Hertfordshire · England
St Albans External Mastic
Specialist external mastic for St Albans: the right sealant, proper preparation and a neat finish. Call for a quick quote.
- Water getting into walls through failed joints
- Brick movement joints where the sealant has split
- Rigid filler in a joint that should flex
DIY versus a professional finish
If you’ve already had a go yourself, that is fine. We remove it and do the joint properly, so tell us about it when you ask for a quote.
Sealing over old silicone is the commonest DIY error. New silicone won’t bond to old, so it lifts and traps water and mould underneath. All the old material has to come out first.
External mastic for homes and businesses in St Albans
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 matching colour. Typical jobs include water getting into walls through failed joints and movement joints with cracked, split or missing sealant, on render & cladding joints, copings & trims and brickwork movement joints.
A place the size of St Albans has buildings of every age, from older brick terraces to modern blocks with rendered or clad walls. Newer buildings rely on sealed movement joints, while older ones need their gutters, fascias and trims kept tight.
All our work is covered by our one-year guarantee, wherever you are in Hertfordshire.
- Place
- St Albans (AL1, AL3, AL4)
- Wider area
- Hertfordshire
- Guarantee
- One year on every job
- Price
- Quoted before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Common problems we fix in St Albans
The wrong product in a moving joint is a classic cause. A high-modulus or general-purpose sealant can be too rigid for a busy joint, so it pulls away from the edges.
Look out for any of the following:
- Sealant pulling away from one side of the joint
- Brick movement joints where the sealant has split
- Leaking joints around cladding and façade panels
- Weathered mastic that no longer stretches
If you look after a building such as Loreto College, movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Comparing quotes
- Whether you can choose the colour
- What guarantee comes with the work
- Whether all the old sealant comes out first
- What happens if the job turns out different
What affects the quote in St Albans
Call for a quick quote. What matters most is:
- The old material and how stubborn it is
- How many areas need sealing
- The size of the job
- Whether there’s mould to deal with
Combining jobs into one visit generally 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 price for the lot.
What we need to know
To make quoting easier, please include:
- What the problem is, such as mould, gaps, leaks or cracking
- Whether it has been sealed before
- Roughly how big the job is
- How we’d reach the joints
To get a quote, call 0345 464 0079 or send us an email with the location and a short description of the problem. You will have a clear quote before any work starts.
Walls and rooflines in St Albans
With historic houses such as Batchwood Hall (about 1.5 miles north-west) nearby, there’s older building stock in the area around St Albans as well as newer homes. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material. London and the South East are among the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
If you live in an older home near Church of St. Peter, old and new materials meet at the roofline and walls, which is where sealant earns its keep. For landlords with property near St Albans station, failed wall and movement joints let damp in, so they’re worth checking between tenancies.
St Albans is about 20 miles north-west of London, in Hertfordshire. Homes, rented property, offices and hotels in St Albans can book us for external mastic. The work is guaranteed for a year. St Albans is one of 381 places in Hertfordshire we cover. We also work in London, about 20 miles from St Albans.
Postcode districts we cover here for external mastic: AL1, AL3 and AL4. Whether your property is on Gabriel Square, Jubilee Square and Old London Road or a nearby road, we can help. You will find St Albans on the A414 and B651, which makes it straightforward to reach with everything needed for external mastic. Nearby, we also carry out external mastic in Bernards Heath (1 mile north), Sopwell (1 mile south), St Stephens (1 mile south-west), Marshalswick (1 mile north-east) and Park Street (2 miles south). Further out, we also cover Watford (7 miles south-west), Hemel Hempstead (6 miles west), Stevenage (13 miles north-east), Welwyn Garden City (7 miles north-east), Harpenden (5 miles north) and Hitchin (14 miles north). St Albans is one of the larger places we cover in Hertfordshire.
Near you in St Albans
Around St Albans, our work takes us to homes and buildings near Alban City School, The Horn pub and Verulam School, among other places. St Albans has its own railway station: St Albans station. A little further out are St Albans Musical Museum (0.5 miles north-east) and The Maltings (under half a mile west). Green spaces nearby include The Wick Local Nature Reserve and Verulamium Lake.
Different surfaces, different methods
Cladding and façade panels
Where a cladding system has its own specified sealant, we follow it or an approved alternative. Tell us what the building has when you get in touch.
Concrete and blockwork
Concrete and block walls shrink as they dry and move with temperature. Their movement joints are sealed over backing rod with a flexible sealant.
FAQs for St Albans
I let a flat near St Albans station. Can you help?
Yes, rental work is part of what we do. You can ring 0345 464 0079 or send us an email with the address and a few details, and we’ll give you a fixed price before we start.
Is external mastic in St Albans guaranteed?
All our work, in St Albans and everywhere else, comes with a 12-month guarantee. We’re fully insured, and an ARBOMaster approved applicator.
Do you take out the old sealant first?
Yes, always, and completely. New sealant won’t bond properly to old, so any old material comes out before anything new goes in.
What does external mastic cost?
Size, access and the old material all affect the cost. Call for a quick quote and we will talk you through it.
Will you leave a mess?
No. We work neatly, protect the area around the joints and tidy up afterwards.
What sealant do you use?
Products from Arbo and Everbuild, among others, picked for each joint. We explain the product when we quote.
Can I do it myself?
That depends on the joint. High-level, external movement and fire-rated joints are professional jobs.
Can you work on commercial sites?
Yes. We work in offices, washrooms, hotels and other commercial premises. Working times can be discussed when we quote.
What happens if it’s left?
Done well, a resealed joint is a neat, straight line that suits the wall. A hurried job with smeared edges and no backing looks worse and fails sooner, so it pays to do it properly once. Busy buildings in St Albans, from hotels to offices, cannot afford rooms out of use for leaks or mould, so failing joints are best replaced on a planned basis.
Every job is a little different, so we quote each one individually. Size, access and the product the joint needs all make a difference, and we will explain the quote if you ask.
Why us?
- Any old sealant cut out fully, not covered over
- Anti-fungal silicone where joints get wet
- We leave the area clean and tidy
- Quality sealants from Arbo and Everbuild
See our cost guide or customer reviews.
What sealant work can’t fix
Some problems need a builder, plumber or other trade rather than us:
- Structural movement, which needs a surveyor or engineer
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Failed render or damaged cladding panels
If you are not sure, just ring 0345 464 0079 or email us and we will give you a straight answer.
Joints and surfaces we work on
- Façade panels
- Concrete & block
- Render & cladding joints
- Joints between brick and frames
- Copings & trims
- Brickwork movement joints
How the visit works
A visit follows a simple pattern: we check the joints, protect the area around them, carry out the job and clear up. Most jobs take anything from a few hours to several days, depending on the building. Commercial jobs in St Albans can be planned out of hours where a building can’t close, while home visits are arranged within our normal working hours, Monday to Saturday.
- 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.
- We prime the faces where required.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
How to prepare
- Plan for the work area to be out of bounds to pets and children
- Tell us if parking is tricky
- Tell us about access, such as stairs, a lift or high-level joints
How to get a quote
Want a quote for external mastic? Please phone 0345 464 0079 or send us an email and tell us about the job. You’ll know what we plan to do, and what it will cost, before any work begins.