Asbestos (A.C.) sheet roof sealing without replacing sheets
Cemented asbestos roofing sheets crack at the fastener holes and lift at the overlaps long before the sheet itself fails. We seal both, then coat the whole roof — no sheet replacement, no drilling into the cement.
Before · cracked, unsealedAfter · sealed and coated
Sheet overlap joint, drag to compare
Asbestos sheet waterproofing in Karachi
What actually happens when an A.C. sheet roof gets sealed
Asbestos sheet waterproofing in Karachi exists because cemented A.C. roofing sheets usually crack at the fastener holes and lift at the overlaps years before the sheet material itself gives out — replacing sound sheets at that point is wasted cost. Zem Chemicals seals both failure points without drilling into the cement or swapping a single sheet: hairline cracks sealed individually, every overlap resealed with reinforced tape, then a full-surface coating applied across the roof. It's the same overlap-sealing approach used next door on G.I. sheet roofs in the same industrial estates — recent work includes 9,400 sq.ft at Hassan Textiles in New Karachi Industrial Area, handed over in 14 working days. See more completed asbestos sheet waterproofing jobs or send us your roof's covered area for a written quotation.
The problem
Where A.C. sheet roofs actually fail
Hairline cracks radiating out from every fastener hole
Lifted overlaps letting water track sideways under the sheet
Brittle, weathered sheet surface that has lost its original seal
Efflorescence and staining on the ceiling below
Sheets with years of structural life left, but no longer shedding water
The treatment
The treatment we apply
Fastener holes and hairline cracks sealed individually before the field coat
Every overlap resealed with reinforced tape
Full-surface coating applied without drilling into or disturbing the cement sheet
Ridge and valley junctions detailed before coating
Sections re-checked for seepage where roof access allows
How the job runs
Four stages, in this order, every time
Skipping a stage is how a waterproofing job fails in year two. This sequence is not negotiable on our sites.
Survey
Sheet-by-sheet inspection
We check every sheet for structural condition before quoting — a sheet that has failed structurally gets flagged for replacement, not coated over.
Preparation
Crack and fastener sealing
Every fastener hole and hairline crack sealed individually, without drilling into the cement sheet.
Application
Full-surface coat
Coating applied across the whole roof so ageing sections are protected along with the damaged ones.
Handover
Warranty and job sheet
Sections checked for remaining seepage, then written warranty.
Questions we get asked
Asbestos sheet waterproofing — the practical answers
Is it safe to work on asbestos sheet roofs?
Yes — our treatment coats and seals the existing sheet without cutting, drilling or disturbing the cement, which is where any asbestos fibre risk would come from. Nothing is ground down or removed.
Do you drill into the sheets?
No. Fastener holes and cracks are sealed from the surface, not re-drilled or enlarged.
How long did the Hassan Textiles job take?
9,400 sq.ft of cemented asbestos sheet roof at their New Karachi Industrial Area unit was completed in 14 working days.
Can this be combined with heat-proofing?
Yes. The same reflective top system used on our roof heat proofing service can be applied over this treatment.
