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Handy How to Guides

Installation Guidelines for Schiedel Pumice & Ceramic Liners
Installation Guidelines for Pumice & Ceramic Liners

Please always refer to the appropriate Schiedel Installation Guides for the system/flue that is being fitted.

Flue linings and components should be installed in accordance with the requirements of Approved Document J of the Building Regulations.

Check that the appropriate flue linings to suit the intended appliance or open fire are to be installed.

All flue linings and components should be examined before installation and any damaged items should not be used.

Flue linings are to be installed with the socket uppermost and jointed with the appropriate Schiedel fireproof mortar/sealant, Lip Glue for pumice and Rapid for ceramic.

Joints should be fully sealed and pointed; any surplus sealant protruding into the flue should be removed during construction.

Excessive lip glue on installation.jpg

Example of excessive lip glue applied during installation and not being cleaned throughout the chimney construction.


Another example of excessive lip glue. Soot can build up on the ridges and lead to chimney fires.

Excessive Lip Glue (2)_edited.jpg


If using pumice or ceramic flue liners the gap between the flue linings and the surrounding masonry should be at least 15mm. These gaps should be filled with Schiedel Leca Insulation mixed 20:1 with ordinary Portland cement (20 parts Leca to 1 part OPC) and mixed with a small amount of water.

Only factory made components should be used to form bends or offsets. If using the Isokern pumice liner system then liners can be cut between bends to suit. Lip glue and steel collar must be used to seal the joint. All offsets must be adequately supported.

Flue construction should be protected against exposure to rain and at the end of each day until the mortar/sealant has fully hardened.

Perform checks to ensure that the internal flueway is clear of any protrusions or obstructions and remove any excess fireproof mortar/sealant, cement mortar and debris

Smoke Testing During Construction
Smoke Testing During Construction

The purpose of smoke testing is to check that the flue gases will rise freely up the flue and to identify any possible faults, such as incorrectly sealed joints, damaged components and/or obstructions in the flue.

If the flue components have been inspected and the installation checked as work proceeds it may not be necessary to carry out the smoke test. However, if there are any doubts as to the integrity of the flue, carry out the following smoke test, based upon the recommendations given in Approved Document J of the Building Regulations.

Smoke Testing on Completion
Smoke Testing on Completion
Visual Inspection
Smoke Test Procedure
Coring Ball Test

Before carrying out the smoke test the following visual inspection should be made to ensure the installation is correct and complete:

Visual Inspection

Check that the appropriate products have been correctly installed and all joints have been sealed with Schiedel mortar/sealant.

Check that the internal flueway is unobstructed , complete and continuous throughout its length and remove any excess joining material, mortar or debris.

Check that the necessary distance from combustible material (timbers) has been provided and require terminal is correctly sited as required by building regulations.

Smoke Test Procedure

Close all doors and windows in the room served by the flue.

Warm the flue for up to 10 minutes using a blowlamp or similar to establish a flue draw. A longer warming up period may be required when testing larger flue sizes and in the case of wet or cold flues.

Place two or more smoke pellets on a masonry block stood on end within the fire opening or recess and ignite.

When the smoke is seen to steadily exit from the top of the flue or terminal, seal off the top using an inflatable bladder or plastic bag placed over the terminal and sealed around the edges.

Check the full length of the flue/chimney construction for any significant leakage. This includes checking for smoke leakage around window openings and cavities when the chimney is built in as part of a cavity wall.

The test should be allowed to continue for at least 5 minutes and is considered satisfactory if there is no significant leakage of smoke through the walls of the flue. if significant leakage does occur the cause should be investigated and rectified, followed by repeating the test. A strong plume of smoke escaping through a joint or defect would be considered as a major leakage.

Always follow the manufacturer's safety instructions when using smoke pellets and take the necessary protection to avoid inhalation of the smoke.

Once the flue has satisfied the test, ensure the closures at the top and bottom of the flue are removed.

Coring Ball Test

Both Schiedel and FuelSmart DO NOT recommend this type of test as if not done correctly and carefully it can cause permanent flue damage. If any blockage needs removing we recommend this is done using the appropriate chimney sweep brush.

Use & Maintenance
Use & Maintenance

The chimney should be left for at least 72 hours before use, then start with only small fires for the first week and gently increase thereafter.

The chimney should be swept at least twice a year, once before the heating season, once after the heating season and during depending upon use. We recommend using a medium density polypropylene bristle brush of the same diameter as the flue. Steel brushes MUST NOT be used to sweep Isokern Pumice Flues.

Always follow the appliance manufacturer's operating instructions. Avoid burning unseasoned or wet wood and slow burning (slumbering) as this can produce excessive soot and condensation which can cause soot fires and damage.

Chimney Notice Plate

When your pumice chimney parts arrive, you should also receive the Chimney Notice Plate. Keep it safe! You will need it at the end of the construction of the chimney.

Chimney Notice Plate
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