UK Cavity Tray Types & Specifications
Cavity tray DPC types, widths, weep hole spacing and installation requirements for UK cavity wall construction.
Cavity Tray Types
| Type | Application | Material | Notes |
|---|---|---|---|
| Horizontal tray | Above lintels, base of cavity | Polypropylene / lead composite | Must span full cavity width + both leaves |
| Stepped tray | Roof abutments (pitched roof to wall) | Pre-formed polypropylene | 75 mm steps to match brick coursing |
| Catchment tray | Below openings (sills) | Polypropylene | Collects water running down cavity |
| Caverntray | Ridge abutments, parapet walls | Pre-formed rigid plastic | For complex junction details |
| Perpend weep vent | Weep holes in outer leaf | Plastic insert | Max 450 mm centres along tray |
Tray Width Requirements
| Cavity Width (mm) | Min. Tray Width (mm) | Notes |
|---|---|---|
| 50 | ~300 | Must extend min. 100 mm into each leaf |
| 75 | ~325 | Standard domestic cavity |
| 100 | ~350 | Wide cavity with full-fill insulation |
| 150 | ~400 | Wide cavity with thick insulation |
Key Installation Rules
- Cavity trays must slope toward the outer leaf at a minimum fall of 1:12
- Stop ends must be fitted at each end of the tray to prevent water running off the sides
- Weep holes at maximum 450 mm centres (every other perpend in stretcher bond)
- Trays must project 5 mm beyond outer face or use weep vents
- Minimum 150 mm upstand on the inner leaf side
- Laps between tray sections: minimum 100 mm, sealed with compatible adhesive
Related Calculators
See the DPC Specifications for damp proof course types, or the UK Lintel Sizes for lintel specifications above openings.
How We Calculate This
Frequently Asked Questions
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Last updated: April 2026
All calculations are estimates. Verify with your supplier.