Fire Stopping in Knebworth
Fire-rated and intumescent sealing of service penetrations and linear gaps across Knebworth, by CSCS-carded applicators. Fully insured and CHAS accredited.
- Builders’ foam or ordinary silicone in compartment walls
- Unsealed penetrations discovered above suspended ceilings
- Head-of-wall gaps with no fire seal
Fire stopping near Knebworth
Photos, a specification or a quick description of the joints is enough to start a fixed quote.
Leave it or put it right?
Sealing behind the M&E trades area by area beats a sweep at the end. While the area is still open, every opening is easy to see and reach. A failed joint lets water into a building whatever its size. Early resealing avoids the damage that follows a leak.
Larger quantities, tricky access or phasing all shape the price. So do site requirements such as inductions and permits, along with the time of year for external work.
Why us?
- A fixed quote before work starts
- Public liability insurance in place
- Constructionline member
- CHAS accredited contractor
Read our cost guide and how we’re accredited.
Fire stopping in Knebworth
Opened ceilings and riser doors often reveal service openings nobody sealed. If a specification already covers those walls and floors, we can reseal to it using the product and detail it sets out. With no specification in place, the first step sits with your designer or fire engineer, not with us. We work on joints between fire-resisting walls and floors, service gaps in risers and cable penetrations, and what we are called in for most is seals disturbed by maintenance and left open and non-fire-rated filler around services. Facilities teams, main contractors and managing agents in Knebworth tend to want the same three things: a clear scope, tidy work and joints that don’t fail again.
Buildings in a smaller place such as Knebworth that need fire-rated sealing are typically schools, care homes, surgeries, small offices and flats over shops. Around those penetrations, fire-rated sealant is installed if specified, with depth, backing and gap all as tested.
What our 12-month guarantee covers is the way we did the job: preparation, application and finish. Damage, later alterations by others and movement beyond what the joint was designed for sit outside it.
- Where
- Knebworth (SG3)
- Wider area
- Hertfordshire
- Cover
- 12 months on every job
- Quotes
- Quoted before any work starts
- Telephone
- 01277 525 020
- Updated
- 3 November 2026
Work for main contractors and building owners
Main contractors use us as their sealant subcontractor. Programme, specification and site rules come first, and our applicators hold CSCS cards.
We take on planned maintenance as well as one-off repairs: resealing failed joints building by building, on a schedule that suits your budget. Sites in Knebworth can sit alongside others in a wider programme across Hertfordshire.
Questions we’re asked in Knebworth
Can work at a site such as North Hertfordshire College - Stevenage Campus fit around teaching?
Yes. Tell us the term dates, vacation periods and access windows, and we will plan the work around them. Tell us which site documents you need, such as RAMS, our insurance certificate or CSCS details, and they’re confirmed with the quote.
What happens to BS 476 references for fire stopping in Knebworth?
References to BS 476 classes are being removed from Approved Document B from 2 September 2029, after which BS EN 13501-2 classification is the route, subject to transitional arrangements. The designer or fire engineer sets the specification, and we install the product to the manufacturer’s tested detail.
Will you quote for a small job?
Whatever the size, the process is the same: send details, get a fixed quote, we seal, guaranteed.
Do you take on multi-site work?
Yes. Multi-site work and planned programmes are a core part of the service, planned site by site to suit how each building is used.
Do you cover Knebworth?
Yes. We cover Knebworth, and you can phone 01277 525 020 or email us to get started.
Do you have public liability insurance?
Yes. Mastic Doctor is fully insured, public liability included.
Are you CHAS accredited?
Yes. We are CHAS accredited and a Constructionline member, which helps with supplier vetting.
Site staff or a sealant specialist?
Some joints are best left to specialists: for example fire-rated seals that must match a tested detail, trafficked floor joints and external movement joints. Getting these wrong typically costs more in the end than doing them right.
General builders and handymen seal joints, but it isn’t their main trade. A specialist prepares properly, controls joint depth and picks a product with the right movement class.
Nearby places to Knebworth
More services for Knebworth
Diagnose, treat, sign off
We bring the products specified for the job, along with primers and backing rod. Any old material is cut back to clean, sound faces, primer goes on where the manufacturer specifies it, and the sealant is tooled off neatly. What matters most for a job in Knebworth is a clear list of what needs doing, so send photos of each area. You’ll then get a fixed price for the work.
