Encapsulation means sealing asbestos containing material in place so that it cannot release fibres, rather than taking it out. It is a recognised and often preferable answer for material in good condition, because removal is itself a disturbance and the moment of highest risk. It is not a way of forgetting about the material: an encapsulated item stays on the register, keeps its re-inspection interval, and has to be pointed out to anybody working near it.
What encapsulation involves
Depending on the material it may be a coating applied over the surface, an impregnating sealant, or a physical enclosure such as boarding over. The point is that the surface can no longer shed fibres and cannot be casually damaged. For sprayed coatings and lagging this is specialist licensable work; for a cement roof or a textured ceiling it is often straightforward.
When it is the better answer
When the material is in good condition, when it is not in the way of planned work, when removal would mean stripping out large parts of a working building, and when the alternative is a poorly executed removal. Encapsulating a sound textured ceiling by overboarding is quicker, cheaper and safer than scraping it, and it produces no hazardous waste.
When it is not
When the material is already damaged or friable, when the building is being refurbished or demolished so the work will reach it anyway, and when the material is somewhere that will keep being disturbed. Sealing a ceiling that a contractor will drill through next year defers the problem into somebody else's hands.
What you owe afterwards
The register records that the material is still there and now sealed, with the date and what was done. The risk assessment is reviewed, a re-inspection interval is set for the encapsulation itself, and every contractor working near it is told. Encapsulation without a record is how a building loses track of what is behind its own walls.
Questions people ask about asbestos encapsulation
Is encapsulation cheaper than removal?
Usually, and it also avoids the hazardous waste and the disruption. The saving is real, and it comes with the obligation to keep managing what is still there.
Can any asbestos be encapsulated?
Material in good condition and unlikely to be disturbed is the candidate. Damaged, friable or crumbling material is normally a removal question, and sprayed coatings and lagging are licensable work either way.
Does encapsulated asbestos have to be declared when selling?
There is no duty to remove it, and a buyer's surveyor will normally ask. Handing over the register and the encapsulation record is the straightforward answer and it usually helps rather than hinders.