Na h-Eileanan Siar · Scotland
Knock External Mastic
Sealing brickwork movement joints, render, cladding and façade joints for homeowners, landlords and businesses in Knock. Fully insured, ARBOMaster approved and guaranteed for a year.
- Sealant that has lost its bond to the brick or render
- Failed sealant between panels on a façade
- Movement joints filled with mortar instead of sealant
Common problems we fix in Knock
Sometimes a movement joint was filled with mortar or a rigid filler by mistake. The joint cannot move, so the wall cracks somewhere else instead.
Look out for these signs:
- Failed seals between different materials
- Joints with sealant missing in places
- Water getting into walls through failed joints
- Movement joints filled with mortar instead of sealant
In and around Knock, as anywhere, good external mastic starts with a clean, dry, properly prepared joint.
Before booking anyone
- Which colour the sealant will be
- When the joint can take water or movement
- What the quote includes, VAT included or not
- Is the old sealant removed completely?
About our external mastic in Knock
Getting the depth right is half the job. Backing rod controls how deep the sealant goes and keeps it off the back of the joint, so it bonds to the two sides only and can stretch. We are often asked to deal with weeds or debris growing in open joints and rain getting behind render or cladding at a joint, on copings & trims, façade panels and render & cladding joints.
Across smaller places in Scotland, stone and harled cottages, farm buildings and newer houses often stand exposed to wind and rain. Outside joints on exposed walls work hard, so they need a sealant that moves with the building.
All of our work is guaranteed for twelve months, in Knock and everywhere else we cover.
- Where
- Knock (HS2)
- Wider area
- Na h-Eileanan Siar
- Guarantee
- 12 months on all our work
- Price
- A clear price before work begins
- info@mrmastic.co.uk
- Page updated
- 26 October 2026
Nearby places to Knock
Also in Knock
What we cannot put right
We won’t take on work that will not last, so here’s what sealant can’t put right:
- Movement that is more than a sealant joint can take
- Render that’s blown, hollow or coming away
- Cracking across the wall rather than at a joint
If you are not sure, just send an email to info@mrmastic.co.uk and we’ll give you a straight answer before booking.
Joints and surfaces we work on
- Joints between brick and frames
- Concrete & block
- Render & cladding joints
- Copings & trims
- Façade panels
- Brickwork movement joints
What affects the cost of external mastic
Your quote is based on your job. We take into account:
- Mould in or behind the old joints
- The old material and how stubborn it is
- How many rooms, windows or areas are involved
- Access and height
There are no prices on our website, because each job is priced on what it involves. Call for a quick quote and we will talk you through it.
What to tell us for a quote
When you call or email, it’s useful to know:
- Photos by email, if that is easy
- Where the property is
- How many joints, rooms or windows are involved
- Any previous sealing or DIY work
We do not publish a price list, as no two jobs are quite the same. Instead, we give you a clear price for your job. To get started, drop us a line at info@mrmastic.co.uk.
What happens on the day
All our tools and materials come with us in the van, so there’s nothing for you to buy. Once we have agreed what’s being done, the area is protected and the work begins. It normally takes anything from a few hours to several days, depending on the building. Around Knock, distance and access matter more than parking. Tell us how to find the property and how to reach the work, and the visit is planned around that.
- We start by walking round the building and agreeing the joints and the access.
- We cut out the old mastic and rake out anything in the joint.
- The faces are brushed clean and primed where the product requires it.
- We fit closed-cell backing rod to control the depth.
- The exterior sealant is applied, tooled and checked along its length.
Preparing for the visit
- Let us know about stairs, lifts or work at height
- For business premises, tell us about site rules or sign-in
- Tell us if parking is tricky
Get a quote
If you’re in Knock and need external mastic, drop us a line at info@mrmastic.co.uk. A short description of the job and where it is helps us quote, and you’ll get a clear quote before work begins.
Read more
Why act early in Knock
Sealing over the top of old mastic doesn’t hold for long. New sealant doesn’t bond well to old, weathered sealant, so the old joint is cut out fully first. In an older home around Knock, damp from a failed joint can get into timber and plaster.
Leaving a failed joint normally makes the job bigger, not smaller, as water and mould keep getting in. If you are not sure whether it needs doing, drop us a line at info@mrmastic.co.uk for an honest opinion and a quote.
What you get with us
- Trusted Arbo and Everbuild sealants
- Anti-fungal silicone where joints get wet
- White, clear, grey or coloured to suit, where the product allows
- 20+ years of sealant experience
See our cost guide and what customers say.
Knock questions
Is Knock in your area for external mastic?
Yes, Knock is within the area we cover. Our work covers the whole of Scotland. You can send an email to info@mrmastic.co.uk and tell us what needs doing, and we will send you a clear quote.
Does living near the coast affect external mastic in Knock?
Coastal homes put outside sealant through more weather than inland ones, so the choice of sealant and the preparation matter even more. It’s worth checking the walls that face the sea first.
Can you seal over the old sealant?
No, because it fails. The old sealant always comes out first, so the new joint bonds to clean surfaces.
Is there a guarantee?
Yes. Every job comes with our 12-month guarantee.
Can I do it myself?
For a simple, easy-to-reach joint, a careful DIYer can do a reasonable job. Most DIY failures come from sealing over old material, wet joints or too much sealant.
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. Brands we use include Arbo and Everbuild.
Can you seal joints between render and window frames?
Yes. The old joint is removed, both surfaces cleaned and primed where needed, and a flexible sealant applied. The colour is chosen to suit.
Do you work for hotels and businesses?
Yes. Hotels, offices and other businesses use us and we’re fully insured.
Knock buildings and the weather
Knock is within about 1 mile of the coast, where wind-driven rain is a fact of life and, nearer the shore, so is salt air. Both are hard on movement joints and outside wall joints, which can dry out and crack sooner where a building faces the weather. Work on the islands has to be planned around ferry crossings and the weather, so the more notice, the better.
For jobs in and around Knock, choosing the right material for each joint is as important as a tidy finish.
Knock (Gaelic: An Cnoc) is in Na h-Eileanan Siar. Whether you are in the middle of Knock or further out, external mastic is available for homes and businesses alike. We cover 87 towns and villages across Na h-Eileanan Siar, large and small.
Postcode districts we cover here for external mastic: HS2. Whether your property is on Seaview and A' Chnuic or a nearby road, we can help. Knock is on the A866, so it’s easy for us to get to with everything needed for external mastic. Close by, we work in Na h-Eileanan an Iar (1 mile west), Aiginis (1 mile west), Lower Bayble (1 mile east), Garrabost (2 miles north-east) and Pabail Uarach (2 miles east). Island and remote addresses take a little more planning, so tell us where you are when you ask for a quote.
What’s near Knock
A little further out are Western Isles Hospital (4.5 miles west).
Work for landlords, hotels and businesses
We regularly work with letting and managing agents. Tell us the address, the job and how access works.
From a single let to a portfolio, the work is the same standard: old sealant fully removed, joints prepared properly and a one-year guarantee.
How the job changes by surface
Joints between dissimilar materials
Wherever two materials meet, they move differently. A flexible sealant bridges the two so neither cracks the other.
Cladding and façade panels
Metal and composite panels move a lot with temperature, so the joint sealant has to cope with frequent movement. We choose the product to suit.