Hertfordshire · England
Childwick Green External Mastic
External mastic in Childwick Green from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Failed seals between different materials
- Brick movement joints where the sealant has split
- Water getting into walls through failed joints
Work for landlords, hotels and businesses
In hotels, rooms out of use cost money, so the work can be planned room by room. We have worked in hotels as well as homes and businesses.
Landlords and agents in Childwick Green can book us as well as householders. Sealant work between tenants keeps a property looking cared for before the next move-in.
How we handle external mastic in Childwick Green
Where two different materials meet, such as brick and render or blockwork and metal, they move at different rates. A flexible exterior sealant takes up that movement where mortar or filler would crack. Typical jobs include cracked joints where brick meets render or frames and sealant pulling away from one side of the joint, across copings & trims, render & cladding joints and concrete & block.
In a village or hamlet like Childwick Green, 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.
All our work is covered by a 12-month guarantee.
- Place
- Childwick Green (AL3)
- Wider area
- Hertfordshire
- Guarantee
- 12 months on all our work
- Price
- A clear quote up front
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
Childwick Green questions
Can you help a landlord with a rental near Harpenden station?
Yes, rental work is part of what we do. Just phone 0345 464 0079 or drop us an email and tell us about the property, and we’ll send you a clear quote.
Do you cover smaller places like Childwick Green?
Yes. Childwick Green is within the area we cover, which takes in towns, villages and rural addresses. Our work covers London and the South East. Just mention lanes, gates or anything else about the route when you book.
How long before the joint can be used?
That depends on the sealant used, so please follow the time we give you.
Do I need to be at home?
We need access to the joints, so we’ll agree that with you when we book. For inside work, that normally means someone being in.
What colours does the sealant come in?
Exterior sealants are made in a range of colours, from greys and browns to whites and stone shades. We pick the one that suits your wall best so the joint does not draw the eye.
What do you need from me for a quote?
A short description and the location, plus pictures if you have them. If we need more, we’ll ask.
Do you hold any approvals?
Yes. Mr Mastic is an ARBOMaster approved applicator.
Should I try DIY first?
It depends on the job. Work at height, movement joints, fire-rated gaps and large areas are best left to a professional, while a short indoor joint may be within reach.
What we do, step by step
We work through the job in order: protect, prepare, seal, tidy. For most jobs that takes anything from a few hours to several days, depending on the building. Somewhere as small as Childwick Green, access is often the only tricky part. If the job is outside, mention outbuildings, exposed walls and how to reach them.
- We look at every joint and agree a colour to suit the wall.
- 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.
Getting ready for the visit
- For indoor joints, keep the area dry beforehand if you can
- On commercial sites, let us know about site rules
- Let us know about stairs, lifts or work at height
How to get a quote
The more we know about the job, the more useful the quote. Let us know the location, the problem and roughly how many joints, and email photos if that is easy.
Read more
What we’re called out for in Childwick Green
If plants are growing out of a joint, the sealant has normally failed or was never there. Roots and dirt hold water against the wall and speed up the damage.
If you can see any of these, it’s time to have the joints looked at:
- Old sealant gone brittle and cracked
- Failed seals between different materials
- Brick movement joints where the sealant has split
- Plants rooting in failed movement joints
Managing a site like Townsend Church of England School? Then its movement joints, gutters and trims need looking after like any other building’s.
Before you book anyone
- Whether they seal over old material or remove it
- Who does the work, and how experienced they are
- When the joint can take water or movement
- How the joint is cleaned and prepared
Keeping the joints in good condition
Joint life depends on how it’s used and looked after. We suggest:
- Tell anyone working on the walls about the movement joints
- Avoid pressure-washing directly into sealant joints
- Look over the joints every year, ideally after winter
- Clear growth from the base of walls and joints
Only paint over the joint if we’ve confirmed the sealant can take paint. Paint can crack on a flexible joint and spoil the finish.
Once a joint cannot move, the wall finds another way, usually as cracking in the brickwork or render nearby. Catch it early and you reduce the risk.
External mastic in Childwick Green: local notes
Rainfall in the South East is lower than in much 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 Childwickbury Manor (about 0.4 miles south-west) nearby, there’s older building stock in the area around Childwick Green 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.
If you let a flat or house near Harpenden station, failed wall and movement joints let damp in, so they’re worth checking between tenancies. If you live in an older home near Church of St Mary, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Childwick Green is about 2 miles south of Harpenden, in Hertfordshire. We carry out external mastic for homes and businesses in Childwick Green and nearby, as part of our work across Hertfordshire. We cover 381 towns and villages across Hertfordshire, from the larger towns to small villages. London is on our list too, about 22 miles from Childwick Green.
Work in AL3 is quoted and booked the same way as anywhere else. Whether your property is on Childwick Green and School Lane or a nearby road, we can help. We also cover the places around Childwick Green: Ayres End (1 mile north-east), Bernards Heath (2 miles south), Sandridge (2 miles east), Marshalswick (2 miles south-east) and St Albans (2 miles south). We also work in nearby towns such as Watford (9 miles south), Hemel Hempstead (5 miles south-west), Stevenage (11 miles north-east), Welwyn Garden City (7 miles east), Hitchin (12 miles north) and Hoddesdon (14 miles east).
Around Childwick Green
In Childwick Green, that means homes and buildings near Three Horseshoes Public House and Margaret Wix Primary School. For rail, the closest station is Harpenden station, roughly 2.1 miles north of the centre. Well-known places in the area include Harpenden Museum (2 miles north) and Village Arcade St Albans (2.3 miles south). For a walk, there’s Verulamium Lake and Grebe House Wildlife Garden.
Should I try it myself first?
Too much sealant is as bad as too little. A thick, smeared bead looks untidy and doesn’t move well, and getting the depth right matters as much as the look.
Not every job suits DIY: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
Honest limits
Honest advice matters more to us than a booking, so here’s what new sealant will not do:
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Render that’s blown, hollow or coming away
- Structural movement, which needs a surveyor or engineer
If in doubt, ring 0345 464 0079 or send us an email and we’ll say what we think.
Surfaces we seal
- Joints between brick and frames
- Concrete & block
- Brickwork movement joints
- Copings & trims
- Façade panels
- Render & cladding joints
What affects the quote in Childwick Green
We don’t publish a price list, because no two jobs are the same. What we look at:
- The type of sealant required
- How many rooms, windows or areas are involved
- How much there is to do
- How easy the joints are to reach
A few things move the cost up or down: how much old sealant there is and how stubborn it is, whether mould needs treating, and whether the work is at height. We take all of that into account in your quote.
What we need to know
To make quoting easier, let us know:
- Photos by email, if that is easy
- If it’s domestic, commercial or a hotel
- The rough size of the job
- Whether it has been sealed before
Need a quote? Please phone 0345 464 0079 or email us with a few details. You will know what we plan to do, and what it will cost, before any work begins.