Managing agents and housing providers see sealant problems as a stream of separate reports: a leak at a window here, a black bead in a communal toilet there, a cracked movement joint on a gable end. Dealing with each one alone is expensive and slow. Treating mastic as a planned, block-wide item is usually better for residents and budgets. This guide explains how to set that up across blocks and estates.
Know what you’re responsible for
Start with the leases, tenancy agreements or title deeds. They set out which joints sit with the landlord, owner or association and which with occupiers. Typically, external window and door perimeters, facade movement joints, communal areas and shared roofs and walls fall to the building owner or factor. Getting this clear early avoids disputes about who pays.
Where responsibility is split, a short note to occupiers explaining which joints they look after, and which the block does, avoids confusion when leaks are reported.
Survey the stock
Build a simple record for each block:
- window and door perimeter joints, by elevation
- movement joints in brickwork, blockwork or cladding
- communal entrances, stairwells and bin stores
- communal washrooms or kitchens
- fire-resisting walls and floors in risers and service cupboards
Note the condition with photos. Rank blocks by urgency: active leaks first, then joints that have visibly failed, then joints near the end of their useful life.
Plan a block-wide programme
Once you know the condition, group the work. Resealing a whole elevation, or a whole block, while access is in place is far more efficient than returning window by window. Build access into the plan: some low-rise blocks can be reached from the ground or with simple equipment, while taller ones need more planning. Schedule external work for the drier months where you can. Our mastic sealing service is set up for block and estate programmes.
Sealant joints are maintenance items. Their life depends on movement, UV and weather, cleaning, traffic and the product, so there is no fixed replacement date. Building joints into a cyclical maintenance plan lets agents spread costs and set realistic service charge budgets. After each phase, keep a record of the joints done, the products and colours used, and the guarantee dates. That history helps the next survey.
Need the work done? Mastic Doctor covers South East England, London and all of Scotland, with a 12-month guarantee on our workmanship. Send details for a fixed quote.
Residents and consultation
Tell residents what is happening and when. Window perimeter work may need short access to flats, or for residents to keep windows closed while sealant cures. For leaseholders, any consultation rules that apply to major works should be followed; take advice on your own obligations. Clear letters and notices reduce missed appointments and complaints.
Older blocks and asbestos
On blocks built or refurbished before 2000, check the asbestos register before old mastic is cut out. Some older sealants can contain asbestos, and you can’t tell by looking. Our guide to asbestos in old mastic explains what to check.
Scotland: tenements and factors
In Glasgow, Edinburgh and other Scottish cities, many residential buildings are sandstone tenements, and managing agents are often called property factors. Common repairs there follow the title deeds and owners’ decisions. Weather in the west of Scotland is wetter than the east, which affects when external work can go ahead (see weather and sealant). We cover all of Scotland as well as the South East and Greater London. Our housing associations and managing agents page has more.
Quick answers
Is it cheaper to reseal a whole block at once?
Usually it is more efficient, because access, set-up and travel are shared across more joints. Send the block details and we’ll give you a fixed quote for the scope.
How often should block mastic be checked?
There’s no fixed interval. It depends on exposure, the product and the building. Many agents include joints in an annual or cyclical inspection and look again after reported leaks.
Can fire-rated sealing be included in the programme?
Yes, where fire-rated sealant is the specified product for the penetrations or gaps. We install it to the manufacturer’s tested detail; design and sign-off sit with the designer and building control.
Related services
- Mastic sealing for building owners and managing agents
- Facade and window perimeter sealing
- Fire-rated sealing and fire stopping
More advice
- Planned Sealant Maintenance for FMs
- Leaks Around Windows on Commercial Buildings
- Asbestos in Old Mastic: What Duty Holders Need
- Building Safety Act and Fire Stopping Records
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.