Previously unknown basement rears it's ugly head

[kandgmitchell]

We own a flat in the north-west in which our daughter lives. It's in an old red brick school built in the early 1900's and converted to flats about 25 years ago.

 

Late last year a ground floor flat owner replaced some flooring and discovered a crack in the concrete which upon further investigation turned out to be a suspended slab over a basement no-one knew about. The developer had removed most of the external access stairs, levelled the ground and put a manhole cover over them. Roll on 25 years and when access is finally gained it is found the steel beams supporting the concrete slab have seriously corroded. So bad that emergency propping was required and the flat owner advised to move out. It appears the basement is entirely under that one flat.

 

This has now blighted the whole building. Two sales have fallen through and no-one is able to move or re-mortgage. The managing agents bailed out as they felt the building was "too much of a risk". The insurers have wiped their hands of it saying it's a maintenance issue. That has been disputed with the ombudsman since the situation was hidden and no maintenance could therefore take place. A decision is awaited.

 

The developer who was also the head landlord has gone into administration. That leaves us 25 leaseholders on the hook for repairs. I haven't been into the basement as yet but my first thought was to cut the beams out, drop the old concrete floor into the basement and then mass fill it with say foamed concrete topped with a slab. However, that suggestion has been poo pooed by the flat owner involved as they say they have been advised by surveyors and engineers not to do this as it would create "maintenance problems" (?) and cause damp in the affected flat, indeed no professional would be associated with any such proposal apparently.........

 

As yet we await a formal suggestion as to how to deal with this but to be honest it has to be cost effective because we will all have to pay and some leaseholders are just young couples in their first home and we haven't got loads of spare cash lying about.

 

Am I barking up the wrong tree with my idea (the volume is probably 4.5m x 5m x 3m) or are we looking at replacement steel beams with say block and beam and screed which involves much more labour?

[Nickfromwales]

56 minutes ago, kandgmitchell said:

We own a flat in the north-west in which our daughter lives. It's in an old red brick school built in the early 1900's and converted to flats about 25 years ago.

 

Late last year a ground floor flat owner replaced some flooring and discovered a crack in the concrete which upon further investigation turned out to be a suspended slab over a basement no-one knew about. The developer had removed most of the external access stairs, levelled the ground and put a manhole cover over them. Roll on 25 years and when access is finally gained it is found the steel beams supporting the concrete slab have seriously corroded. So bad that emergency propping was required and the flat owner advised to move out. It appears the basement is entirely under that one flat.

 

This has now blighted the whole building. Two sales have fallen through and no-one is able to move or re-mortgage. The managing agents bailed out as they felt the building was "too much of a risk". The insurers have wiped their hands of it saying it's a maintenance issue. That has been disputed with the ombudsman since the situation was hidden and no maintenance could therefore take place. A decision is awaited.

 

The developer who was also the head landlord has gone into administration. That leaves us 25 leaseholders on the hook for repairs. I haven't been into the basement as yet but my first thought was to cut the beams out, drop the old concrete floor into the basement and then mass fill it with say foamed concrete topped with a slab. However, that suggestion has been poo pooed by the flat owner involved as they say they have been advised by surveyors and engineers not to do this as it would create "maintenance problems" (?) and cause damp in the affected flat, indeed no professional would be associated with any such proposal apparently.........

 

As yet we await a formal suggestion as to how to deal with this but to be honest it has to be cost effective because we will all have to pay and some leaseholders are just young couples in their first home and we haven't got loads of spare cash lying about.

 

Am I barking up the wrong tree with my idea (the volume is probably 4.5m x 5m x 3m) or are we looking at replacement steel beams with say block and beam and screed which involves much more labour?

Does this affect the structural integrity of the building as a whole, or is it entirely isolated to this one ‘flat’?

[Russell griffiths]

I like your idea, pumped in from outside, leave it 300 mm below the floor level then break out the floor and remove then insulation and a concrete slab on top. 

[saveasteading]

I don't like the idea. An SE is the best bet.

 

The steel has to be examined. Rust isn't always as bad as first impressions.

But there are usually other options such as multiple small beams, additional supports or a wall underneath.

 

It's going to be expensive. Some insurers reject on any excuse. All you can do when getting a quote is answer to the best of your knowledge, so reread what you told them then try again.

 

You are all in this together. Have neighbours been below? Pictures would help.

 

[Nickfromwales]

It would all need to be excavated out, prove and prep the sub-base, then lay a major reinforced fundamental slab. Then build up off that.
 

Settlement of new works will be the crux, so this will need to be done a-la adding a new basement methinks (hard packing etc).

 

Will need a contractor with experience, and very good commercial insurance. 
 

Look into collateral warranties also, as a doomsday parachute, in case the contractor falls over mid / post project.