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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)
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See the Cavity Tray Sizes for cavity tray specifications, or the UK Brick Dimensions for masonry coursing around DPC level.
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Frequently Asked Questions
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.
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.
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.
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.
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Last updated: April 2026
Verified against UK standards · estimates only, confirm with your supplier.