Mastic & Sealant Replacement in London
Removal and replacement of perished mastic, silicone and polyurethane sealants on London curtain walls, cladding joints, window perimeters, panel joints and movement joints — all from rope, no scaffolding, no MEWP.
Why Sealant Failure Is the Hidden Cause of London Leaks
Most leaks on modern London office and residential towers are not roof leaks — they are sealant failures. Movement joints, curtain wall butt joints, panel-to-panel joints and window perimeter seals all rely on a single bead of polysulphide, polyurethane or silicone to keep water out. UV degrades the surface, building movement opens micro-tears, and after 10–15 years the seal is permeable even though it still looks intact from the ground.
The result is internal water ingress that the asset manager can't trace, because the failed joint is 12 floors up and the water tracks horizontally through the cavity before showing up on a different elevation.
Original-spec sealant on most London commercial stock from the 1990s and 2000s is now overdue for replacement. Manufacturers' service-life statements (typically 15–20 years on premium silicone, less on cheaper polyurethane) are now expired across most of the post-Big Bang office stock.
Replacement is straightforward — but only if you can get to every metre of joint, repeatably and without leaving access cost on the project for months. That is what rope access delivers.
Where We Renew Sealant
Curtain Wall Joints
Mullion, transom and stack joint sealant on stick-built and unitised curtain walling. Removal back to substrate, backer rod renewal, primed and re-sealed to manufacturer's joint design.
Cladding Panel Joints
Vertical and horizontal panel joints on stone, GRC, terracotta and metal rainscreen cladding. Re-sealing without disturbing the panel fixings or the rainscreen drainage path.
Window Perimeter Seals
Frame-to-structure seals on punched-window facades — the single most common source of perimeter leaks on London residential and office stock.
Movement & Expansion Joints
Structural movement joints in concrete frames, masonry and parapet copings — sized correctly for thermal and structural movement.
Coping & Parapet Joints
Coping stone joint renewal, parapet upstand seals and roof-to-wall transition joints — high-priority for landlord roof maintenance programmes.
Penetration & Plant Seals
M&E penetrations through external walls, AC condenser brackets, signage fixings — the small, easily overlooked items that account for a disproportionate share of leak callouts.
How We Replace Sealant the Right Way
1. Survey & specify. We measure linear metres by joint type and elevation, photograph current condition and recommend a sealant grade matched to the substrate (silicone for glazing/curtain wall, polyurethane for masonry, polysulphide for movement joints). On listed/conservation buildings we colour-match to the existing.
2. Remove & prepare. Old sealant cut out cleanly to substrate using oscillating tools — not just over-banded. Backer rod renewed (closed-cell PE for most joints; impregnated foam where fire-rated). Substrate cleaned and primed where the spec requires it.
3. Apply & tool. Sealant gunned to the manufacturer's joint design (typically 2:1 width:depth, never feather-edged). Tooled to a concave finish for movement capability. We don't shortcut the tooling — a poorly tooled joint will fail in the first cold/wet cycle.
4. QA & document. Every elevation photographed before, during and after. We log batch numbers and dates so the warranty chain is intact. For commercial clients we issue a sealed-joint schedule with linear-metre breakdown by elevation.
Mastic & Sealant Replacement — FAQ
Stop the Joints Leaking
Send the building address and elevation drawings or photos — we'll come back with a linear-metre cost by elevation and a programme that fits around tenants.