Sealant packages are often small in value compared with the rest of a project, so they get less scrutiny. Yet a poor sealant job is very visible, and failed joints let water, draughts and sometimes fire and smoke through. Choosing well up front saves call-backs later. This guide sets out the questions worth asking, whether you are a procurement lead, a facilities manager or a main contractor’s package manager.
Pre-qualification and site cards
Start with the basics your organisation already uses to vet suppliers:
- Health and safety assessment. CHAS assesses contractors’ health and safety standards for clients.
- Pre-qualification registers. Constructionline is a register buyers use to vet suppliers.
- Site cards. CSCS cards show a worker’s training and qualifications for their role and are commonly required on sites.
Ask for evidence rather than a logo on a website.
Insurance and paperwork
Ask for a current insurance certificate and check the public liability cover meets your requirement. Ask what site paperwork the contractor provides: risk assessments and method statements (RAMS), product data sheets and any permits they will need from you. Under CDM 2015, every construction job has duties attached, including small ones. Our CDM and RAMS guide explains what to expect.
Product knowledge
A good contractor should be able to explain, in plain words, why a particular sealant suits a joint. Ask:
- Which product will you use on each joint type, and why?
- How will you control depth, and will you use backing rod?
- Do the substrates need a primer with that product?
- Will the old sealant be fully cut out?
- What colours are available for that product?
Vague answers are a warning sign. See our specification guide for the background.
Need the work done? Mastic Doctor covers South East England, London and all of Scotland, with a 12-month guarantee on our workmanship. Send details for a fixed quote.
Fire-rated work
If the package includes fire-rated sealing, be precise. Ask which tested details the contractor will work to, and how they will record each seal. Ask whether they hold third-party installer certification, if your project requires it. Third-party certification is not a legal requirement, but many clients ask for it. Remember that fire stopping design and sign-off belong to the designer, fire engineer and building control, not the installer.
Guarantee, records and how the job runs
Ask what the guarantee covers and how long it lasts. Ask what records you’ll get at the end, and how the contractor will plan around your site hours and occupants. A clear process helps. Ours is simple: send details, get a fixed quote, we seal, and the work carries a 12-month guarantee. We are CHAS accredited, a Constructionline member, our applicators are CSCS-carded, and we hold £5m public liability insurance. More on our accreditations page.
Comparing quotes and checking coverage
Make sure each quote covers the same scope: full cut-out of old sealant, preparation, backing rod, primer where needed, the product and colour, access and phasing. A low price that leaves out preparation or access is not a saving. Our article on what affects commercial sealant cost explains the main factors.
Check the contractor works in your area and can cover all your sites. We work across the South East, Greater London and all of Scotland. Ask who your point of contact will be, how the contractor will report progress and how snags will be handled. On multi-site work, one contact and consistent paperwork save a lot of time for FMs and procurement teams.
Quick answers
What accreditations should a sealant contractor hold?
That depends on your organisation’s supplier rules. Common checks include a health and safety assessment such as CHAS, a pre-qualification register such as Constructionline, CSCS cards for site workers and suitable insurance.
Should the contractor visit before quoting?
Not always. Clear photos, drawings and joint lengths are often enough for a fixed quote. A site visit helps on larger or more complex jobs.
Is a longer guarantee always better?
Not necessarily. Check what the guarantee covers, the conditions attached and whether the scope and products are right. A sound specification and good workmanship matter more.
Related services
- Commercial sealant contractors
- Construction and new-build mastic
- Mastic sealing for building owners and managing agents
More advice
- CDM and RAMS Basics for Sealant Work
- What Affects the Cost of Commercial Sealant?
- Sealant Specification Guide for Contractors
- Planned Sealant Maintenance for FMs
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.