- First we go through the drawings, schedule or specification for the seals and ask about anything unclear.
- On site, each opening is checked against the tested detail it is meant to follow.
- Unsuitable fillers and loose debris are taken out of each opening.
- Mineral wool or other backing goes in wherever the detail asks.
- We apply the specified sealant to the depth and around the services as the detail shows.
- Openings that need a collar, wrap, batt or other product are flagged to you rather than filled with sealant.
What we need from you
- Tell us which areas need to stay in use
- Send your site hours and access windows
- Tell staff and tenants when we’ll be in
Request a quote
If there’s a specification, drawings or a tender package, send it with your enquiry, and we will price against exactly what is specified. Smaller jobs need nothing more than photographs and a few notes.
Read more
When something else is needed
Part of a good diagnosis is knowing where sealant stops. You will hear from us if the cause turns out to be one of these:
- Gaps in walls that were never built as compartment walls
- Fire risk assessments, a job for a competent assessor
- Openings that need collars, wraps, batts or boards rather than sealant
If you’re not sure, just give us a call on 01277 525 020 or email drawings and photos and we’ll give you a straight answer before you book.
What we seal
- Pipe penetrations
- Linear gaps at wall heads
- Joints between fire-resisting walls and floors
- Cable penetrations
- Service gaps in risers
- Small duct penetrations where the tested detail allows
What sets the cost
The price varies from site to site. Expect it to depend on:
- Working within restricted access windows
- The site’s rules and procedures
- Access and working height
- The total length or number of joints
The product called for affects the cost, as does the preparation each joint needs, from cutting out to priming and backing rod. Access, phasing and site rules also count.
What to include in your enquiry
Good information means a firmer quote. Helpful details to send:
- The site address and postcode
- Drawings or a marked-up plan, if available
- Asbestos survey details if the building is older
- What the building is and how it’s used
Every job follows the same four steps: send details, get a quote, we seal, guaranteed. The first step is to call 01277 525 020 or email the details over with what you know.
Fire stopping around Knebworth: what changes locally
Knebworth is about 26 miles from central London. Office refits around the commuter belt bring new cabling through fire-resisting walls. Approved Document B is the English guidance that covers fire stopping around openings and penetrations. References to the older BS 476 classes are being removed from it from 2 September 2029, after which the European classification, BS EN 13501-2, is the route, subject to transitional arrangements. Our part stays the same: the specified product, installed to its tested detail.
On a site such as Arlington Business Park, 1.9 miles north-west of Knebworth, every fit-out that runs new services through a compartment wall leaves penetrations to seal with the specified product. At a college such as North Hertfordshire College - Stevenage Campus, which lies north of Knebworth, checking penetration seals after summer M&E works is good practice. For a hotel such as The Roebuck Hotel, which lies north of Knebworth, penetration seals are worth checking after any refit or services upgrade.
Knebworth is about 3 miles south of Stevenage, in Hertfordshire. We cover commercial sites throughout Knebworth, for single jobs and planned programmes alike. Knebworth is one of 371 places in Hertfordshire on our list. For work in that direction, see our London page (26 miles or so).
We take on service penetrations across the SG3 postcode area, for business premises of every kind. Streets here include London Road, Deanscroft and Lytton Fields, and sites on any of them can send details for a fixed quote. Just outside Knebworth, we also work in Woolmer Green (1 mile south), Bragbury End (1 mile north-east), Oaklands (2 miles south), Datchworth (2 miles south-east) and Shephall (2 miles north). A short drive away, we cover Hemel Hempstead (14 miles south-west), Stevenage (3 miles north), St Albans (10 miles south-west), Bishop's Stortford (15 miles east), Welwyn Garden City (5 miles south) and Harpenden (8 miles south-west).
Near you in Knebworth
Locally, jobs take us to sites close to Barnwell School and Knebworth Park and the streets around them. Knebworth has its own railway station: Knebworth station. Well-known places in the area include Benington Castle (3.6 miles north-east) and Datchworth Museum (1.7 miles south-east). Green spaces nearby include Mardley Heath.