Loud banging noise - coming from kitchen - need help

[SuzieA]

We have an issue we need help with .
Loud banging in the kitchen, a very large bang (makes you jump), sounds like coming from under floor. Corner of kitchen near sink and where boiler is located.
There’s no consistency in timing on the bangs. It can happen one day every 30 minutes and then the next day intermittently.

There’s usually nothing happening when the bangs go off i.e. toilet being flushed, water on, washing machine one, heating on etc my parent are usually just sitting in the front room.



What we’ve done:

• Electrics checked no issues, sign of any damage and the lights are not affected by the bangs
• Plumbing – checked and had a shock arrestor installed to cold main pipe and a new stopcock (thought water hammer) but this has not resolved it
• Boiler – this has been checked and British gas reckons boiler is all good
• Sewer – checked the manhole outside of kitchen by back door and its clear, EVEN THOUGH you can really hear the sound from the drain with the cover up. Thames Water advise there have been no other issues logged of this nature in the area and no blockages either.

What else could it be, could it be coming back into the house from the sewer as we can really hear the bang outside when the drain cover is raised.

I have no idea on how to further diagnose this to resolve. Noise is making parents ill.

 

[Notch7]

Is it a solid floor or a suspended floor?

Does the foul drain go under the floor? Is it just your drain or shared.

Is it definitely the floor…..some people get load banging from GRP flat roofs for example.


Have you checked the hot and cold feeds to taps etc. maybe a hot pipe is expanding or contracting but is constrained by a tight clip or hitting a joist then suddenly releasing causing a bang.

 

[SuzieA]

Hey a suspended floor I believe , old house with large foundations
I’d need to confirm waste/foul but the stack is directly outside on back wall so without checking I think waste runs direct from outlet to this without really running under floor, but would need to check.
Drain looks like a typical shared drain as it will run from the terraced houses.

All hot and cold feeds seems to located near back wall of property, do you suggest we need to lift the kitchen floor to check these joists?
Only because we get the banging happening when absolutely nothing is running or happening in the house I,,e middle of night…., we’ve considered this

 

[Burnerman]

Has the property ever had the tendency to flood?
Drainage flap valves may be fitted, if so - they can also help with rat movements.
They don't bang though, but I have heard them 'clack'.
John

 

[SuzieA]

Hello, thanks for responding
Hi no tendency to flood, but end of garden backs onto a railway embankment so there are plenty of rats!
How would we check if they have been fitted?