Hi,

Very hypothetical questions for which there probably won't be definitive
answers, but that's OK, I'm doing an "expectations management" thing here:

"The bungalow" has a brick (both leaves) cavity external wall and all single
brick internals walls. The ground floor is poured concrete slab (not
beam/block). The building is 1950's in East Sussex, privately built (not
council stock). I don't have any reason to believe the house was built on a
structural raft.

Which of these statements is likely to be true:

a) The external walls sit on their own foundations, mechanically separate
from the floor slab;

b) The floor slab(s) pretty much sit on the dirt.

c) The internal non load bearing walls sit on the slab without foundations.

d) Internal centre load bearing wall has foundations and is separate from
the slab.

e) There is a DPC or some sort of water barrier in/under the slab.

-----

Answers or educated guesses would be most welcome.

I'm going to find out anyway, eventually, but I'd like to get some idea of
what to expect so I can plan things like "is it OK to build new brick walls
straight onto the slab" and "do I need to maintain an existing DPC" and "if
I dig out a section of floor slab right upto a wall, does the house fall
down" sort of things... :)

Many thanks,

Tim

Tim S wrote:
> Hi,
>
> Very hypothetical questions for which there probably won't be
> definitive answers, but that's OK, I'm doing an "expectations
> management" thing here:
>
> "The bungalow" has a brick (both leaves) cavity external wall and all
> single brick internals walls. The ground floor is poured concrete
> slab (not beam/block). The building is 1950's in East Sussex,
> privately built (not council stock). I don't have any reason to
> believe the house was built on a structural raft.

> Which of these statements is likely to be true:
>
> a) The external walls sit on their own foundations, mechanically
> separate from the floor slab;

Yes!

> b) The floor slab(s) pretty much sit on the dirt.

No! - They should sit on a hardcore base

> c) The internal non load bearing walls sit on the slab without
> foundations.

No! - They should sit on the concrete base.

> d) Internal centre load bearing wall has foundations and is separate
> from the slab.

No! - As above

> e) There is a DPC or some sort of water barrier in/under the slab.

Yes! - There should be some form of DPC, if not a polythene barrier, then 
possibly something like Bitumen or Synthaproof applied to the top of the 
concrete base and under the 2" floor screed.

>
> Answers or educated guesses would be most welcome.
>
> I'm going to find out anyway, eventually, but I'd like to get some
> idea of what to expect so I can plan things like "is it OK to build
> new brick walls straight onto the slab"

Yes!

 >and "do I need to maintain an existing DPC"

Yes! - Unless you are going to insert a new one.

>and "if I dig out a section of floor slab right upto a
> wall, does the house fall down" sort of things... :)

Very unlikely.


Tanner-'op

Hi, thanks for the detailed reply :)

Tanner-'op coughed up some electrons that declared:

> Tim S wrote:

<snip>

>> a) The external walls sit on their own foundations, mechanically
>> separate from the floor slab;
> 
> Yes!

Ah good. That's as I was hoping.
 
>> b) The floor slab(s) pretty much sit on the dirt.
> 
> No! - They should sit on a hardcore base

OK, silly me, of course hardcore is involved. But the hardcore sits on the
dirt? What I really meant was the floor slab is not likely to be hanging on
the foundations?

>> c) The internal non load bearing walls sit on the slab without
>> foundations.
> 
> No! - They should sit on the concrete base.

Sorry, I'm lost. Do you mean the concrete layer of the floor slab, not
including screed?

>> d) Internal centre load bearing wall has foundations and is separate
>> from the slab.
> 
> No! - As above

OK. 

>> e) There is a DPC or some sort of water barrier in/under the slab.
> 
> Yes! - There should be some form of DPC, if not a polythene barrier, then
> possibly something like Bitumen or Synthaproof applied to the top of the
> concrete base and under the 2" floor screed.

OK. It was the 1950's bit that caused me to question - I don't know what
they were doing back then. Sounds like judicious use of synthaproof would
be in order when replacing or repairing bits of the floor.

>>
>> Answers or educated guesses would be most welcome.
>>
>> I'm going to find out anyway, eventually, but I'd like to get some
>> idea of what to expect so I can plan things like "is it OK to build
>> new brick walls straight onto the slab"
> 
> Yes!

Splendid. Got 4 internal walls to build. Two will be brick because they will
form a new shower room and I hate drywall for shower/toilet rooms. The
brick walls are quit short and support very little apart from there own
weight so there's  probably not much to worry about.

BCO will soon complain if I'm doing something daft, but I'd rather not give
him the chance.

The other two will be wood stud drywall because there's no reason not to.

>  >and "do I need to maintain an existing DPC"
> 
> Yes! - Unless you are going to insert a new one.
> 
>>and "if I dig out a section of floor slab right upto a
>> wall, does the house fall down" sort of things... :)
> 
> Very unlikely.

