Introduction
Chasing walls looks simple until you hit a live cable, crack a wall, or the patch ghosts through the paint. This guide breaks down chases #plastering #tradesman #diy #homerenovation so you can cut clean channels, fix services properly, and plaster them out to an invisible finish. We’ll cover safe zones, structural limits, tools, step-by-step plastering, and the business side—quotes, client expectations, and handover. Whether you’re a tradesman coaching a mate or a DIYer upgrading your home, you’ll get practical tips you can use on the next room you tackle.
Quick Answer: Chases #plastering #tradesman #diy #homerenovation means cutting channels in walls for cables or pipes, securing services in safe zones, and backfilling with the right basecoat before a skim. Follow structural limits (typically one-third wall thickness for vertical, one-sixth for horizontal), prime, fill in layers, scrim edges, and finish flat.
Table of Contents
Key Takeaways
- Mark safe zones first: within 150 mm of corners/ceiling and directly in line with accessories.
- Keep vertical chases typically under one-third of wall thickness; horizontal under one-sixth.
- Fill deep chases in layers less than 15 mm, scrim the edges, then skim for a flat finish.
- Use 20 mm or 25 mm conduit for cables and protect pipes with foam sleeves to prevent cracking.
- Document lengths and locations; proposals and invoices are faster when you record on site using tools like Donizo.
Understanding Chases #plastering #tradesman #diy #homerenovation
Chases are recessed channels cut into masonry or plaster to run cables, conduits, or pipes. In chases #plastering #tradesman #diy #homerenovation work, the objective is a neat path that won’t weaken the wall, won’t crack later, and disappears after plaster. You’re balancing three things: compliance (safe zones and building guidance), durability (secure services and proper materials), and finish (flat, no ghosting).
Many contractors rush the cut and pay for it during finishing. The smarter play is to plan the route, size the chase correctly for the service—say 20 mm conduit or 15 mm copper—and decide the fill system before you start.
Planning, Safe Zones, and Structural Limits
Safe Zones for Services
- Vertical routes directly above and below switches and sockets.
- Horizontal routes directly to the left or right of accessories.
- Within 150 mm of wall corners, and within 150 mm of the ceiling line.
These are common routes used so future drilling is safer. If it’s not in a safe zone, expect callbacks.
Structural Limits (General Guidance)
- Vertical chases: commonly kept to less than one-third of the wall thickness.
- Horizontal chases: commonly kept to less than one-sixth of the wall thickness.
Load-bearing or slender walls need extra caution. If in doubt, speak to the designer/engineer before cutting. Avoid back-to-back chases on opposite sides of the same wall and keep well clear of openings and lintels.
Services and Sizing
- Cables: 20 mm or 25 mm conduit is typical. Add 6–10 mm cover for plaster over the highest point.
- Pipes: 15 mm and 22 mm copper are common. Insulate or sleeve to allow movement and reduce cracking/noise.
Plan the chase width and depth so you don’t overcut. For a 20 mm conduit, many contractors cut a 30–35 mm wide chase at roughly 25–30 mm depth in plaster plus a few millimetres into the block to allow a thin, strong backfill.
- Wall chaser with twin diamond blades (and adjustable depth) plus dust extraction.
- SDS drill and cold chisel for tight corners.
- Detector for live cables/pipes; isolate circuits before cutting.
- PPE: P3 mask, eye protection, ear defenders, gloves.
Tip: Good dust extraction captures most dust and keeps the site livable, especially on occupied renovations.
Step-By-Step: Cutting, Fixing, and Backfilling Chases
1. Mark and Check
- Mark the route in safe zones with a level or laser.
- Scan for existing services. Many contractors find a quick pass with a detector prevents the worst kind of day.
- Brief the client on visible disruption and noise. Note metreage here—using Donizo Voice to Proposal while you walk the job can save 10–15 minutes per room and prevents missed items.
2. Cut the Chase
- Set the chaser depth to the minimum needed; avoid gouging.
- Score both sides, then break out the centre with an SDS or bolster.
- Square ends near boxes to avoid thin, weak edges.
Common mistake: Overcutting horizontally. Keep horizontal runs as shallow and short as possible—less than one-sixth wall thickness is a sensible cap.
3. Fix Services
- Cables: Use 20 mm or 25 mm conduit or capping; clip at 300–500 mm centres for tidy alignment.
- Pipes: Use pipe clips every 500–600 mm. Sleeve or insulate (especially hot feeds) to allow slight movement.
- Boxes: Set flush or 2–3 mm proud if you’ll skim the whole wall; otherwise flush to the finished plane.
Pro tip: For multi-gang boxes, laser the height and use a straightedge to align. It saves you 20 minutes of fiddling later.
4. Prime and Backfill
- Dust off and prime the chase sides with PVA (about 3:1 water:PVA) or a grit primer where needed.
- Deep fills: Build in layers less than 15 mm each. Scratch each layer lightly for key.
- Feather 100–150 mm beyond the chase edges to avoid a hump.
