Sealant packages for main contractors and developers

What a project needs from its mastic subcontractor

On most schemes the sealant package touches nearly every trade. Window installers leave perimeter joints to be closed. Bricklayers leave movement joints. Tilers and kitchen fitters hand over sanitary and worktop joints, and decorators want internal gaps caulked before the final coat. M&E trades leave service penetrations through fire-resisting walls and floors. Whoever holds the mastic package has to pick all of that up in sequence, to the specification, without holding back the programme.

We take on construction and new-build mastic packages for main contractors and developers on new-build and refurbishment schemes. Our applicators are CSCS-carded, we are CHAS accredited and a Constructionline member, and we carry £5m public liability insurance.

Typical joints on a new-build or refurbishment

• External window and door perimeters (facade and window perimeter sealing)
• Brick, block and panel movement joints (movement joint sealing)
• Sanitary joints in bathrooms, en-suites and washrooms
• Kitchen worktops, upstands and splashbacks
• Internal decorators’ caulk where the specification calls for it
• Fire-rated sealant at service penetrations and linear gaps where specified (fire-rated sealing)
• Coloured joints to the architect’s schedule (coloured sealant)

Planning around the programme

A mastic package runs best when areas are released in a predictable order. We agree a sequence with your site manager, plot by plot or floor by floor, and follow on as other trades finish. Sealant needs clean, dry, sound surfaces, so areas where wet trades are still drying out, or where dust is heavy, tend to cost time later. External joints depend on the weather: work may wait on cold, damp or frosty mornings, and we’ll raise it early if a date looks at risk.

CDM 2015 applies to construction work of every size, and your site induction, permits and rules come first. Tell us what site paperwork you need (RAMS, insurance certificate, CSCS details) and we’ll confirm with the quote. Our guide to CDM and RAMS for sealant work covers the basics.

Movement joints on a new building

New concrete shrinks as it dries, and brick and block walls move with temperature and moisture, so movement joints on a new building are working from the start. That is why joint design matters. The width must suit the expected movement and the sealant’s movement capability, and the depth is controlled with backing rod so the bead grips two faces and nothing behind. Where joints have been formed narrower than the drawings show, we raise it before sealing, because a gap that is too tight will tear the bead apart within a few cycles of movement. Our guide to joint width, depth and backing explains the numbers.

Specification queries, fire-rated sealing and snagging

We read the sealant schedule against the drawings before pricing. If a joint is too narrow for the specified product’s movement capability, or a substrate needs a primer the schedule doesn’t list, we raise a query instead of improvising. Our specification guide explains what a good schedule includes.

On fire-rated sealing, the designer, fire engineer and building control own the design and sign-off; we install to the product’s tested detail where it is specified. Near completion we can come back to close out sealant snags before the client walk-round, working from your list. See sealant snagging before handover for the items that most often hold things up.