Greater London · England
Harlington External Mastic
External mastic for Harlington, by sealant specialists with 20+ years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Joints with sealant missing in places
- Plants rooting in failed movement joints
- Hard, crazed mastic that has stopped moving
External mastic in Harlington
On houses, flats and commercial buildings across Harlington, we reseal joints in brickwork, render, cladding and façade panels. The preparation is the same whatever the wall: clean, sound faces and a controlled depth. We work on joints between brick and frames, concrete & block and copings & trims, and common reasons people get in touch are water getting into walls through failed joints and movement joints with cracked, split or missing sealant.
In London terraces and converted houses, gutters and walls are often shared with the house next door, so one failed joint can cause damp for more than one household. For a flat in Harlington, check the lease for who looks after the outside.
Our work is backed for twelve months, and the guarantee is the same wherever you are.
- Location
- Harlington (UB3, TW6, UB7)
- Wider area
- Greater London
- Guarantee
- One year on every job
- Quote
- Quoted before any work starts
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Walls and rooflines in Harlington
London terraces and converted houses often share gutters, downpipes and walls, so check who is responsible for the outside before booking. Rainfall in the South East is lower than in much of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
If you let a flat or house near Heathrow Terminals 2 & 3 Rail station, split movement joints are easy to miss on a rental until damp shows inside. Homes close to Church of St Peter and St Paul include some older properties, and an extension built onto an older house moves differently, and the joint between them takes the strain.
Harlington is about 2 miles south-east of West Drayton, in Greater London. We carry out external mastic for homes and businesses in Harlington and the surrounding area. We cover 764 towns and villages across Greater London, from the larger towns to small villages. Our London page covers work nearby (15 miles or so).
All of UB3, TW6 and UB7 is within our area for external mastic. If you need external mastic at a property on New Road, Bath Road and Manor Lane or anywhere close by, we can help. If you’re just outside Harlington, we cover Sipson (1 mile north-west), Hatton (1 mile south-east), Cranford (1 mile south-east), Heathrow (1 mile south-west) and Harmondsworth (2 miles west). Within a short drive, we also cover London (15 miles east), City of Westminster (12 miles east), Marylebone (13 miles east), Kensington (10 miles east), St Pancras (14 miles east) and Hoxton (15 miles east).
Near you in Harlington
Typical jobs here are in homes near The Red Lion pub, Harlington Community School and Lake Farm Country Park and the streets around them. The closest station to Harlington is Heathrow Terminals 2 & 3 Rail station, roughly 1.2 miles south-west of the centre. Other landmarks nearby include Harlington (0.6 miles north-west) and Treaty Centre (3.4 miles east). Green spaces nearby include Staines Reservoirs and Crane Meadows.
DIY versus a professional finish
Not every job suits DIY: work at height, external movement joints, fire-rated sealant and large areas call for the right materials, safe access and experience.
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and getting the depth right matters as much as the look.
Looking after it afterwards
Simple care keeps the joints in good condition. Our advice:
- Keep high-pressure jets off the joints
- Leave the joints unpainted unless we’ve said otherwise
- Keep water from gutters off the wall
- Do not let climbing plants root in the sealant
Only paint over the joint if we have confirmed the sealant can take paint. Many exterior sealants are not designed to be painted, and paint can crack as the joint moves.
Water getting behind cladding or render can go unnoticed for a long time. By the time there’s a damp patch, the damage can be well established.
When it isn’t the sealant
We’d rather tell you now than do work that won’t last, so here’s what sealant can’t put right:
- Adding movement joints to masonry that has none
- Render that is blown, hollow or coming away
- Cracked brickwork or render that needs a builder or plasterer
If you are not sure, just call 0345 464 0079 or email us and we will give you a straight answer before you book.
Where we work in Harlington
- Joints between brick and frames
- Façade panels
- Render & cladding joints
- Brickwork movement joints
- Concrete & block
- Copings & trims
How the job changes by surface
Concrete and blockwork
Blockwork and concrete shrink over time and move with the seasons. Their movement joints are sealed over backing rod with a flexible sealant.
Joints between dissimilar materials
Brick against render, concrete against metal, stone against timber: every change of material is a joint. A flexible sealant bridges the two so neither cracks the other.
Common problems we fix in Harlington
Sometimes a movement joint was filled with mortar or a rigid filler by mistake. With the joint locked solid, the movement turns into cracks elsewhere in the wall.
These are the problems we’re asked about most:
- Brick movement joints where the sealant has split
- Cracked joints where brick meets render or frames
- Weeds or debris growing in open joints
- Rigid filler in a joint that should flex
As a London address, Harlington can be tricky for parking: let us know about parking bays, permits or a driveway.
Before you book anyone
- How much experience the applicator has
- Whether the sealant suits the joint
- The length of the guarantee
- Is the old sealant removed completely?
Common questions in Harlington
Is parking an issue for external mastic in Harlington?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. That way the visit can be planned around it.
Do you cover Harlington for external mastic?
Yes. We work across London and the South East, and Harlington is part of that. You can ring 0345 464 0079 or send us an email and tell us what needs doing, and we will give you a clear price.
Can you reach joints on upper floors?
That depends on how high the joints are and the ground below. Low-level joints are straightforward; for higher ones, send details and we’ll confirm the access.
Can you do several jobs on one visit?
Yes, we can. Several rooms, windows or areas can go on one quote.
I rent my home. Can I book you?
Of course. Check with your landlord; we can send the quote to them too.
Where do you work from?
We are a Crawley-based firm, with over 20 years’ experience. We work across South East England, London and Scotland.
Is it messy?
No. We work neatly, protect the area around the joints and tidy up afterwards.
Is it OK to fill a movement joint with cement?
No. Mortar locks the joint solid, so the wall cracks somewhere else instead. It needs a flexible sealant over backing rod.
What affects the cost of external mastic
Some jobs are bigger than they look, and some smaller. The main factors:
- Mould in or behind the old joints
- The amount of work
- Working hours on commercial sites
- How easy the joints are to reach
Doing several joints on one visit normally makes better use of the time than several visits, so it’s worth mentioning everything you’d like done. We will send you a clear quote for the lot.
What to tell us for a quote
Before you ask for a quote, have a think about:
- Any previous sealing or DIY work
- The rough size of the job
- What’s wrong with the joints now
- Any access issues, like height or stairs
To get a quote, phone 0345 464 0079 or drop us an email and tell us where the job is and what the problem looks like. We’ll give you a clear quote before any work starts.
Places near Harlington
What else we do in Harlington
What happens on the day
There’s no need to move everything out, just the space around the work. We protect the rest, and the job takes a few hours for a handful of joints, longer for a whole elevation in most cases. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Harlington. It helps if you can point us to a visitor permit or a bay close to the door.
- We start by checking each joint, agreeing the ones to redo and how we’ll reach them.
- We cut out the failed sealant and rake out any dirt or growth.
- Both sides are cleaned back to sound material and primed if needed.
- Closed-cell backing rod is fitted to set the depth and stop three-sided bonding.
- A flexible exterior sealant is applied and tooled in a colour to suit the wall.
Preparing for the visit
- Plan for the work area to be out of bounds to pets and children
- Let us know if you’ve seen damp or leaks
- Tell us about access, such as stairs, a lift or high-level joints
Getting a quote
There’s no standard price list, as no two jobs are quite the same. Instead, we give you a clear price for your job. To arrange one, call 0345 464 0079 or drop us an email.