Greater London · England
Sand mastic for sash & case windows in Forest Hill, Greater London
Specialist sand mastic for Forest Hill: careful preparation, the right product and tidy work. Ask us for a quick quote.
- Patchy fillers round a sash window
- Draughts and rain around sash boxes
- Mastic round period door frames that has failed
What we do, step by step
There is not much for you to do on the day. Show us the job and we will take it from there. The job generally takes a few hours per window, depending on the condition of the joints from start to finish. In Forest Hill, as in most of London, parking needs a little planning. A visitor permit or a nearby bay makes the visit run more smoothly.
- We start by checking each surround and agreeing the joints to renew.
- Old, loose mastic is raked out and the joint cleaned.
- We pack any deep gaps so the mastic sits at the right depth.
- The mastic is mixed, pressed into the joint by hand and shaped.
- The mastic is finished to sit tidily against the stone or brick.
Before we arrive
- Tell us about any water getting in
- Where the joints are inside, avoid wetting them before we arrive
- On commercial sites, let us know about site rules
How to get a quote
There’s no standard price list, as no two jobs are quite the same. Instead, we send you a clear quote for your job. To get started, ring 0345 464 0079 or email us.
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Sand mastic in Forest Hill
Across Forest Hill, we renew sand mastic around sash and case windows. Every joint is cleaned out and filled by hand, finished to suit the masonry. If you are dealing with a silicone bead on a sash window that spoils the look and tired mastic found when preparing windows for paint, we can put it right, on brick reveals, period & listed homes and sash and case windows alike.
Many London homes are flats, with windows high above the street. In a converted house or block, the lease generally says who is responsible for the windows, so it’s worth checking before booking.
We stand behind the work with a 12-month guarantee, so you are covered after we have gone.
- Location
- Forest Hill (SE23, SE22, SE26)
- Region
- Greater London
- Guarantee
- 12 months on all our work
- Quote
- A clear quote up front
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
What affects the cost of sand mastic
Call for a quick quote. What matters most is:
- Any working-time requirements on site
- Whether there’s mould to deal with
- How many rooms, windows or areas are involved
- The number and length of the joints
What it costs depends on the size of the job, how much old material has to come out and access to the work. You will have a clear quote before any work starts.
Asking for a quote
You do not need to know the technical terms. It helps if you can tell us:
- Where the property is
- Photos by email, if that’s easy
- The problem you’ve noticed
- Whether it has been sealed before
For sand mastic in Forest Hill, call 0345 464 0079 or email us. Tell us what the problem is and where, and we will agree the price before any work begins.
Forest Hill questions
Can you help a landlord with a rental near Honor Oak Park station?
Yes, landlords and agents are among the people we work for. You can phone 0345 464 0079 or email us with the details for a clear quote.
Can you do sand mastic in Forest Hill?
Yes. We work across London and the South East, and Forest Hill is part of that. You can phone 0345 464 0079 or drop us an email and tell us what needs doing, and we’ll send you a clear quote.
Do you take out the old sealant first?
Yes, every time. New sealant will not bond properly to old, so any old material comes out before anything new goes in.
Is sand mastic better than silicone for my windows?
It depends on the window. Period windows in stone or brick normally suit sand mastic, while modern frames normally get a flexible sealant.
Do you work for hotels and businesses?
Yes, regularly. We can plan bigger jobs in stages to suit the site.
Is it possible to paint over sand mastic?
Sand mastic is normally left unpainted, as guidance on traditional windows advises. Talk to us before any painting near it.
How long does sand mastic take to harden?
It skins over fairly quickly but takes longer to harden fully. We’ll tell you what to expect for your job.
Do you offer different sealant colours?
We help you choose a colour that suits, from white and clear to greys and other shades. The product needed can limit the range.
Also near Forest Hill
Also in Forest Hill
Frames and glazing around Forest Hill
In London conversions and blocks, the lease decides who is responsible for the frames, so check that before you book. Historic houses like Kingswood House (about 1.6 miles south-west) are a reminder that the area around Forest Hill has older buildings as well as new. Where a home is older, older timber frames in brick or stone need a different approach from a modern uPVC window.
If you look after a building such as Fairlawn Primary School, larger buildings have plenty of frames, and the mastic around each one ages. Forest Hill is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Forest Hill is about 2 miles south-east of East Dulwich, in Greater London. Our applicators cover sand mastic for homes and businesses in Forest Hill and nearby, as part of our work across Greater London. 764 places in Greater London are on our list, large and small.
Work in SE23, SE22 and SE26 works the same way as everywhere else we cover. If you need sand mastic at a property on Ewart Road, London Road and Rojack Road or anywhere close by, we can help. Other places close to Forest Hill include Honor Oak (1 mile north), Perry Vale (1 mile south-east), Brockley (1 mile north-east), Crofton Park (1 mile north-east) and Dulwich (1 mile west). Larger places within reach include London (4 miles north-west), City of Westminster (6 miles north-west), Marylebone (6 miles north-west), Kensington (7 miles north-west), St Pancras (6 miles north-west) and Shoreditch (6 miles north).
Around Forest Hill
We work in homes and buildings around Allenby Tutorial Trust, Capitol Cinema pub and Harris Girls' Academy East Dulwich and the streets around them. The nearest railway station is Honor Oak Park station, about 0.5 miles north-east of the centre. Well-known places in the area include Greenwich Castle (3.1 miles north-east) and Horniman Museum and Gardens (0.5 miles south-west). Green spaces nearby include One Tree Hill and Knight's Hill.
How the job changes by surface
Tenement and terrace windows
Upper-floor windows need access planning. Tell us the height and we will confirm what’s needed.
Period and listed homes
Period homes look their best with traditional materials.
Why it’s worth doing now in Forest Hill
Filling over old, loose mastic doesn’t last. Raking out and preparing the joint gives it a sound base so the new work lasts. In a London flat, a failed joint rarely stays your problem alone: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
The cost reflects the work involved, not a rough estimate. That’s why we ask a few questions first.
Why book with us
- We never seal over old sealant
- Trusted Arbo and Everbuild sealants
- We are fully insured
- More than 20 years in sealant work
Take a look at how sealant jobs are priced or what customers say.
Common problems we fix in Forest Hill
Age is the main cause. Even well-laid mastic needs renewing in time, depending on exposure and upkeep.
The most common problems we see are:
- Modern sealant on a period surround
- Window mastic to renew ahead of painting
- Old sand mastic that has cracked, crumbled or fallen out
- Weathered mastic on the most exposed windows
If you live in an older home near Honor Oak Christian Fellowship Centre, the joint between an old wall and a newer frame is usually the first place rain gets in.
What your quote should include
- What insurance they hold
- Whether all the old sealant comes out first
- What happens if they find a problem under the old sealant
- Whether you can choose the colour
Aftercare tips
Good habits help new joints last longer. Our tips:
- Go gently near the mastic when preparing windows
- Ask a joiner to look at soft timber first
- Ask us before painting near the mastic
- Check the mastic when you check the paintwork
Do not touch or press the mastic while it hardens. It skins over quickly, but takes longer to harden fully.
Fine cracks show the mastic is starting to fail. It’s easier to renew it before it drops out.
DIY sealant or a professional job?
A DIY attempt doesn’t rule out a professional job. We remove it and do the joint properly.
If you do try it yourself, take your time over the preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it does not work out, we can still put it right.