Buckinghamshire · England
Grendon Underwood External Mastic
Problem with your movement joints in Grendon Underwood? We cut out the old, prepare the joints and apply the right sealant.
- Old sealant gone brittle and cracked
- Sealant that has lost its bond to the brick or render
- Cracked joints where brick meets render or frames
External mastic in Grendon Underwood
External mastic is a job where short cuts show quickly. New sealant over old, joints packed with mortar and beads with no backing all tend to fail early. We take the old material out and do it properly. Common call-outs are for rain getting behind render or cladding at a joint and gaps where render, brick and frames meet, across joints between brick and frames, copings & trims and brickwork movement joints.
In a village or hamlet like Grendon Underwood, older cottages and farm buildings often stand in the open, so walls and rooflines take the full force of wind and rain. Joints on those walls need a sealant that moves with the building and stays in place.
The work is covered for a year after we finish. If anything is not right with it, phone 0345 464 0079 or email us.
- Where
- Grendon Underwood (HP18)
- Region
- Buckinghamshire
- Guarantee
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
What affects the quote in Grendon Underwood
Every job gets its own quote. These are the things that affect it:
- The product the joint needs
- Whether old sealant or filler has to be cut out
- Whether there’s mould to deal with
- How many rooms, windows or areas are involved
No two jobs are quite the same, so each one gets its own quote. Size, access and the product the joint needs all play a part, and we’ll explain the quote if you ask.
Asking for a quote
To help us quote quickly, please include:
- A few pictures by email, if you can
- Where the job is, and your postcode
- The problem you’ve noticed
- Any previous sealing or DIY work
Every job is quoted individually, so the first step is telling us about yours. Just call 0345 464 0079 or drop us an email with the details.
Your questions about external mastic in Grendon Underwood
Do you cover smaller places like Grendon Underwood?
Yes, we do. Our work covers London and the South East, and smaller places are part of that. Longer journeys are simply planned in advance.
Do you cover Grendon Underwood for external mastic?
Yes. Our work covers London and the South East, and Grendon Underwood is part of that. Just call 0345 464 0079 or send us an email with a few details of the job.
Can you seal joints between two different materials?
Yes. Joints between dissimilar materials are a big part of external work. The sealant is chosen to bond to both sides with primer where required.
How long will you be here?
As a guide, most jobs take a few hours for a handful of joints, longer for a whole elevation. Bigger jobs take longer, and we’ll say how long yours will take.
Can tenants book the work?
We’re happy to deal with the tenant, landlord or agent. Just make sure your landlord agrees.
When will the joints need doing again?
It varies from wall to wall: sunny, exposed elevations and busy joints wear faster. A yearly look will tell you when they need doing. Every job carries our one-year guarantee.
Do you guarantee your work?
Yes, for a year. If there’s a problem with our work in that time, tell us and we’ll put it right.
Are you insured?
Yes. Mr Mastic is fully insured.
How it works
All our tools and materials come with us in the van. After a quick look at the joints together, the area is protected and the work begins. It normally takes a few hours for a handful of joints, longer for a whole elevation. In a small place like Grendon Underwood, access is generally the main thing to plan. For outside work, also let us know about exposed walls and any outbuildings involved.
- First we look over the joints with you, agree which to renew and talk through access.
- Old sealant and any debris are cut and raked out.
- Both sides are cleaned back to sound material and primed if needed.
- Backing rod goes in next, setting the depth and keeping the sealant off the back of the joint.
- We gun in a flexible exterior sealant in a colour that suits the wall and tool it neatly.
How to prepare
- Move anything stored near the joints
- For business premises, tell us about site rules or sign-in
- Try not to wet indoor joints just before the visit
Ask for a quote
Getting a quote is simple: tell us what needs doing and where, and roughly how big it is. Photos by email help us understand the job, and we’ll take it from there.
Advice
Surface by surface
Brickwork movement joints
People sometimes point up a brick movement joint by mistake. If that is happened, we rake it out and reseal it properly if the joint can be cleared.
Cladding and façade panels
Panels heat up and cool down quickly, so the joint sealant has to cope with frequent movement. We choose the product to suit.
Landlords, agents and businesses in Grendon Underwood
Businesses can book us for washrooms, kitchens, offices and more. On commercial sites, working times can be discussed when we quote.
For anyone letting property in or around Grendon Underwood, several properties can go on one quote. Just tell us the addresses and what each one needs.
DIY sealant or a professional job?
Some sealant jobs are within reach of a careful DIYer, such as a straightforward joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
Some jobs are best left to a professional: work at height, external movement joints, fire-rated sealant and large areas call for the right materials, safe access and experience.
Signs you need external mastic in Grendon Underwood
UV, rain and frost all age exterior sealant. Over the years it hardens, cracks on the surface and loses its give, so the joint eventually tears or comes away from one side.
If you can see any of these, it’s time to have the joints looked at:
- Joints where the bead has come unstuck
- Brick movement joints where the sealant has split
- Panel joints letting water in
- Joints pointed up with cement by mistake
If you look after a building such as Grendon Underwood Combined School, larger buildings have long runs of movement joint that eventually need resealing.
Questions to ask before booking
- How much experience the applicator has
- How long to leave it before use
- What preparation is included
- Is the old sealant removed completely?
Grendon Underwood buildings and the weather
London and the South East are among the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. With historic houses such as Claydon House (about 3.6 miles north-east) nearby, there’s older building stock in the area around Grendon Underwood 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.
Homes close to Church of St Leonard include some older properties, and old and new materials meet at the roofline and walls, which is where sealant earns its keep.
Grendon Underwood is about 6 miles east of Bicester, in Buckinghamshire. Every kind of property in Grendon Underwood can book us for external mastic, old or new, large or small. The work is guaranteed for a year. Grendon Underwood is one of 263 places in Buckinghamshire we cover. For nearby work, see our Oxford page (13 miles or so).
Here we cover the HP18 postcode area for external mastic. We cover properties on Main Street, The Firs and Darley's Close and the roads around them. Nearby, we also carry out external mastic in Edgcott (1 mile north), Ludgershall (2 miles south-west), Piddington (3 miles south-west), Blackthorn (4 miles west) and Brill (5 miles south-west). We also work in nearby towns such as Aylesbury (9 miles south-east), Buckingham (8 miles north), Elmhurst (9 miles south-east), Southcourt (10 miles south-east), Princes Risborough (13 miles south-east) and Haydon Hill (8 miles south-east).
Near you in Grendon Underwood
Open spaces near Grendon Underwood include Upper Ray Meadows.
Why it’s worth doing now in Grendon Underwood
A low-modulus sealant is chosen because it moves without pulling hard at the edges. That matters on brick, render and concrete, which can be weaker at the face. Too stiff a sealant can pull at the edges and break them. Older cottages and farmhouses around Grendon Underwood can have timber floors and frames, where water from a failed joint can cause rot if it’s left.
Instead of a standard rate, we look at what your job involves: the amount of work, the old material and the access. You will know the price before we begin.
Why choose Mr Mastic in Grendon Underwood
- Anti-fungal silicone where joints get wet
- We never seal over old sealant
- Arbo and Everbuild products
- Homes, businesses and hotels
Take a look at our cost guide and customer reviews.