Hertfordshire · England
External Mastic in Lemsford
External mastic across Lemsford and nearby, with every bit of old sealant taken out first.
- Plants rooting in failed movement joints
- Leaking joints around cladding and façade panels
- Movement joints filled with mortar instead of sealant
How to look after the new joints
To keep the joints looking good and working properly:
- Have failed joints looked at early
- Check the sealant is paintable before painting near it
- Walk round the building once a year and look at the joints
- Point out the joints to other trades
Keep the joints clear of soil, plants and climbing growth. Anything that holds water against the joint wears it out sooner.
Act while the splits are small. Then it’s a straightforward cut-out and reseal.
External mastic in Lemsford, done properly
Joints in render and cladding are easy to overlook until a damp patch appears. We inspect them, agree which need doing and reseal with a weatherproof, flexible sealant in a colour to suit. If you are dealing with leaking joints around cladding and façade panels and water getting into walls through failed joints, we can put it right.
Somewhere as small as Lemsford, homes and farm buildings often face open ground, where walls and rooflines take the weather head on. Gutter joints and wall joints there need a sealant that can flex and stay put.
You’re covered for a year from the day we finish. If anything isn’t right with it, call 0345 464 0079 or send us an email.
- Where
- Lemsford (AL8)
- Region
- Hertfordshire
- Guarantee
- 12 months on all our work
- Price
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
Surface by surface
Concrete and blockwork
Wide joints in concrete need the depth controlling carefully. Backing rod sized to the joint sets it and keep the sealant to the right depth.
Brickwork movement joints
Brick walls have vertical movement joints to absorb expansion. They’re resealed over backing rod with a low-modulus sealant in a colour to suit the brick.
What we’re called out for in Lemsford
Poor preparation causes many early failures: joint faces that were dusty or damp, unprimed where they needed it, or still carrying old sealant. The sealant never bonds properly.
The problems people normally mention when they call include:
- Failed seals between different materials
- Rain getting behind render or cladding at a joint
- Hard, crazed mastic that has stopped moving
- Leaking joints around cladding and façade panels
In the older streets around Church of St John the Evangelist, old and new materials meet at the roofline and walls, which is where sealant earns its keep.
Comparing quotes
- What the cure time is
- How much experience the applicator has
- How hidden problems are handled
- Is VAT in the price?
What we do, step by step
We work through the job in order: protection first, then preparation, sealing and a tidy-up. Typically it takes a few hours for a handful of joints, longer for a whole elevation and we leave things clean and tidy. In a small place like Lemsford, access is generally the main thing to plan. For outside work, also let us know about exposed walls and any outbuildings involved.
- Each joint is checked and the colour of the new sealant agreed.
- We take out the old sealant until the faces are sound.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
Before we arrive
- Plan for the work area to be out of bounds to pets and children
- Mention any sign-in or site rules at work premises
- Clear items away from the joints we’re working on
How to get a quote
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is. When it suits you, phone 0345 464 0079 or email us.
Read more
Places near Lemsford
Other services in Lemsford
What external mastic looks like in Lemsford
Historic houses like Digswell House (about 1.9 miles north-east) are a reminder that the area around Lemsford 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. 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.
For site and facilities teams at buildings such as Applecroft School, larger buildings have long runs of movement joint that eventually need resealing. For landlords with property near Welwyn Garden City station, outside joints that have cracked can let damp into a rental, so check them between lets.
Lemsford is about 2 miles west of Welwyn Garden City, in Hertfordshire. Lemsford gets the same service as everywhere we cover: old sealant removed completely, careful preparation and a 12-month guarantee. Lemsford is one of 381 towns and villages in Hertfordshire we cover. London is on our list too, about 21 miles from Lemsford.
We cover every part of AL8 for external mastic and the streets around it. If you need external mastic at a property on Mill Close, Lemsford Village and Great North Road or a nearby road, we can help. We also cover the places around Lemsford: Stanborough (1 mile south), Coleman Green (2 miles west), Cooper's Green (2 miles south-west), Hatfield (2 miles south) and Smallford (3 miles south-west). Further out, we also cover Watford (12 miles south-west), Hemel Hempstead (10 miles west), Stevenage (8 miles north), St Albans (5 miles south-west), Harpenden (5 miles west) and Hitchin (11 miles north).
Near you in Lemsford
We work in homes and buildings around Stanborough Park, Stanborough School and The Sun Inn. For rail, the closest station is Welwyn Garden City station, about 1.2 miles east. Well-known places in the area include Queen Elizabeth II Hospital (2.1 miles south-east) and The Bunker at Hatfield Police Station (2.1 miles south). Open spaces near Lemsford include Lemsford Springs.
Landlords, agents and businesses in Lemsford
Letting agents and landlords in Lemsford can book us as well as homeowners. Sealant work between tenants keeps a property looking cared for before the next move-in.
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements and we’ll quote.
Common questions in Lemsford
Is Lemsford within the area you cover?
Yes. Lemsford is within the area we cover, which takes in towns, villages and rural addresses. Our work covers London and the South East. Let us know about access, parking and anything unusual about getting there when you book.
Do you work for landlords with property near Welwyn Garden City station?
Yes. We work for landlords and agents as well as householders. You can ring 0345 464 0079 or drop us an email with the details for a clear quote.
Do the sealants smell?
That depends on the sealant. Some products have a noticeable smell, others very little, and any smell fades as they cure.
Do you work for hotels and businesses?
Yes. Commercial and hotel work is a large part of what we do, as well as homes. We can talk about working times when we quote.
Should I point up the gap in my brickwork?
No. Rigid materials cannot move with the wall. Where a joint has been mortared, it can often be raked out and sealed properly.
Can you do several jobs on one visit?
Of course. Combining jobs makes good use of the visit, so mention them when you ask for a quote.
How long does the job take?
As a guide, most jobs take a few hours for a handful of joints, longer for a whole elevation. Bigger jobs take longer.
Are you insured?
Yes. We are fully insured for domestic and commercial work.
Leave it or put it right?
The longer a joint stays open, the more water the wall takes in. In cold weather, frost can damage wet brick and render near the open joint, so the damage spreads beyond the joint. Older cottages and farmhouses around Lemsford can have timber floors and frames, where water from a failed joint can cause rot if it’s left.
Every job is a little different, so we quote each one individually. Size, access and the product the joint needs all play a part, and we will explain the quote if you ask.
What you get with us
- Sealant colour chosen to suit
- 180+ five-star Google reviews
- Over 20 years’ experience
- We never seal over old sealant
Read our cost guide or our reviews.
Can I do it myself?
Some sealant jobs are within reach of a careful DIYer, like a short, easy-to-reach joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
If you are set on DIY, put the effort into preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it fails, we can still redo it.