Cast in Situ

Cast in Situ concrete lining

The cast in Situ concrete lining is one of the longest lasting linings in the industry as long as it is carried out correctly. This type of lining has a life expectancy of 60 years.

This is a Brief outline of the Technique.

  • Arrive at the property, erect ladders on roof and temporary access platform around chimney
  • Inside the property we cover all furnishing as required using new plastic and dust sheets, block chimney in preparation for cleaning.
  • Clean chimney with wire chimney brushes. If a build up of tar is encountered we would possibly use a Flail (spinning chain) for removal.
  • When this action is completed and all debris is cleared, a rubber tube (Void Former) is inserted into the length of the chimney (Like a long tube and inflated with compressed air to the required diameter, you then have a former for the insulated concrete.
  • Holes are required at intervals to space out and centralize the former, on long curved bends a number of holes may be required to ensure an even infill is achieved (As Photo) – this is an important part of the installation.
  • The compound is then mixed on site using a volcanic dust, Portland cement and water to the right consistency,
  • This compound is then pumped around the Void former (tube) from the base of the chimney to the top of the Chimney stack,
  • The monitoring of the filling is carried out at all times so there is an even infill around the former (Tube)
  • The holes are filled in with Masonry as the compound reaches each hole,
  • When the chimney is filled to the top of the chimney stack it would then be left for a period of time to harden,
  • The former is then removed leaving a smooth circular flue which is insulated and leak proof,
  • All holes are made good on completion, No allowance is made for decoration.
  • This type of lining generally takes a Day to set up and fill the chimney, The former is generally left overnight for the material to harden, A return journey would be made to    remove  the former, Fit chimney pot and plaster the access holes.
  • If the lining is for a Solid fuel open fire a gather would have to be formed in the chimney throat area.
  • Solid fuel stoves would have a Sump adaptor fitted at the base of the lining to deflect any moisture etc into the flue pipe.
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Concrete pump for cast in situ

Putzmeister P11 for mixing and pumping compound

Void former in chimney

Former (Tube) down chimney

Additional spacers

Spacing out the former

Pumping concrete

Filling chimney

Filling chimney

Filling chimney

A number of holes may be required on a bend

A number of holes may be required on a bend

Mix ready for pumping

Mix ready for pumping

Finished lining

Finished lining

Access platform

Access platform


© Chimneyline 2010