Greater London · England
Hampstead External Mastic
External mastic for Hampstead, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Hard, crazed mastic that has stopped moving
- Water getting into walls through failed joints
- Failed seals between different materials
External mastic in Hampstead
Low-level joints can usually be done from the ground. For joints higher up, give us some details of the building and we’ll confirm what’s needed to reach them safely. We’re often asked to deal with sealant pulling away from one side of the joint and old sealant gone brittle and cracked, across concrete & block, brickwork movement joints and copings & trims.
Newer London blocks are built with movement joints in brick and render, and with cladding joints sealed with mastic. Period houses have different weak points, such as gutter joints, trims and the line where an extension meets the old wall, and both kinds of building are found across London.
We guarantee the work for a year. If something is not right with it in that time, tell us and we’ll put it right.
- Where
- Hampstead (NW3, NW6, NW11, N2)
- Wider area
- Greater London
- Guarantee
- 12 months on all our work
- Quote
- A clear price before we start
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Walls and rooflines in Hampstead
Compared with the north and west, the South East gets less rain, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. With historic houses such as Fenton House (about 0.4 miles north) nearby, there’s older building stock in the area around Hampstead as well as newer homes. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material.
As a London address, Hampstead can be tricky for parking: let us know about parking bays, permits or a driveway. Letting a property close to Finchley Road & Frognal station? Then outside joints that have cracked can let damp into a rental, so check them between lets.
Hampstead is about 3 miles north-west of City of Westminster, in Greater London. Hampstead gets the same service as everywhere we cover: the old material taken out, joints prepared properly and a 12-month guarantee. Hampstead is one of 764 towns and villages in Greater London we cover for external mastic.
We cover every part of NW3, NW6, NW11 and N2 for external mastic and the streets around it. Streets in the area include Hampstead High Street, New End Square and The Mount Square, all of which we cover. Hampstead sits on or near the A1 and A502, so getting to you is simple. If you’re just outside Hampstead, we cover Greenhill (1 mile north-east), West Hampstead (1 mile west), Fortune Green (1 mile west), Vale of Health (1 mile north) and South Hampstead (1 mile south). Further out, we also cover London (5 miles south-east), City of Westminster (3 miles south-east), Marylebone (3 miles south-east), Kensington (4 miles south), St Pancras (3 miles south-east) and Shoreditch (5 miles south-east). Being one of Greater London’s larger places, Hampstead has homes, rented property and businesses of every kind.
Landmarks near Hampstead
Around Hampstead, our work takes us to homes and buildings near South Hampstead High School, Kilburn Grange Park and St Anthony's Preparatory School. Nearby too are King William IV Public House (under half a mile north-east) and Cecil Sharp House (1.7 miles south-east). Hampstead has its own railway station: Finchley Road & Frognal station. Other landmarks nearby include Isokon Gallery (0.8 miles east) and New End Hospital (less than half a mile north). Open spaces near Hampstead include Belsize Wood and The Long Water.
Your questions about external mastic in Hampstead
Is parking an issue for external mastic in Hampstead?
Parking in Hampstead, as in most of London, takes a little planning: a visitor permit or a bay close to the door helps a lot.
Can you do external mastic in Hampstead?
Yes, Hampstead is within the area we cover. Our work covers London and the South East. Just call 0345 464 0079 or send us an email with a few details of the job, and we’ll give you a clear quote.
Can you seal over the old sealant?
No, and we never do. It may look fine at first, but the new bead soon lifts. Removing the old sealant completely is the only lasting way.
What is a movement joint?
Most straight vertical gaps in brickwork are movement joints. It lets the bricks expand without cracking and needs a flexible seal, not mortar.
Do you work at height?
Each building is different. Send us pictures and a rough idea of the height.
Where are you based?
Mr Mastic is based in Crawley. We cover Hampstead and the rest of Greater London.
Do you have insurance?
Yes. We’re fully insured for domestic and commercial work.
