Filling in a hole (former lightwell)

[Deluks]

I have been asked to fill a hole. It's a former coal chute or lightwell in a victorian property. The owner moved in about 20 years ago when it was a window, but she had window removed and filled in with breeze and rendered on the outside, The render only covers where the window was, there is exposed brick on the rest of it which is all blown and in need of a repoint.

It's about 4ft deep, and the opening is about 18" by about 30-36" with a removable heavy cast iron grate on top.
The hole is damp and lined with leaves and crap, there is dampness on the internal cellar wall, but the cellar is generally damp anyway.

What's the best way to lose this hole? Fill it in with earth, gravel, hardcore, combination of all the above? Any membranes or painting required?

I can just about get in there to work.

 

[noseall]

fill with mot to within 150mm of dpc, compact in stages, lay down dpm, then concrete.

 

[Deluks]

Thanks for the reply. now I need to know why, inquisitive type that I am

Why use a dpm outside? I'm not sure there is a DPC in this property, and no sign of any drilled holes. Is it worth treating, rendering the exposed underground brick before filling in?

The hole is outside, the bricked up opening being flush with the main house wall, which sits directly above it. The lightwell itself is formed by a brick surround, which hold back the rest of the garden. You seem to be describing a concrete 'cap' atop the hole, the rest of the ground around it is earth, planted shrubs suchlike, could the concrete be subsurface, with earty on top? I wish I'd taken a pic now.

 

[Nige F]

ask Bernard Cribbins ...."there was I, diggin` this hole"......."hole in the ground......."

 

[Deluks]

i imagined the coal chute to be attached to the building, hence the dpm.

Well I'm not sure that it was a coal chute that was converted to a window, or has always been a window. In any case it's a hole in the ground flush with the front of the house, 1 of the 4 brick walls which form this hole is the foundation wall of the house. The rest are retaining the front garden to a depth of 4ft.

The current plan.
My dad, a plasterer, suggested rendering the rest of the tatty brickwork below ground level, using a decent waterproofer in the mix to protect the wall from further damage. (I'd get him to do it but his portly, ale inspired figure would preclude this)

Come back next day, fill with mot, few inches of conc on top to level off. Assuming there is a dpc, this would be above ground level anyway so no need to worry about the concrete in contact with wall.

What befuddles me is what happens to rainwater around and below foundations, will this brick lined mot filled hole retain water, and if so what negative effects could this bring on?

 

[noseall]

rainwater around and below buildings are kept at bay by the dpm, and dpc and the presence of a cavity.

rainwater can be a problem in a clay substrate. but only when it dries out.

you cannot compress water. so any water that is completely trapped under a building will actually be fairly solid. however, if it is allowed to dry out then a building can suffer.

similarly, a building that has been built in clay ground with the presence of water sapping root systems i.e. trees or hedgerows close by and if these were later removed, then 'clay heave' can result.

heave occurs when water is allowed to return to parched clay (sucked dry by the roots) causing it to swell and actually lift floor slabs or even foundations.