5. Let It Firm, Then Tidy
- Allow the base to firm up (commonly 1–2 hours depending on product and temperature). Don’t rush—thumb pressure should not leave a deep mark before the next coat.
- Rub back any high spots to keep the profile flat.
Plastering Over Chases #plastering #tradesman #diy #homerenovation
Basecoats and Finishes
Choosing the right fill matters in chases #plastering #tradesman #diy #homerenovation. Here’s a quick comparison:
| Material | Where It Shines | Watch-Outs |
|---|
| Bonding plaster | Deep, internal chases; quick build in layers | Not for consistently wet areas |
| Hardwall | Robust base on medium-high suction backgrounds | Faster set; mix only what you’ll use |
| Sand/cement | Damp-prone areas or where impact resistance is key | Longer cure; needs good key |
| Multi-finish | Final skim over set basecoats | Working time typically 20–40 minutes |
Method for an Invisible Patch
- Prime: Lightly PVA surrounding area (3:1) and let it tack.
- Fill: Build base in layers under 15 mm. Scratch each pass.
- Scrim: Bed mesh tape over the chase edges to stop hairline cracks.
- Skim: Two tight coats of finish. Keep your second coat within 20–30 minutes of the first.
- Flatten and Polish: As it firms, trowel flats and edges. Aim for less than 1 mm deviation over 1.2 m.
Commonly, leaving basecoats 24 hours before skimming gives a steadier finish. On small chases, same-day skim is fine if the base is firm and not pulling excessively.
Finishing Tips
- Feather wide—300 mm beyond the chase is normal for flats walls.
- Over radiators or in sunny bays, control drying with light misting or shade to prevent crazing.
- If the whole wall is tired, reskim the full face; it’s often faster and cleaner than blending multiple patches.
Quality Control, Pricing, and Handover
Snagging and QC
- Straightness: Check with a 1.2 m straightedge—aim for less than 1 mm deviation.
- Fixings: Confirm conduit clips and pipe clips are firm before covering.
- Safe Zones: Photograph final routes before plaster. It’s a lifesaver when a client wants to hang a shelf later.
Pricing and Documentation
Many contractors price chases by metre plus per box/tee, then add for fill and skim. Keep it transparent: specify metreage, number of boxes, fill type (bonding, hardwall, sand/cement), and whether you’re skimming the whole wall or blending. Capture this on site with Donizo:
- Voice to Proposal: Record metreage and details hands-free.
- Send Proposal: Branded PDF with client portal access.
- E-signature Integration: Get it signed before you cut.
- Invoice Management: Convert accepted proposals to invoices in one click.
This flow commonly reduces back-and-forth and can save a few hours each week across multiple jobs. It also protects you if a client adds extras mid-job—just update and resend. [Learn more about invoicing].
Client Handover
- Photos of safe zones and final finish.
- Care notes: light sanding after full dry if needed; recommend mist coat before paint.
- Warranty note on hairlines: if building movement is ongoing, note limitations.
FAQ
What Depth Should A Wall Chase Be?
In general, size chases to the minimum needed to house the service plus a 6–10 mm plaster cover. A typical 20 mm conduit often needs about 25–30 mm total depth through plaster and a little into the block. For structure, keep vertical chases under one-third wall thickness and horizontal under one-sixth.
Can I Chase Load-Bearing Walls?
You can, but be cautious. Keep vertical chases shallow and narrow, avoid long horizontal chases, and never chase both sides of the same wall in the same area. If you’re unsure of the wall type or the load path, get a designer or structural engineer to advise before cutting.
How Do I Stop Cracks Over Chases?
Use the right fill (bonding or hardwall in layers under 15 mm), scratch each layer, and bed a mesh scrim over the chase edges. Allow adequate set (commonly 24 hours for basecoats) before skimming. Control rapid drying and avoid bridging over moving pipes—sleeve or insulate them to limit movement transfer.
Are There Rules About Where I Can Run Cables?
Yes—use safe zones: within 150 mm of corners and ceilings, and directly vertical or horizontal to switches and sockets. This applies widely in domestic work so future fixings avoid cables. Photograph your chases before covering so the route is documented for the client.
What’s The Best Filler For Deep Chases?
For most internal chases, bonding or hardwall in layered passes works well. In damp-prone areas, sand/cement is more durable. Always prime the background, build in layers under 15 mm, and finish with a multi-finish skim for a flat, paint-ready surface.
Conclusion
Done right, chases #plastering #tradesman #diy #homerenovation is straightforward: plan safe zones, respect structural limits (one-third vertical, one-sixth horizontal), build basecoats in layers under 15 mm, scrim edges, and skim flat within 20–40 minutes working time. Photograph routes, note metreage, and set expectations in writing. Capture details and generate a professional proposal with Donizo, get e-signed approval, and convert to an invoice in one click—so you spend more time on the wall and less in the inbox. Next step: walk your next job, record the chase plan, and send a same-day proposal.