Mastic sealant contractors in St John's Wood
Work needed on a mastic joint in St John's Wood? We look at it, seal it with the right product and hand it over with a 12-month guarantee.
- Estate-wide sealant that is simply worn out
- Window mastic that has split and shrunk
- Occupiers reporting cold air round windows
Mastic sealing for businesses in St John's Wood
Photos, a specification or a quick description of the joints is enough to start a fixed quote.
St John's Wood: questions and answers
Will you take on work at estates like The Quadrant Business Centre, close to St John's Wood?
Yes. Our area takes in St John's Wood and its surroundings, with estates and business parks such as The Quadrant Business Centre included. Photos and a short description are enough for a first look.
Do you work in occupied care homes around St John's Wood?
Yes. We work around residents’ routines, a room or two at a time. Noise and disruption are kept to a minimum.
What’s the quickest route to a quote?
There are four steps: send details, receive a fixed quote, we carry out the work, and it’s guaranteed. The first step only needs photographs and a postcode.
Which sealant will you use?
Where there’s a specification, we use the product it names. If not, we choose for the movement, the surfaces and the conditions, in line with the manufacturer’s guidance.
How long do sealant joints last?
There’s no fixed lifespan: movement, exposure, cleaning, traffic and the product all play a part. Sealant joints are maintenance items, so inspect them regularly.
How long before the joints can be used?
That comes down to the sealant and the temperature. Some take light use quickly, others need longer to cure, so we will confirm the curing time on the day.
Will you quote for a small job?
Small jobs are welcome alongside larger packages. Photos and a description are enough to start.
Mastic sealing in St John's Wood
Different joints need different sealants. Low-modulus neutral-cure silicone suits many window perimeters and external movement joints, and MS polymer sealants stick well to many substrates and often take paint, and colours are confirmed for whichever product is used. Most enquiries involve communal area joints that look neglected and movement joints with sealant missing, on window and door perimeters on blocks, communal kitchens and washrooms and balcony and threshold joints. A specialist sealant contractor works differently from a general builder: in St John's Wood, that means joint design, primers and backing rod as standard.
Planning mastic work on a London block means notices to residents, access to flats and agreed working areas. Work is planned with the agent so residents get notice and access is arranged in advance.
Our 12-month guarantee is about workmanship, not wear and tear. Sealant wears with time, and movement, weather, cleaning and use decide how fast, so we’re clear about what is covered before work starts.
- Place
- St John's Wood (NW8, NW6, NW3)
- Wider area
- Greater London
- Cover
- A 12-month guarantee
- Quote
- Quoted before any work starts
- Phone
- 01277 525 020
- Page updated
- 3 November 2026
What we’re called out for in St John's Wood
In communal areas, joints take knocks from bins, bikes, buggies and deliveries, with joints near the floor and around doors suffering most. Cleaning products add to the wear.
These are often picked up first by site or facilities staff:
- Worn sealant at communal door frames
- Cracked, hardened mastic round windows on a block
- The same joint failures repeated across a portfolio
- Failed external movement joints
Schools and community buildings such as George Eliot Primary School need frame and external mastic kept sound like any building.
What to look for in a quote
- What site paperwork they can supply
- Can the work be phased to keep areas open?
- Who will actually carry out the work
- Proof of insurance
Looking after buildings in and around St John's Wood
For a London block, the agent or landlord normally handles notices to residents and access to flats. We plan around the notices and access you arrange. There are two care or nursing homes within about 2 miles of St John's Wood. For owners and operators of care buildings, window perimeters and external joints are best renewed in planned phases around residents.
If you look after a block within reach of South Hampstead station, less than half a mile to the north-west of St John's Wood, frame and balcony mastic can be renewed on one programme. Churches, halls and community buildings such as Church of All Souls are looked after by trustees and committees like any other owner, and their frames, doors and external joints need mastic renewed in time.
