Chimneys and parapets
New sand-and-cement flaunching sits on an old stack and is already cracking. What flexibility has that hard mix not given the pots?
That hard sand-and-cement mix has not given the pots any flexibility. New flaunching sits on an old stack and is already cracking, which is what a rigid crown often does when pots and masonry move with heat and weather. The survey has seen fresh hard mortar that has cracked. It has not said the stack is leaning, has not tested the flues, and has not treated the cracks as proof that the pots are loose.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Flaunching is the mortar that beds the pots and sheds rain off the top of the stack. A sand-and-cement mix can be strong and brittle. An old stack and clay pots expand and shrink; a hard cap does not follow them, so cracks open early. Those cracks can let water into the head of the chimney. They are a fault in the new mix, not a measurement of lean and not a flue test. The pots may still be seated. The survey did not pull them to find out.
Ask a chimney contractor to cut out the cracked hard flaunching and to bed the pots in a mix that can tolerate movement, if that is the repair they recommend. Tell the solicitor the note is the new crown, not a leaning stack and not a condemned flue. The survey has not specified the replacement mix in detail and has not investigated the flue lining. Keep those later decisions with the contractor.
What should you ask your surveyor?
- Is the cracking in new sand-and-cement flaunching on an old stack?
- Have the pots been left untested for movement?
- Did you record a rigid mix rather than a leaning chimney?
What are the typical next steps?
- Treat the cracks as a hard flaunching that lacks flexibility.
- Ask a chimney contractor to renew the crown if it is to be repaired.
- Do not describe the stack as leaning because the new mortar has cracked.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
If the pots are still upright, can the flaunching be ignored?
No. Upright pots answer whether the stack looks plumb. They do not give the hard mix flexibility. The new sand-and-cement flaunching is already cracking. That crown is still the defect, even while the pots remain upright. Flexibility was what the hard mix did not give.
Does cracked flaunching mean the flue is blocked?
Not by itself. Cracks in the crown let rain into the top of the stack. They do not describe the flue. The survey has not tested the flue, and it has not said the hard mix has blocked anything inside the chimney.