 225, 300, 337.5, 450 and 600 mm.

Can I use engineering bricks instead of DPC?

Yes, two courses of Class A engineering bricks (DPC1 or DPC2 designation per BS EN 771-1) laid in 1:3 cement mortar can serve as a DPC. This was the traditional method before flexible DPCs and is still acceptable under Building Regulations. Engineering brick DPCs are very durable but more expensive and time-consuming than flexible DPC.

What is the difference between DPC and DPM?

DPC (damp proof course) is a horizontal barrier in walls, typically at or just above ground level. DPM (damp proof membrane) is a sheet membrane under floor slabs, typically 1200-gauge (300 micron) polyethylene. The DPM must be lapped with the DPC to form a continuous barrier. Joints in DPM should be lapped at least 150 mm and taped.

UK DPC Specifications & Placement

Damp proof course types, widths and placement rules per Approved Document C for UK building construction.

DPC Material Types

Type	Material	Thickness	Notes
Polyethylene (polythene)	High-density polyethylene	~0.5 mm	Most common modern DPC, flexible, durable
Pitch polymer	Bitumen/polymer composite	~1.5–3 mm	Self-adhesive, good on uneven surfaces
Bitumen felt	Hessian-based bitumen	~2–3 mm	Traditional type, less common now
Lead-cored	Lead sheet in bitumen	~2–3 mm	Heritage buildings, cavity trays
Engineering brick	Class A engineering bricks	2 courses (150 mm)	Traditional, very durable, labour-intensive

Standard DPC Roll Widths

Width (mm)	Typical Application
100	100 mm blockwork inner leaf
112.5	Half-brick walls (102.5 mm + overhang)
150	150 mm blockwork, cavity closers
225	One-brick walls (215 mm)
300	Cavity trays, wide walls
337.5	One-and-a-half brick walls
450	Full cavity wall (both leaves + cavity)
600	Wide cavity walls, parapet walls

DPC Placement Rules (Approved Document C)

DPC must be minimum 150 mm above finished external ground level
DPC must be continuous — laps of at least 100 mm at joints
DPC must be bedded in mortar above and below
Cavity wall: separate DPC in each leaf, linked by cavity tray at specific positions
DPC must not project beyond face of wall (to prevent water tracking inward)
DPM under floor slabs must be lapped with wall DPC to form continuous barrier
Vertical DPCs required at reveals (window and door openings)

Related Calculators

See the Cavity Tray Sizes for cavity tray specifications, or the UK Brick Dimensions for masonry coursing around DPC level.

How We Calculate This

Frequently Asked Questions

Last updated: April 2026

All calculations are estimates. Verify with your supplier.

UK DPC Specifications & Placement

DPC Material Types

Standard DPC Roll Widths

DPC Placement Rules (Approved Document C)

Related Calculators

How We Calculate This

Frequently Asked Questions

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