Mastic Sealing in Old Knebworth
Planning work on a mastic joint in Old Knebworth? We look at it, seal it with the right product and hand it over with a 12-month guarantee.
- Damaged joints in communal entrances and corridors
- Open joints in brickwork or panels
- Estate-wide sealant that is simply worn out
Mastic sealing across Old Knebworth
Photos, a specification or a quick description of the joints is enough to start a fixed quote.
What the job involves on each surface
Window and door perimeters on blocks
Window and door perimeters are where most mastic failure shows. Old perimeter mastic is removed, the joint prepared and new sealant tooled in.
External movement joints
Brickwork, blockwork and panel joints let a building move. Failed sealant in a movement joint lets water in.
Mastic sealing in Old Knebworth
On a residential block, the work happens around people’s lives. Dates, areas and the order of work are agreed with you in advance, giving you what you need to notify residents. Communal entrances and stairs stay usable while we work. Site teams most often ask us about estate-wide sealant that is simply worn out and complaints coming in block by block, on window and door perimeters on blocks, balcony and threshold joints and external wall and movement joints. Whether you call it commercial sealant work, mastic application or joint sealing, the work in Old Knebworth is the same: the right product in a properly prepared joint.
For buildings around smaller places like Old Knebworth, we group work so one trip covers it. Photos of each elevation help us quote accurately.
The 12-month guarantee is for workmanship rather than wear and tear. How long a sealant joint lasts depends on movement, exposure, cleaning and use, so we spell out the cover before we begin.
- Location
- Old Knebworth (SG3)
- Wider area
- Hertfordshire
- Guarantee
- 12 months on every job
- Quote
- A fixed quote before we start
- Phone
- 01277 525 020
- Page updated
- 3 November 2026
Places near Old Knebworth
More services for Old Knebworth
For owners and agents in Old Knebworth
Old Knebworth sits in one of the drier corners of the country, the South East. Outside work still depends on dry joints, and the sunniest, most exposed sides of a building normally need attention first. Central London is about 26 miles from Old Knebworth. Around the capital’s commuter belt, managing agents look after many blocks close to stations and town centres; their frame mastic often ages block-wide.
If your remit includes a building such as Barnwell School, frame and door mastic can be programmed for the holidays. If you are responsible for a building such as Church of St Mary and St Thomas, frame and door mastic needs the same attention as any other property.
Old Knebworth is about 3 miles south-west of Stevenage, in Hertfordshire. Any commercial site in Old Knebworth is covered, for single jobs and planned programmes alike. 371 places across Hertfordshire fall within our area, including Old Knebworth. There’s a separate page for London, roughly 26 miles from Old Knebworth.
We take on mastic joints across the SG3 postcode area. We cover commercial and managed buildings on Old Knebworth Lane and Park Lane. Just outside Old Knebworth, we also work in Nup End Green (1 mile south-west), Driver's End (1 mile south-west), Rableyheath (1 mile south), Pottersheath (1 mile south) and Langley (2 miles north-west). Nearby towns on our patch include Hemel Hempstead (13 miles south-west), Stevenage (3 miles north-east), St Albans (10 miles south-west), Welwyn Garden City (5 miles south), Harpenden (7 miles south-west) and Hitchin (6 miles north-west).
Landmarks near Old Knebworth
We work on buildings around Knebworth Park and Robin Hood And Little John Public House. For rail, the closest station is Knebworth station, roughly 1 mile east of the centre. A little further out are Lister Hospital (3.7 miles north) and Stevenage Museum (2.2 miles north). The countryside around Old Knebworth includes Mardley Heath.
Honest limits
Before quoting, we check that sealant is the right answer. It isn’t the answer for:
- Leaks from above rather than through a joint
- Substrate edges that need repairing first
- Misted or failed double-glazed units
If in doubt, speak to us on 01277 525 020 or email the details over and we’ll say what we think before you book.
Joints and surfaces we work on
- Communal kitchens and washrooms
- Window and door perimeters on blocks
- Communal entrances and stairwells
- Balcony and threshold joints
- Shopfronts below residential blocks
- External wall and movement joints
Common problems we fix in Old Knebworth
UV and rain age external sealant. It stiffens, stops stretching and cracks most of all on the sunniest and most exposed elevations.
Common reasons buildings call us in:
- Estate-wide sealant that is simply worn out
- Worn sealant at communal door frames
- Open joints in brickwork or panels
- Cracked, hardened mastic round windows on a block
If you own or manage units on a site such as Arlington Business Park, which lies north of Old Knebworth, failed mastic on frames, door surrounds and external joints can be dealt with unit by unit.
Questions to ask before you book
- Their pre-qualification and accreditations
- Their plan for phasing and protecting the area
- Will failed sealant be removed rather than covered?
- Whether their applicators hold CSCS cards
On site: what to expect
In a busy building, we agree a sequence with your contact so the disruption stays in one area at once. Each area is protected, prepared and sealed, then handed back before we move to the next. Rural sites near Old Knebworth may need directions, gate codes or a contact on site. Add it to your enquiry and we’ll build it into the plan.
- A building-by-building inspection lists the failed joints.
- The quote is fixed and split as suits you.
- Dates and areas are agreed so occupiers can be told.
- Old mastic is removed and the joint faces prepared.
- New sealant goes in with backing rod and primer where needed.
- Each building is checked and signed off with the 12-month guarantee.
Getting the site ready
- Share your working hours and any access restrictions
- Explain the parking and delivery arrangements
- Let us know about inductions and permits
Request a quote
Every quote starts with the facts: the joints involved, quantities, access and the product called for. Send what you have, and we’ll arrange a site visit if anything is unclear.
Advice
Work for main contractors and building owners
FMs need a contractor who is easy to get on site. Let us know the documents you need (RAMS, insurance certificate, CSCS details) and we will confirm them with the quote.
We work for building owners and managing agents on everything from one building to a spread of sites. Several sites can go on one quote, so there’s one set of paperwork to deal with.
Should maintenance staff do it?
There’s also the paperwork. Main contractors and clients often ask for CSCS cards, RAMS and insurance details, and we will confirm the paperwork you need with the quote.
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.
FAQs: Old Knebworth
Is Old Knebworth off your patch?
No. Places such as Old Knebworth are covered as much as the big towns. London and every South East county are within our area. We plan jobs in smaller places so return trips are kept to a minimum.
Do you cover business parks and estates near Old Knebworth, such as Arlington Business Park?
Yes, sites like Arlington Business Park are within our area, along with the rest of Old Knebworth. A few photographs and the unit address let us price the work.
Will you come and look before quoting?
Photos, drawings or a schedule are often enough to quote. Where they aren’t, we arrange a site visit.
When can the area be used after sealing?
The product and site conditions decide that. Some products skin over quickly but need longer to cure fully, so we’ll confirm the curing time on the day.
Is it fine to apply new sealant on top of old?
No. We cut the old material out and clean the joint back before sealing, since fresh sealant will not bond reliably to aged material.
How do you handle work on occupied blocks?
The work is planned around occupiers. We agree the programme so you can notify occupiers and communal access is kept open.
Do you check for asbestos in old sealant?
In older buildings, old mastic can contain asbestos. We ask for the asbestos register or survey before work starts and suspect material is tested first.