I moved in to a 1970’s detached house with suspended floor. There’s nearly 2 foot of space below the ground floor. I wanted to check the insulation under the floor and the ground appears to be ash from a fire.

Was it standard practice to have a fire before building the house?

Seems dry and mould free do that’s good.

Probably built on the embers of a ancient wickerman.

We have something similar, but just dirt rather than haunted ash.

You’ve seen Poltergeist, right?

Check it’s not red ash. If so, it’s a real problem.

Ashtroturf

Booom, perchy is back.

Dead people

1970’s build so highly unlikely to be red Ash.

Aye carumba, people just will not learn!

Has nobody seen Poltergeist? The Shining?

One last time: DO NOT BUY HOUSES BUILT ON CEMETERIES, INDIAN BURIAL GROUNDS, or in the OP’s case, MASS MURDER BODY-DISPOSAL FIREPITS.

We have the same- ours appears to be a money pit 😕

May have been a blinding of lean-mix concrete or PFA which has degraded to look like ash.

Or have you got a crematorium near you?

It’s built on the site of a burned down crematorium.

Now is the time to put a proper solum , a roll of 250 DPM and a lean mix concrete over the whole area 50mm maybe more at bits if it’s uneven
It will get rid of that musty smell and the wee beasties that are probably crawling over your face as you sleep

It’s the burnt dead Earth from the future.

My neighbor recently told me that the houses on our estate all have ash from power stations under the concrete floors. Don’t know if it’s the same or if it’s true but I don’t have any reason to doubt him as he was here when they were built. Ours is a bit older though, circa 1959

Ash from pulverised coal in power stations has a cementitous effect, maybe it’s instead of concrete. A construction site I worked on in the ’70s used granulated blast furnace slag as backfill; that might look like ash. Are you anywhere near a steelworks?

We’ve similar – a 60-70cm void under the front, down to 20cm at the back of the house. Our issue is that the central heating pipes all half block the access hatch – any work would involve moving them…

Floored some kind of sand/grit.

I’ve already had a boy crawl around down there to send TV aerial under the floor, it’s all accessible. I too am tempted to pop some insulation in.

Red ash is only a problem if it’s in direct contact with concrete isn’t it ?
The sulphates eat away at the concrete causing it to blow.
From your description you have a suspended (timber ?) floor with a 2 ft void under it , so it will never be in contact with it. So presumably no problem unless you bridge that gap somehow

Floor in our house is concrete but suspended. Will I die if I drill a hole to find out what’s down there?

Floor in our house is concrete but suspended. Will I die if I drill a hole to find out what’s down there?

You’ll put a hole through both the insulation and damp proof membrane so I wouldn’t. If it’s suspended you’ll have air bricks you can look through. They may be telescopic though in which case you’ll struggle without a boroscope. You can get them for under 100 quid though which is far cheaper than knacking your floor up.

Realistically though all you’re going to see is a 300 to 500mm void with a layer of roughly poured lean mix over it and a shit load of insects.

if you get a concussion you’ll probably see the plague victims that haunt it, maybe make a sitcom out of the situation?

You’d be amazed how much of the ground in urban areas is built up artificially, even if it doesn’t look like it. I investigate soils for a living to make sure they’re environmentally safe and ash fill is very common in brownfield sites from the early to mid twentieth century.

Ash from industry was readily available and cheap so was often used to alter levels and could well be what’s under your house. Ofteb it’s mixed with brick fragments but sometimes it’s just ash. It’s not done anymore because it contains loads of stuff that’s harmful for health.

We live in a house with a large vaulted cellar, seemingly predating the construction of the house itself. The floor is comprised of large York Stone flags, one of which has clearly been lifted and poorly replaced at some point in the past (>20 years as that’s how long we’ve been here).

Do I lift it to see what’s underneath, or leave well enough alone?

Thank you, there’s some helpful and scary answers.

Take care insulating under suspended timber floor. It’s great for stopping draughts and making the room feel warmer but without special attention to membranes and air flow you can end up with condensation that will rot your timbers and destroy your floor. There are companies who specialise in this or you can get advice from insulation suppliers.