How long does the job take?
A typical job takes anything from a few hours to several days, depending on the building, including the preparation. We’ll confirm how long when we quote.
Nearby places to Hampstead
More services for Hampstead
What we’re called out for in Hampstead
Joints sealed without backing rod, or far too deep, rarely last. Sealant bonded to three sides has nowhere to go and tears as soon as the joint widens.
These are the problems we are asked about most:
- Old sealant gone brittle and cracked
- Leaking joints around cladding and façade panels
- Weeds or debris growing in open joints
- Brick movement joints where the sealant has split
For site and facilities teams at buildings such as Fitzjohn's Primary School, movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Comparing quotes
- What product goes in the joint
- Whether they’re fully insured
- What happens if the job turns out different
- The length of the guarantee
When it isn’t the sealant
We won’t take on work that won’t last, so these are the limits:
- Walls that need new movement joints cut into them
- Render that’s blown, hollow or coming away
- Subsidence or other structural problems
If in doubt, ring 0345 464 0079 or email us and we’ll say what we think.
Joints and surfaces we work on
- Brickwork movement joints
- Concrete & block
- Render & cladding joints
- Joints between brick and frames
- Façade panels
- Copings & trims
Leave it or put it right?
A failed movement joint lets water into the wall and can run behind render or cladding. Resealing early keeps the job to the joint itself, instead of the wall and finishes around it. Converted houses in London often have a bathroom above someone else’s living room, and a slow leak from a failed seal can end up in the flat below. Dealing with it early is far simpler.
There are no prices on our website, because the cost depends so much on the job itself. Call for a quick quote.
Why book with us
- Neat joints and a tidy finish
- One-year guarantee on every job
- Domestic, commercial and hotel work
- Anti-fungal sanitary silicone in wet areas
Read our cost guide and what customers say.
What affects the cost of external mastic
You’ll get a clear quote before we start. It takes into account:
- How many areas need sealing
- Whether old sealant or filler has to be cut out
- The product the joint needs
- Access and height
What you pay reflects the work, not guesswork. That is why we ask a few questions first and send you a clear quote before any work starts.
What to tell us for a quote
The more you tell us, the more accurate the quote. When you get in contact, it helps to mention:
- The type of property
- The address or postcode of the job
- Any access issues, like height or stairs
- A few pictures by email, if you can
To get a quote, call 0345 464 0079 or drop us an email with the location and a short description of the problem. We will send you a clear quote before any work starts.
DIY sealant or a professional job?
The difference is mostly in the preparation and the product. Joints are cleaned back to sound surfaces and dried, and the sealant is matched to the joint and its conditions, then guaranteed for a year.
Not every job suits DIY: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
The process
Good joint work is mostly preparation, and we do not rush it. Joints are cleaned back and dried before anything new goes in. In total, it generally takes a few hours for a handful of joints, longer for a whole elevation. In a London area like Hampstead, the main things to plan are parking and access: let us know about parking, the floor we will be working on and any lift or shared entrance.
- We inspect the joints and agree which need resealing and how they’ll be reached.
- We cut out the failed sealant and rake out any dirt or growth.
- We clean both faces of the joint and prime them where the product calls for it.
- We push in closed-cell backing rod so the sealant is the right depth and bonds to the sides only.
- We gun in a flexible exterior sealant in a colour that suits the wall and tool it neatly.
Preparing for the visit
- Move anything stored near the joints
- Let us know about earlier repairs to the joints
- Tell us about access, such as stairs, a lift or high-level joints
Getting a quote
For external mastic in Hampstead, call 0345 464 0079 or send us an email. A short description of the job and where it is helps us quote, and you will get a clear quote before work begins.
Advice
Different surfaces, different methods
Render joints
Water behind render can lead to blown patches. Resealing the joints early keeps water out.
Copings and trims
A failed coping joint lets water into the top of the wall. Resealing them is a small job that protects a lot.