The long put off ground floors insulation/underfloor heating is heading
for decision time.
One not entirely unexpected problem is what to do about a 9" brick, 2
storey, end wall which has quietly subsided by about 10mm over the last
60 or so years. An inspection dig found no exterior corbelling and the
wall standing on what appeared to be coarse gravel at 18" below soil
Building Control will be inspecting the flooring job and very unlikely
to miss spotting inadequate foundations. Involving insurers will wreck
the planned start of next Spring and may poison any future sales.
My current thinking is to involve a structural engineer and get any
advised *reinforcement* done as part of the main project. Or...?
Pardon the pun but this really is a rock and a hard place situation.
Given that you are aware that subsidence has taken place you may be
legally obliged to notify your insurers anyway because it something that
may significantly alter the degree of risk they have to bear. Likewise
if you come to sell and are asked if there has been any subsidence then
you might be liable to significant costs if you did not disclose it.
If the BCO insists on remedial action then your insurer will probably
pick up the bill and are likely to have to pay a large excess.
Not a nice situation to be in but you did ask.
The question is, is it actually subsidence or is is settlement?
Our house has a very slight slope towards the front, while our extension
has one to the rear. There were cracks at the join, but I was not not
bothered, as they weren't changing. When I moved the mortgage, the
valuer got worried about them and I had to call in a Structural Engineer
- he quickly confirmed that all the movement was settlement when the
house (and later the extension) were new and there was no ongoing
movement (mainly by asking me if there had been any changes over the
years) and therefore no problem.
Well... one might call it movement independent of the adjoining
structure. The bulk of the original house walls were studwork on 9"
dwarf walls clad with feather edge. Around 1938, the feather edge was
replaced with cement render on expanded metal. In 1995 we added some
external insulation and more render/feather edge so the entire house has
got heavier without any improvements to the foundations.
There has been about 2 mm movement since 1995. Whether this is ongoing
is beyond my knowledge.
Oh. I guess the criticism might be that it is moving in relation to the
rest of the house.
Not that fit Phil!
I do have a friend who digs holes for a living so not necessarily hugely
expensive. Own mix concrete barrowed in. Arisings disposed on the farm.
Done as part of the floor project so no extra making good.
Elsewhere where we have done this under agricultural barns of a similar
vintage, the holes were 1m x 1m x 750mm and probably only 10 days
between adjoining holes
Employing my expert long range x-ray goggles I can clearly see that your
problem is simple settlement rather than a potentially more legally
complicated subsidence situation.
If you (optionally) decide to deepen your founds when you make good your
floor I see no need to over describe your works to include scary,
insurance unfriendly, terms.
Your situation would be a lot simpler if your settlement issues were
resolved and the ground suitably aged before the local BCO became
I'm sure that small scale groundworks are common close to buildings in
an agricultural situation.
[Default] On Sat, 7 Dec 2013 19:35:22 +0000, a certain chimpanzee, Tim
You're not required to carry out remedial work (such as underpinning)
as part of any other alterations, so long as you don't make the
building worse than before, but if you do any underpinning, that has
Any renovation of a thermal element (i.e., insulating a floor) only
has to comply with the energy efficiency requirements and, as above,
not making the building any worse than before (e.g., reinstating a
damp-proof membrane if there was one before).
"If no-one on the internet wants a piece of this,
What are the issues if excavation for underpinning finds water? During
foundation trench work elsewhere, water was found at 1m!
The location is a river valley so we may have hit an ancient river
I hope to lower the floor by 100mm in this particular area. With screed
thick enough for under floor heating pipes, insulation, concrete
oversite, dpm and hard-core, I may be close to undermining the wall! The
alternative is to retain the existing step between rooms.
Elsewhere and probably here, the walls have a slate damp course. This
end of the house was once used as a dairy with through access for horse
and cart. Later construction has replaced the openings with patio doors
and a window.
[Default] On Sun, 8 Dec 2013 09:41:04 +0000, a certain chimpanzee, Tim
It sounds like you have something more complicated than simple
settlement. A reputable engineer's opinion is called for. It's
possible that the movement is caused by the ground under the
foundations being washed away.
If you go below the original foundations, even for the hardcore, then
it would be regarded as undermining the foundations, and may require
underpinning. You may get away with buttressing the existing
foundations (but given the information in the first paragraph,
doubtful), but this is something you don't want to start without
getting Building Control involved with at the earliest possible
"If no-one on the internet wants a piece of this,
Quite likely in my parents day as an unguttered shed roof discharged on
to a concrete path abutting this wall. One of my first moves after
purchasing the freehold was to lower the soil levels below dpc and
remove the concrete paths. Sorted the damp and may have slowed the
movement. There are no soaks within 5m but this is a sloping site within
the river flood risk area so who knows what is happening down below.
The budget for an aided d-i-y job is below £3k so best to get it done, I
I will consult an engineer who knows the site.
The normal practice is to cement strips of glass over the joint/cracks
If they break the building is still moving, if not, don't worry.
Mark a date in the cement and take pix every few months for evidence.
Not likely to be moving on gravel.
You can underpin yourself as someone else has said.
Quite cheap to do if a lot of hard work. Only the cost of concrete.
ask your BCO for advice ... he will probably be best placed to provide
A structural Engineer is probably not going to do anything (unless
perhaps via over design) without a detailed survey into ground bearing -
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