#Proper Leadwork (2026): Upstands & Drips—Heights, Throatings & Edge Geometry
Welcome to the New Year master guide on lead upstands and drips. Rather than chase every edge case, this article concentrates on the dimensions and shapes that keep water out and façades clean. Along the way, you’ll find precise height ranges, clear rules for throatings and radii, and step-by-step workflows for aprons, parapets, gutters, and valleys. Finally, every section links to The Lead Lads® store and standards so you can specify, price, and order with confidence.
Copper & Stainless Fixings
Low-Friction Lead Underlay
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The Lead Lads: Services & Prices
Lead Lads Standards Hub
GNR Roofing: Leadwork Authority
Regulatory Standards (BS 6915)
Part 10 of our “Proper Leadwork: Technical Series”. It consolidates Parts 3–9 into one, edge-focused playbook.
1) Why edges rule: the water path in 3 moves
First, water must rise and separate—your upstand and its chase enable that. Next, runoff needs a controlled leap—your drip provides the projection and radius. Finally, the flow must fall away cleanly—your throating breaks surface tension. When these three elements work as a set, leaks and stains become rare outliers.
- Upstand: Adds height so wind or splash cannot force water over.
- Drip: Throws runoff clear of adjacent surfaces and joints.
- Throating: Interrupts tracking beneath noses and cills.
2) Upstand heights by detail & exposure
Start with measurable targets; then adjust for exposure and visibility. The ranges below balance protection, proportion, and movement.
| Detail | Urban/Normal Exposure | Severe/Coastal Exposure | Notes |
|---|---|---|---|
| Chimney aprons & side flashings | 75–120 mm | 100–150 mm | Increase where wind-driven rain persists |
| Parapet & cornice cappings | 75–120 mm back upstand | 100–150 mm | Keep drips visible both sides on copings |
| Back gutters (chimneys) | ≥ 75 mm returns & saddles | ≥ 100 mm | Pair with ≥ 1:80 fall and a safe overflow |
| Valley margins to walls | 90–120 mm | 110–150 mm | Protect against splash and scour at mitres |
Although bigger can look safer, excessive height often traps render and invites cracking. Aim for “enough, not too much”.
3) Drip geometry: projection, radius & consistency
A clean drip seems simple; however, its geometry carries the load. Use these ranges as your default; then refine for exposure and view lines.
| Edge | Projection | Radius/Shape | Notes |
|---|---|---|---|
| Chimney apron nose | 20–25 mm | Smooth, even radius | Throw water clear of slate/tile noses |
| Parapet capping edges | 20–25 mm (each side) | Soft radius—no sharp creases | Keep the line straight along the run |
| Cill & string course covers | 15–20 mm | Crisp arris with throating | Staining disappears when throated correctly |
| Valley discharge lips | Case-by-case | Rounded edge | Prevent scouring and splash-back |
More importantly, maintain consistency. A wavy nose often means tight clips or a rough substrate—fix both before handover.
4) Throatings: undercuts that stop staining
Without a throating, surface tension drags water back under the nose. Consequently façades stain and joints remain damp. Cut a discreet under-groove beneath parapet, cornice, and cill noses so drops fall free.
- Depth: A visible notch of several millimetres breaks tracking reliably.
- Continuity: Carry the throating across joints uninterrupted.
- Coordination: Keep noses proud of render; do not bury the groove.
5) Choosing codes for edges (aprons, parapets, gutters)
Edges take knocks, wind, and thermal cycling. Therefore select codes that hold shape yet still move.
| Edge Type | Typical Code | Why |
|---|---|---|
| Chimney aprons & cover flashings | Code 4–5 | Forms tidy noses while accommodating movement |
| Parapet & cornice cappings | Code 5–6 (7 in exposure) | Stiffer edges for straighter drips |
| Back & parapet gutters | Code 5–7 | Capacity, debris resistance, and occasional footfall |
| Valley margins | Code 6–7 | Scour-resistant in high-energy zones |
6) Welts, seams & capillary control
Wind can drive water uphill. In response, welts stiffen edges and defeat capillary creep. Nevertheless, do not let a welt trap movement.
- Side laps: 60–75 mm; add a welt where exposure is severe.
- Long façade edges: Welt to sharpen the line and arrest tracking.
- Valley and mitre turns: Radius transitions to avoid crack-starter corners.
Geometry wins. Use sealant only as flexible pointing, never as a structural substitute for a welt.
