Oxfordshire · England
Cumnor External Mastic
Sealing brickwork movement joints, render, cladding and façade joints for Cumnor, backed by a one-year guarantee. Call for a quick quote.
- Leaking joints around cladding and façade panels
- Sealant pulling away from one side of the joint
- Movement joints with cracked, split or missing sealant
About our external mastic in Cumnor
Joints between dissimilar materials, like brick against render or concrete against a steel frame, see movement from both sides. A flexible sealant bridges the two where mortar or filler would crack. Typical jobs include joints with sealant missing in places and rigid filler in a joint that should flex, across render & cladding joints, concrete & block and brickwork movement joints.
In a village or hamlet like Cumnor, older cottages and farm buildings often stand in the open, so walls and rooflines take the full force of wind and rain. Gutter joints and wall joints there need a sealant that can flex and stay put.
A one-year guarantee comes as standard.
- Where
- Cumnor (OX2)
- Region
- Oxfordshire
- Guarantee
- A year, on every job
- Price
- A clear price before any work starts
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
Landlord and commercial work in Cumnor
We also work for property managers and facilities teams. We can quote a run of properties together, and we’re fully insured for the work.
In hotels, rooms out of use cost money, 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.
Aftercare tips
To keep the joints looking good and working properly:
- Deal with leaking gutters that soak the joints below
- Tell anyone working on the walls about the movement joints
- Keep high-pressure jets off the joints
- Look over the joints every year, ideally after winter
Follow the cure time we give you before the joint is knocked or disturbed. The surface skins over quickly, but full cure takes longer.
Gaps, plants or missing sealant in a joint are worth getting looked at. Earlier resealing means a smaller job and a better result.
Your questions about external mastic in Cumnor
I let a flat near Oxford station. Can you help?
Yes, landlords and agents are among the people we work for, and several properties can go on one quote. Just phone 0345 464 0079 or email us with the address and what needs doing, and we will give you a clear quote.
Is Cumnor within the area you cover?
Yes, smaller places are covered as well as towns. Our work covers London and the South East. Just mention lanes, gates or anything else about the route when you book.
Can you seal over the old sealant?
No. New silicone won’t bond to old silicone, and anything trapped underneath, including mould and water, stays there. It all has to come out first.
Are you insured?
Yes. We are fully insured, and we can confirm the details when we quote.
Can you seal joints between render and window frames?
Yes. The old joint is removed, both surfaces cleaned and primed where needed, and a flexible sealant applied. We pick a colour that works with both materials.
Can you work on commercial sites?
Yes, regularly. We can plan bigger jobs in stages.
Should I point up the gap in my brickwork?
No, not where the gap is a movement joint. Pointing it stops it working, and the wall may crack nearby. A flexible sealant is the right fill.
Where do you work from?
Mr Mastic is based in Crawley. Our applicators cover Cumnor.
What sealant work cannot fix
We will always be straight with you, so here’s what sealant can’t fix:
- Walls that need new movement joints cut into them
- Rising or penetrating damp from elsewhere in the wall
- Loose or hollow render, which needs re-rendering
If in doubt, ring 0345 464 0079 or send us an email and we’ll say what we think before you book.
Surfaces we seal
- Brickwork movement joints
- Concrete & block
- Joints between brick and frames
- Façade panels
- Copings & trims
- Render & cladding joints
What affects the cost of external mastic
The price is agreed before any work begins. It takes into account:
- Whether the work is at height
- How much old sealant there is and how hard it is to remove
- The size of the job
- Which sealant suits the joint
Rather than a set price list, we price the job in front of us: the amount of work, the old material and the access. The price is agreed before we begin.
What to tell us for a quote
The more you tell us, the more accurate the quote. When you ask for a quote, tell us:
- Any previous sealing or DIY work
- What the problem is, such as mould, gaps, leaks or cracking
- The type of property
- A few photos by email, if you can
If you’re in Cumnor and need external mastic, ring 0345 464 0079 or send us an email. Tell us what the problem is and where, and you’ll get a clear quote before we start.
Why it’s worth doing now in Cumnor
Low-modulus sealants stretch easily, so they put less strain on the joint edges. That protects surfaces like brick, render and concrete. Too stiff a sealant can pull at the edges and break them. Around Cumnor, older homes often have timber in their floors and frames, where water from a failed joint can cause rot if it’s left.
There are no prices on our website, because the cost depends so much on the job itself. Call for a quick quote.
Why choose Mr Mastic in Cumnor
- Every job guaranteed for a year
- Any old sealant cut out fully, not covered over
- You choose the colour before work begins
- 20+ years of sealant experience
Take a look at how sealant jobs are priced or what customers say.
Surface by surface
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 the movement is taken up.
Cladding and façade panels
If the façade has a specified sealant, that’s what we use, or one the system allows. Send us any details you have about the façade.
Cumnor buildings and the weather
London and the South East are among the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. With historic houses such as Appleton Manor (about 1.9 miles south-west) nearby, there’s older building stock in the area around Cumnor as well as newer homes. Where a home is older, older brick and stone need a sealant that suits them, at the right joint depth.
In the older streets around Church of St Michael, the joints between older walls, newer extensions and the roofline need a sealant that can move. If you let a flat or house near Oxford station, outside joints that have cracked can let damp into a rental, so check them between lets. Schools such as Cumnor Church of England School (Voluntary Controlled) are buildings too, and larger buildings have long runs of movement joint that eventually need resealing.
Cumnor is about 4 miles north-west of Abingdon-on-Thames, in Oxfordshire. Our applicators cover external mastic for homes and businesses in Cumnor and nearby, as part of our work across Oxfordshire. Our area takes in 443 places across Oxfordshire, large and small.
Work in OX2 works the same way as everywhere else we cover. If you need external mastic at a property on High Street, The Park and The Winnyards or anywhere close by, our applicators can take on the job. Nearby, we also carry out external mastic in Chawley (1 mile north-east), Filchampstead (1 mile north-west), Henwood (1 mile south-east), Dean Court (2 miles north-east) and Botley (2 miles north-east). Further out, we also cover Oxford (5 miles east), Didcot (9 miles south-east), Bicester (14 miles north-east), Abingdon-on-Thames (4 miles south-east), Witney (8 miles north-west) and Carterton (11 miles west).
Around Cumnor
Typical jobs here are in homes near The Vine Inn and Matthew Arnold School and the streets around them. For rail, the closest station is Oxford station, roughly 3.1 miles north-east of the centre. Other landmarks nearby include Westgate Shopping Centre (3.3 miles north-east) and Radcliffe Infirmary (3.6 miles north-east). For a walk, there’s Lashford Lane Fen and Cumnor Hill.
Nearby places to Cumnor
Also in Cumnor
What we do, step by step
You do not need to clear the whole room or building, only the area right around the joints. We protect the rest, and the work takes a few hours for a handful of joints, longer for a whole elevation in most cases. For a village or hamlet like Cumnor, the journey is planned in advance: let us know about lanes, gates and parking. We bring what the job needs, so it can be finished in one trip where possible.
- Each joint is checked and the colour of the new sealant agreed.
- We take out the old sealant until the faces are sound.
- Backing rod goes in so the sealant can stretch between the two faces.
- Primer is applied wherever the sealant needs it.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
Before we arrive
- Clear items away from the joints we’re working on
- Tell us about access, such as stairs, a lift or high-level joints
- Tell us about any previous sealing or DIY attempts
Ask for a quote
Every job is quoted individually, so the first step is telling us about yours. Simply phone 0345 464 0079 or send us an email and describe the job.