Greater London · England
External Mastic in Sidcup
We cover Sidcup for sealing brickwork movement joints, render, cladding and façade joints. Old material cut out, joints cleaned and sealed neatly and every job guaranteed for a year.
- Rigid filler in a joint that should flex
- Water getting into walls through failed joints
- Joints where the bead has come unstuck
External mastic in Sidcup, done properly
Many failed façade joints only get noticed once there’s a stain or a damp patch inside. We inspect them, agree which need doing and reseal with a weatherproof, flexible sealant in a colour to suit. If you have brick movement joints where the sealant has split and leaking joints around cladding and façade panels, we can put it right.
Modern London flats rely on sealed movement joints and cladding joints. Older terraces have their own weak points: gutter joints, roofline trims and the joint where an extension meets the original wall.
The work is covered for a year after we finish. If anything isn’t right with it, call 0345 464 0079 or email us.
- Location
- Sidcup (DA14, DA15, SE9, DA5)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
How we quote for external mastic
Every job gets its own quote. This is what makes a difference:
- Working hours on commercial sites
- Whether the work is at height
- How many rooms, windows or areas are involved
- The type of sealant required
Combining jobs into one visit normally makes better use of the time than several visits, so it’s worth mentioning everything you’d like done. We will give you a clear quote for the lot.
Asking for a quote
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- If it’s domestic, commercial or a hotel
- The rough size of the job
- A few photos by email, if you can
- Where the property is
Quotes start with a quick conversation. Describe the problem, the location and the size of the job, and we will explain how we’d tackle it. Whenever you are ready, ring 0345 464 0079 or email us.
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More services for Sidcup
Can I do it myself?
A careful DIYer can reseal a simple joint, such as a straightforward joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
The biggest DIY mistake is sealing over old sealant. Silicone doesn’t stick to old silicone, so it peels away and traps moisture behind it. Everything old must be removed first.
Different surfaces, different methods
Brickwork movement joints
Brick moves with heat and moisture, and grows a little over time. That movement goes into the joint, so its sealant has to stay flexible.
Concrete and blockwork
Concrete and block walls shrink as they dry and move with temperature. We reseal their joints with backing rod and a flexible product.
How it works
All our tools and materials come with us in the van. Once we have agreed what’s being done, we protect the area and start. It normally takes a few hours to a few days, depending on the length of joint and the access. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Sidcup. It helps if you can point us to a visitor permit or a bay close to the door.
- Each joint is checked and the colour of the new sealant agreed.
- Failed sealant is removed back to clean, sound faces.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Getting ready for the visit
- Let us know about stairs, lifts or work at height
- Mention any parking rules near the property
- Keep children and pets away from the work area
Getting a quote
If you are in Sidcup and need external mastic, ring 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 we start.
Advice
When something else is needed
We won’t take on work that will not last, so here’s what sealant can’t put right:
- Damp that is not coming from the joint
- Cracks in the bricks or render themselves, away from the joints
- Subsidence or other structural problems
Not sure which it is? You can call 0345 464 0079 or send us an email and we’ll tell you honestly before booking.
Where we work in Sidcup
- Joints between brick and frames
- Copings & trims
- Brickwork movement joints
- Render & cladding joints
- Façade panels
- Concrete & block
External mastic in Sidcup: local notes
Historic houses like Danson House (about 1.7 miles north) are a reminder that the area around Sidcup has older buildings as well as new. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material. The South East is one of the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day.
For landlords with property near Sidcup station, failed wall and movement joints let damp in, so they’re worth checking between tenancies. If you live in an older home near Holy Trinity Church, an extension built onto an older house moves differently, and the joint between them takes the strain. Schools such as Birkbeck Primary School are buildings too, and larger buildings have long runs of movement joint that eventually need resealing.
Sidcup is about 3 miles north of Orpington, in Greater London. Wherever you are in the DA14 postcode area, we cover external mastic for homes and businesses. Sidcup is one of 764 towns and villages in Greater London we cover. For nearby work, see our London page, about 10 miles away.
Work in DA14, DA15, SE9 and DA5 is quoted and booked the same way as anywhere else. Streets in the area include Station Road, High Street and Jubilee Way, and we cover them all. With the A211 and A2001 close by, Sidcup is easy for our applicators to reach for external mastic. We also cover the places around Sidcup: Albany Park (1 mile south), Blendon (1 mile north-east), Foots Cray (1 mile south-east), Bexley (2 miles north-east) and North Cray (2 miles east). We also work in nearby towns such as London (10 miles north-west), City of Westminster (12 miles north-west), Marylebone (12 miles north-west), Kensington (14 miles west), St Pancras (11 miles north-west) and Shoreditch (10 miles north-west).
What’s near Sidcup
Typical jobs here are in homes near The Alma pub, Waring Park and Chislehurst and Sidcup Grammar School and the streets around them. Sidcup has its own railway station: Sidcup station. A little further out are Queen Mary's Hospital (1 mile south) and Broadway Shopping Centre (2.4 miles north-east). Not far away are Summer Hill and The Tarn.
How to look after the new joints
A little care helps the new joints last. Our advice:
- Deal with leaking gutters that soak the joints below
- Point out the joints to other trades
- Never let anyone fill a movement joint with mortar
- Do not let climbing plants root in the sealant
Look over the joints once a year, ideally after winter. Splits, gaps at the edges or plants in the joint are early warning signs.
Once a joint cannot move, the wall finds another way, normally as cracking in the brickwork or render nearby. Resealing it early helps prevent that.
For landlords and businesses
Hotels need rooms back in use, so we plan the work room by room around your bookings where we can. Hotel work is part of what we do, alongside homes and businesses.
A neglected joint can let water reach the structure, which matters even more when someone else lives there. Keeping joints in good order is simple maintenance that we can handle for you.
FAQs for Sidcup
Can parking be tricky for a visit in Sidcup?
Parking in Sidcup, as in most of London, takes a little planning: a visitor permit or a bay close to the door helps a lot.
Do you work for landlords with property near Sidcup station?
Yes, rental work is part of what we do. Just ring 0345 464 0079 or email us and tell us about the property, and we’ll give you a clear quote.
Can a movement joint be filled with mortar?
No. Cement or mortar can’t stretch. If it has already been filled, we can generally cut it out and reseal it.
How long does external mastic last?
It varies with how exposed the wall is and how much the joint moves. Signs to watch for are cracking, hardening and gaps at the edges and have them redone then.
Are you ARBOMaster approved?
Yes. Mr Mastic is an ARBOMaster approved applicator, and we’re fully insured.
Is it messy?
No. We protect the surfaces around the joints, and we clear up the old sealant and our materials before we leave.
Are you insured?
Yes. We’re fully insured, with over 20 years’ experience in sealant work.
Is it OK to seal over old sealant?
No. We remove every bit of old sealant first, so the new sealant bonds properly.