St John's Wood is about 1 mile south of Hampstead, in Greater London. We cover St John's Wood and the rest of Greater London, with the same fixed quotes and 12-month guarantee as everywhere else. St John's Wood is one of 764 places in Greater London on our list.
Business premises anywhere in NW8, NW6 and NW3 are within our area. For a building on The Lane, Hall Road and Hill Road or nearby, we can quote for mastic joints. With the A5205 nearby, St John's Wood is straightforward for us to reach. Sites close to St John's Wood are covered too, including South Hampstead (1 mile north), Swiss Cottage (1 mile north), Primrose Hill (1 mile north-east), Lisson Grove (1 mile south) and Haverstock (1 mile north-east). Further afield, our area takes in London (4 miles south-east), Kensington (3 miles south-west), St Pancras (3 miles east), Shoreditch (4 miles east), Walthamstow (7 miles north-east) and Hoxton (4 miles east).
Near you in St John's Wood
In St John's Wood, that means premises near Cecil Sharp House, Primrose Hill and Arnold House School. Also close by are Quintin Kynaston Community Academy (under half a mile north-west) and Cafe Med pub (less than half a mile north-west). There’s a railway station in St John's Wood itself: South Hampstead station. Nearby you will also find Hospital of St John and St Elizabeth (under half a mile south) and Montfichet's Tower (3.5 miles south-east). The countryside around St John's Wood includes The Long Water and Primrose Hill.
Towns and villages near St John's Wood
What else we do in St John's Wood
Diagnose, treat, sign off
A typical day starts with protection: masking tape along the joint edges and sheeting over anything nearby. On site, the work normally takes a few days for most blocks, with larger programmes scheduled building by building, and we clear our waste as we work. For a job in St John's Wood, access comes first. Give us the hours we can be on site and we’ll schedule to suit.
- First comes a look at the joints and, for older buildings, the asbestos records.
- A fixed quote covers the joints, products and order of work.
- We strip out the old sealant.
- Joint faces are cleaned, backed and resealed.
- We finish each building before moving to the next.
Before we start on site
- Share the asbestos register for older buildings
- Confirm the product named in the specification
- Tell staff and tenants when we’ll be in
Getting a fixed quote
Specifications, drawings and tender packages are welcome with any enquiry, and we’ll price against exactly what is specified. For smaller jobs, photographs and a description will do.
Read more
Building owners, agents and FMs in St John's Wood
For main contractors, we work as the sealant subcontractor. We work to your programme, your specification and your site rules.
Blocks and communal areas make up much of the work for housing associations and agents. We phase the work so people keep access, with each stage agreed with your site contact.
Leave it or put it right?
Adding sealant to cyclical maintenance is an easy win. Waiting until leaks appear means working under pressure with less control over timing. Repeat call-outs disrupt occupied London buildings, so cutting the old sealant out fully and doing it right once is the better route.
Whether it’s a single area or a whole estate, the same things set the price: scope, access, product and programme. Call for a quote and we will put a fixed figure on it.
Why us?
- One phone line for London, the South East and Scotland
- Fixed quotes based on photos, drawings or a visit
- Joints cleaned back to sound surfaces
- 12-month guarantee on workmanship
Read our cost guide or our accreditations.
What we can’t put right
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:
- Roof leaks, gutters or failed flashings that aren’t sealant joints
- Cracked or crumbling render, brick or stone at the joint edges (we will tell you if so)
- Old mastic suspected of containing asbestos, which must be tested and dealt with by a specialist first
If you are not sure, just call 01277 525 020 or email drawings and photos and we’ll give you a straight answer before you book.
Surfaces we seal
- Balcony and threshold joints
- Communal kitchens and washrooms
- Communal entrances and stairwells
- External wall and movement joints
- Window and door perimeters on blocks
- Shopfronts below residential blocks
Surface by surface
Tenement and older buildings
Older buildings, including Scotland’s sandstone tenements, have their own joint details. We look at the substrate before choosing a sealant.
Communal areas
Joints at low level in communal areas take knocks from bins, bikes and buggies, so they often need renewing sooner.