7) Interfaces: soakers, flashings, rolls & gutters
Interfaces decide whether edges succeed. Coordinate adjacent parts so each helps the next and nothing fights movement.
| Interface | Edge Rule | Why it Works |
|---|---|---|
| Soakers + step flashing | Upstand 75–120 mm; chase ~25 mm; drip consistent | Two-layer defence with serviceable steps |
| Cover flashing over render | Continuous drip; clips 300–450 mm; laps unpinned | Fast straight line that still slides |
| Hollow/wood rolls into parapet | Welt long edges; soften end radii | Movement control with clean visual caps |
| Parapet/box gutter edges | Drip both sides; ≥1:80 fall; explicit overflow | Water exits quickly and safely during storms |
8) Thermal movement at edges: clips, straps & spacing
Metal moves daily; edges show it first. Consequently, restrain uplift yet allow sheets to slide along their length.
| Location | Fixing | Typical Centres | Notes |
|---|---|---|---|
| Apron noses & side flashings | Clips (Cu/SS) | 300–450 mm | Keep lap zones free of fixings |
| Parapet/box gutter edges | Straps + clips | 300–400 mm | Tighten centres in severe exposure |
| Roll edges & drips | Clips | 300–400 mm | Maintain an even nose line |
Should ripples appear at a nose, either clips are too tight or the deck is rough. Loosen spacing and smooth the substrate.
9) Substrates: brick, stone, render & coping stones
Edges rely on their base. Therefore cut clean chases, repair friable masonry, and keep render clear of drips and throatings.
- Brick: Even chase depth (~25 mm); point with compatible mortar or neutral-cure sealant.
- Stone: Test discreetly; protect arrises; avoid spalls while cutting.
- Render: Keep noses proud; never bury the drip or throating.
- Coping stones: Provide drips both sides; step joints over coping joints.
10) 10-step edge workflow (apron, parapet & valley)
- Survey: Record exposure, substrate soundness, and drainage routes.
- Choose code: 4–6 for aprons/cappings; 6–7 for valleys/gutters.
- Set upstands: 75–150 mm by detail/exposure; mark a physical datum.
- Design drips: 20–25 mm projection (15–20 mm on cills) with smooth radii.
- Add throatings: Continuous undercut beneath noses; verify visibility.
- Lay out laps: Head 100–150 mm; side 60–75 mm; no fixings in lap zones.
- Fixings: Clips/straps at 300–450 mm; tighten spacing in exposure.
- Underlay & deck: Smooth deck plus low-friction underlay to reduce abrasion and noise.
- Form radii: Soften corners; avoid crack-starter creases.
- QA & handover: Photograph datum, drips, throatings, corners, and overflow features.
11) Worked examples (3 scenarios)
Example A: New apron to brick chimney (urban, 35° slate)
- Upstand: 100 mm; chase ~25 mm; neat pointing for a tidy reveal.
- Drip: 22 mm smooth radius over slate noses for clean throw.
- Code: 4–5; clips @ ~350 mm; laps unpinned for movement.
- Outcome: Clean façade, strong reveal, quiet thermal slide.
Example B: Parapet capping on exposed seafront
- Upstand: 120–150 mm back upstand; drips both sides for balance.
- Drips: 25 mm with continuous throating to break tracking.
- Code: 6–7; straps @ 300–350 mm; welted long edges.
- Overflow: Weir/spout to the external face for safe failure.
Example C: Valley meeting a wall at a complex mitre
- Upstand: 110–130 mm along the wall margin for splash control.
- Edge: Rounded lip; radiused mitre; no tight inside corner.
- Code: 6–7; side laps 70–75 mm with a welt in exposure.
- Result: No scouring; clean discharge to sump/outlet.
12) Quality checks & handover photos
- Datum proved: Level marks and measured upstand heights recorded.
- Drip line: Straight, even, and consistent projection along the run.
- Throatings: Unbroken beneath noses; visible in close-ups.
- Laps: Within target dims; fixings absent in lap zones.
- Corners/radii: Soft, crack-free, and symmetrical.
- Overflow: Weirs/spouts photographed and explained for client records.
Because edges are visible, include a few eye-level photos for clients. That proof protects your warranty.
13) Edge defects—cause & cure
- Stained façades: Missing throating or buried nose.
Fix: Re-form the drip; add a continuous throating; keep noses proud of render. - Rippled noses: Tight clips or rough substrate.
Fix: Reset clip centres to allow slide; smooth the deck; add underlay. - Ponding at aprons: Flat back gutter or reverse fall.
Fix: Regrade to ≥ 1:80; verify with a datum; add saddle/overflow if needed. - Cracks at corners: Sharp folds or pinned laps.
Fix: Re-form with soft radii; free the lap; step up a code where spans demand. - Capillary ingress: Unwelted long edges in exposure.
Fix: Introduce welts; increase side laps to 70–75 mm.
14) What to buy & where
