Our fence went on fire!

[FedUpWithBriiiiick]

Our fence went on fire yesterday - not huge flames but the bottom's burnt away and there is damage to about one foot up.

No evidence of ignition, we back onto unclaimed land, no damage on other side of fence (or neighbours thankfully!)

Only reason we can think is that there was mulch next to the fence. It hasn't been overly hot here (NI) but dry for about a week (plants have been watered though so not tinder dry!). Was it a build up of heat from the compost underneath?

We have lifted all the mulch off now, and it has rained heavily overnight but still concerned about a possible reoccurrence!

Grateful for experience and knowledge!

What was the mulch? How thick?

People do find ash in the middle of layers of grass cuttings in their compost heaps.

Had you recently repainted the fence? Could fumes have helped the ignition?

Not a huge amount I don't think? Maybe 1/2" to 1" thick?

It was the bark chipping type.

The fence was painted over one month ago.

MILs fence caught on fire. It was from a chinese lantern blown there from somewhere else.

Any glass nearby reflecting sunlight onto it?

Compost sounds like a reasonable answer, but I'd have thought it needed to be much hotter before compost would ignite - remember our boiling summer two years ago? There were spontaneous garden fires then. Not this year...

It's probably best to move the mulch/compost to a separate fireproof container, though.

A very thick layer of unrotted green mulch might combust - e.g. grass clippings, but not an inch of bark.

Could be! Honestly it could just have been a random series of events that lead to the ignition. Not sure we'll ever get to the bottom of it...

One things for sure that area will be kept pretty watered from now on and stones are going down 😳

Agreed, it's not that hot here!

The mulch has been removed now anyway.

The area is for our new Japanese maple and nothing else is going in this year, so we will put stones down instead. Let's hope they aren't flammable 🤣

Thanks everyone - we will have to mark it up to bad luck and take more precautions going forward 👍

It's not the bark chips. Even fresh out of the chipper a layer that thin would barely get warm.

I wouldn't have thought that would ignite. Heat generated is proportional to volume, heat is lost proportionally to surface area. A 1 inch thick layer has a small volume and a huge surface area - it would lose heat quicker than it's gaining it.

The ignition isn't from the heat from the sun, it's from bacterial action. It's greater when the compost is moist - hence the importance of drying hay thoroughly before stacking it..

We had a large pile of green woodchippings in our garden at one point from a tree that was felled in full leaf. The heat that it generated was astonishing. I suspect its this combined with potentially flammable wood preservative on the fence.

Edited - Although sorry Ive just seen it was only an inch or so thick so perhaps not.

@FedUpWithBriiiiick Does anyone in your home smoke? Sounds rather like a discarded cigarette butt fire to me.

No smokers, and all the land behind the fence is overgrown and empty.

Neighbours are not smokers either.