What is a cast in situ chimney lining?
The Cast in Situ concrete lining system is one method of lining a domestic chimney. An inflatable rubber former is inserted into the flue and pressurised until it reaches the diameter required for lining. Temporary openings are made to insert spacers to centralize the rubber former. Once the rubber former is centralised the void around it is then filled with an approved and tested mix of perlite, cement and water all the way up.
The temporary openings are filled as the mix reaches each hole. All the holes are made good with plaster once works are complete. The mix is then left to harden overnight.
The former is then deflated and removed leaving a perfectly insulated and leak proof flue. When correctly installed the chimney lining has a life expectancy of 60 years. The first hole is generally knocked in the breast (not in every case). The second hole would be in the room above (generally the bedroom). A third would be in the loft (Attic).
The rubber former (tube) is lowered down the chimney and pressurised until it reaches the required diameter. The former is spaced through the access holes to give an even supply of mix. The mix is pumped around the rubber former making sure it is spaced correctly.
A number of temporary holes may be required in sharp bends. When the mix reaches a hole these are then blocked with bricks or stone and plastered on completion.