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Insured, guaranteed workmanship across Surrey and the South East

Onsite Sealants
Waterproofing and sealant specialists across the South East

Stop water getting into your building, for good

Onsite Sealants is a specialist waterproofing, sealant and damp proofing contractor working for homeowners, managing agents and main contractors across the South East. We diagnose the cause first, then fix it once.

01483 123 456Book a free survey
  • 10 year guarantee on tanking
  • Survey booked within 5 working days
  • Surrey, Hampshire, Berkshire and West Sussex
Placeholder image: waterproofing team applying a membrane to a basement wall
Placeholder imageReplace with a photograph of your own team on site.

Why building owners choose us

15+
years protecting buildings in the South East
2,400+
metres of joint sealed last year
10 yr
guarantee on tanking installations
4.9/5
average score across published reviews
Accreditations and cover
  • Property Care Association
  • CHAS Elite
  • Constructionline Gold
  • CSCS carded
  • £5m liability cover
What we do

Building protection, from a leaking balcony to a whole basement

Four core services, all delivered by our own directly employed teams rather than subcontracted out.

All services

  • Structural waterproofing

    Type A barrier, Type B integral and Type C drained systems designed around the building, the water table and how the space will be used.

    What this involves

  • Sealant application

    Precision mastic and silicone work on facades, curtain walling, wet rooms and industrial floors, with the right sealant chosen for the substrate and the movement it has to absorb.

    What this involves

  • Damp proofing

    A survey first, then targeted treatment: damp proof course injection, tanking, render repair or ventilation improvements, depending on what the moisture readings actually show.

    What this involves

  • Commercial contracts

    Scheduled inspection and repair programmes for managing agents, facilities teams and main contractors, with out-of-hours working where a site cannot be disrupted.

    What this involves
How it works

Four steps from first call to signed-off job

No sales visit, no pressure. A survey, a written specification, and a price that holds.

  1. Step 01

    Call or send us the details

    Tell us what you are seeing, where it is, and how long it has been happening. Photos help.

  2. Step 02

    Free site survey

    We take moisture readings, check the detailing and explain the options in plain language.

  3. Step 03

    Fixed written quotation

    A specification and price with no day rates or open-ended extras, usually within 48 hours.

  4. Step 04

    Work carried out and signed off

    Our own directly employed team, tidy sites, and a written guarantee on completion.

Before and after

The difference is easier to show than to describe

Two recent jobs. Same approach on both: find the cause, specify the fix in writing, then leave the place tidy.

  • Placeholder image: damp basement wall before waterproofing, Guildford project
    Before
    Placeholder image: finished dry basement room after waterproofing, Guildford project
    After
    Structural waterproofingResidential

    Basement conversion kept dry for a growing family

    Standing water and salting on the walls before work started. A Type C cavity drain system with a twin pump station now protects a finished habitable room.

    Location
    Guildford, Surrey
    Duration
    9 days on site
  • Placeholder image: failed flat roof covering before repair, Woking project
    Before
    Placeholder image: new liquid waterproofed roof terrace, Woking project
    After
    Liquid waterproofingResidential

    Leaking roof terrace above a kitchen extension

    Failed felt was letting water through to the ceiling below. Stripped back, re-boarded and finished with a cold-applied liquid membrane and new upstand detailing.

    Location
    Woking, Surrey
    Duration
    4 days on site
See the full gallery
What clients say

Work that holds up, and people who turn up

Placeholder copySwap these for real reviews once you have permission to publish names and locations.

  • They found the actual cause in twenty minutes after two other firms had guessed at it. The basement has been bone dry through two winters.
    Placeholder client nameBasement conversion, Guildford
  • Forty-two balconies resealed with residents still coming and going. Clear programme, no complaints, invoiced exactly as quoted.
    Placeholder managing agentApartment block, Reading
  • Worked three weekends around our picking operation so we never lost a shift. That flexibility is why we keep them on the framework.
    Placeholder facilities managerDistribution centre, Basingstoke
Free, no-obligation survey

Talk to someone who has done the job before

Tell us what you are seeing and we will tell you what it needs. Most surveys are booked within five working days.

01483 123 456Request a surveyhello@onsitesealants.com