Hertfordshire · England
Broad Colney External Mastic
External mastic for Broad Colney, by sealant specialists with 20+ years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Failed seals between different materials
- Moss and dirt in joints with no sealant left
- Movement joints filled with mortar instead of sealant
Walls and rooflines in Broad Colney
The South East is one of the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. Historic houses like High Elms Manor (about 4.1 miles west) are a reminder that the area around Broad Colney 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.
If you let a flat or house near Park Street station, failed wall and movement joints let damp in, so they’re worth checking between tenancies. For site and facilities teams at buildings such as Saint Bernadette Catholic Primary School, its movement joints, gutters and trims need looking after like any other building’s.
Broad Colney is about 3 miles south-east of St Albans, in Hertfordshire. Homes, rented property, offices and hotels in Broad Colney is covered for external mastic. The work is guaranteed for a year. Our Hertfordshire coverage runs to 381 places, and Broad Colney is one of them. There’s also a page for London, about 17 miles away.
Every address in AL2 is covered for external mastic, from the main roads to the quietest streets. Close by, we work in London Colney (1 mile north), Shenleybury (1 mile south-east), Tyttenhanger (2 miles north), Sleapshyde (3 miles north-east) and Colney Heath (3 miles north-east). Further out, we also cover Watford (6 miles south-west), Hemel Hempstead (7 miles west), Stevenage (14 miles north), St Albans (3 miles north-west), Welwyn Garden City (7 miles north-east) and Harpenden (7 miles north).
Around Broad Colney
In Broad Colney, that means homes and buildings near The White Lion pub and Samuel Ryder Academy, among other places. Broad Colney’s nearest station is Park Street station, about 1.9 miles north-west of the centre. Nearby you will also find Hilfield Castle (4.5 miles south) and Radlett and District Museum (2.5 miles south). Not far away are Verulamium Lake and Broad Colney Lakes.
About our external mastic in Broad Colney
A movement joint is only as good as its depth. Closed-cell backing rod sets the depth and stops the sealant sticking to the back, so it bonds to the two sides only and can stretch. If you have weathered mastic that no longer stretches and sealant that has lost its bond to the brick or render, we can put it right, on concrete & block, render & cladding joints and façade panels alike.
In a village or hamlet like Broad Colney, older cottages and farm buildings often stand in the open, where walls and rooflines take the weather head on. Gutter joints and wall joints there need a sealant that can flex and stay put.
Every job comes with a 12-month guarantee.
- Location
- Broad Colney (AL2)
- Region
- Hertfordshire
- Cover
- One year on every job
- Quotes
- A clear price before work begins
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
For landlords and businesses
If you manage several properties in or around Broad Colney, jobs at different addresses can go on one quote. Just tell us the addresses and what each one needs, and pictures by email help.
We work for letting agents and landlords as well as householders. Sealant work between tenants keeps a property looking cared for before the next move-in.
How to look after the new joints
Simple care keeps the joints in good condition. We recommend:
- Keep water from gutters off the wall
- Ask before painting over external sealant
- Do not let climbing plants root in the sealant
- Tell anyone working on the walls about the movement joints
If you have more work done on the wall, such as new render, cladding or an opening, show the contractor the movement joints. They must stay as flexible joints, never rendered or pointed over.
A joint that has stopped moving pushes the movement elsewhere, usually as cracking in the brickwork or render nearby. Resealing it early helps prevent that.
Common problems we fix in Broad Colney
Every building moves. Clay bricks expand slightly over their life, concrete and block shrink, and everything moves with temperature and wet. All of that ends up in the joint sealant.
People normally contact us after spotting something like this:
- Rigid filler in a joint that should flex
- Failed sealant between panels on a façade
- Plants rooting in failed movement joints
- Old sealant gone brittle and cracked
In the older streets around Church of St Peter, older walls, gutters and the joints where extensions meet them need a flexible sealant.
What your quote should include
- Who does the work, and how experienced they are
- What happens if the job turns out different
- What the quote includes, VAT included or not
- What the cure time is
Why act early in Broad Colney
An open joint keeps letting water into the wall with every downpour. In cold weather, frost can damage wet brick and render around the joint, so the damage spreads beyond the joint. Older cottages and farmhouses around Broad Colney can have timber floors and frames, and water through a failed joint can rot timber if it’s left.
Homes and businesses are quoted the same way: the amount of work, how we reach it and what it needs, plus any working-time requirements on site. Call for a quick quote and we will go through it with you.
Why book with us
- Full insurance on every job
- An ARBOMaster approved applicator
- Anti-fungal silicone where joints get wet
- Colour picked to suit the job
Take a look at how sealant jobs are priced and customer reviews.
DIY versus a professional finish
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and the joint depth matters as much as the finish.
The biggest DIY mistake is sealing over old sealant. Silicone does not stick to old silicone, so it peels away and traps moisture behind it. All the old material has to come out first.
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Broad Colney questions
Is Broad Colney within the area you cover?
Yes, Broad Colney is covered. Our work covers London and the South East, from towns to the smallest places. The journey is planned ahead, so it helps to know about access.
I let a flat near Park Street station. Can you help?
Yes, landlords and agents are among the people we work for, and several properties can go on one quote. Just call 0345 464 0079 or send us an email with the address and what needs doing, and we will give you a clear quote.
Will the old sealant be removed?
Yes. All of the old material is cut out and the joint cleaned before applying anything new.
Can you quote for more than one area?
Yes. Just list everything you need and you’ll get one quote.
What sealant do you use?
It depends on the joint: anti-fungal sanitary silicone in wet areas, and other sealants where joints move or face the weather. We use products from Arbo and Everbuild.
Will there be a smell?
That depends on the sealant. Some products have a noticeable smell, others very little.
What information do you need?
Only a few details: where it is, what you’ve noticed and how we reach it. After that, simply ring 0345 464 0079 or send us an email.
How long does external mastic take?
That depends on how much there is to do, but as a guide it takes anything from a few hours to several days, depending on the building. We will give you a better idea when we quote.
How the visit works
Every visit runs the same way: we look at the joints together, mask and protect the surrounding surfaces, carry out the job and tidy away. Most jobs take anything from a few hours to several days, depending on the building. In a small place like Broad Colney, access is normally the main thing to plan. If the job is outside, mention outbuildings, exposed walls and how to reach them.
- First, the joints are inspected and the access agreed.
- Every bit of old sealant and any mortar or debris is cut out.
- The faces are brushed clean and primed where the product requires it.
- Backing rod sized to the joint goes in to set the depth.
- We apply the sealant, tool it and check the whole run.
How to prepare
- For indoor joints, keep the area dry beforehand if you can
- Let us know if you’ve seen damp or leaks
- Keep pets and children clear of the area while we work
Getting a quote
A good description makes for an accurate quote. Tell us where the job is, what’s wrong and how much there is.
Related advice
How we quote for external mastic
Every job gets its own quote. This is what makes a difference:
- Mould in or behind the old joints
- Access and height
- When we can work, for business premises
- The number and length of the joints
A failed joint rarely gets cheaper to fix by waiting, because water and mould keep working on it. If you are unsure, ring 0345 464 0079 or drop us an email and we’ll give you an honest view and a quote.
Asking for a quote
You don’t need to know the technical terms. Just tell us:
- Any previous sealing or DIY work
- Where the job is, and your postcode
- A few pictures by email, if you can
- Access, such as stairs, a lift or height
Asking for a quote is easy: let us know the job and the location and its rough size. Photos by email help us understand the job, and we will take it from there.