Good. I didn't think it was very likely, but neither do I fancy causing
expensive damage or quick building a brick tomb for myself :)

Cheers

Tim

The message <48a7014e$0$625$5a6aecb4@news.aaisp.net.uk>
from Tim S  contains these words:

> "The bungalow" has a brick (both leaves) cavity external wall and all single
> brick internals walls. The ground floor is poured concrete slab (not
> beam/block). The building is 1950's in East Sussex, privately built (not
> council stock). I don't have any reason to believe the house was built on a
> structural raft.

> Which of these statements is likely to be true:

> a) The external walls sit on their own foundations, mechanically separate
> from the floor slab;

My parents had a house built in 1953 or 1954. I don't recall very much
about the construction (which is why I have made no attempt to answer
the other questions) but I am sure the foundations for the outside walls
were wide (perhaps 2 foot wide) and shallow. I don't think they were
much deeper than they were wide. I think the foundations were concrete
strip on a layer of brick rubble but I wouldn't like to swear to that.

Downstairs floors were concrete. There was still a wood shortage at the
time so suspended floors were at least uncommon and may well have been
banned. 

-- 
Roger Chapman

Roger coughed up some electrons that declared:

> The message <48a7014e$0$625$5a6aecb4@news.aaisp.net.uk>
> from Tim S  contains these words:
> 
>> "The bungalow" has a brick (both leaves) cavity external wall and all
>> single brick internals walls. The ground floor is poured concrete slab
>> (not beam/block). The building is 1950's in East Sussex, privately built
>> (not council stock). I don't have any reason to believe the house was
>> built on a structural raft.
> 
>> Which of these statements is likely to be true:
> 
>> a) The external walls sit on their own foundations, mechanically separate
>> from the floor slab;
> 
> My parents had a house built in 1953 or 1954. I don't recall very much
> about the construction (which is why I have made no attempt to answer
> the other questions) but I am sure the foundations for the outside walls
> were wide (perhaps 2 foot wide) and shallow. I don't think they were
> much deeper than they were wide. I think the foundations were concrete
> strip on a layer of brick rubble but I wouldn't like to swear to that.

Heh - probably end up with deeper foundations on the conservatory :)
 
> Downstairs floors were concrete. There was still a wood shortage at the
> time so suspended floors were at least uncommon and may well have been
> banned.
> 

That's interesting. I did wonder why suspended wood floors seemed rare after
the 30's.

Cheers

Tim

Tim S wrote:
> Hi,
> 
> Very hypothetical questions for which there probably won't be definitive
> answers, but that's OK, I'm doing an "expectations management" thing here:
> 
> "The bungalow" has a brick (both leaves) cavity external wall and all single
> brick internals walls. The ground floor is poured concrete slab (not
> beam/block). The building is 1950's in East Sussex, privately built (not
> council stock). I don't have any reason to believe the house was built on a
> structural raft.
> 
> Which of these statements is likely to be true:
> 
> a) The external walls sit on their own foundations, mechanically separate
> from the floor slab;
> 

sort of. Ther will be a damp stopper somewhere in the floor slab: this 
may be contigouus with the outside DPC in which case the walls and floor 
may actually be connected, or it mauy not.

> b) The floor slab(s) pretty much sit on the dirt.
> 
Yes.

> c) The internal non load bearing walls sit on the slab without foundations.
> 
Yes.

> d) Internal centre load bearing wall has foundations and is separate from
> the slab.
> 

One hopes so.

> e) There is a DPC or some sort of water barrier in/under the slab.
> 

One hopes so.

I am trying to remember standard practice..ISTR that in general te 
external DPC is lower than the internal one..so floors are normally 
above damp by some margin.

I suspect that the way they would have approached this sort of site 
build would have been to build strip foundations for the wall - probably 
not very deep - maybe not even on poured concrete, and build up to damp 
about 2-3 bricks above soil level.

Then in goes outer danp course, and a course higher, in goes inner damp.

Now at some stage the builder will shovel in his rubble and old cement 
crap and build up the interior to the inner damp level, possibly 
finshing with a  sand layer; if its was a modern slab he would then lay 
a plastic sheet over it, and cast his concrete on that or maybe caat 
concrete up to damp, then plastic sheet and screed over.

However in them days it MIGHT have been cast concrete and paint with 
bitumen paint..and not even screed over.

My parents' house built in 1953 and the ones built across the road from 
it should give me a clue, but memory is hazy..I remember walls with DPC 
in them allright, and the 'floor' being full of broken bricks, and all 
eventually concreted over, but I cant recall and damp proof membranes 
going down. Maybe they did use screed over plastic sheet even then.










> -----
> 
> Answers or educated guesses would be most welcome.
> 
> I'm going to find out anyway, eventually, but I'd like to get some idea of
> what to expect so I can plan things like "is it OK to build new brick walls
> straight onto the slab" and "do I need to maintain an existing DPC" and "if
> I dig out a section of floor slab right upto a wall, does the house fall
> down" sort of things... :)
> 
> Many thanks,
> 
> Tim

Tim S wrote:
> Roger coughed up some electrons that declared:
> 
>> The message <48a7014e$0$625$5a6aecb4@news.aaisp.net.uk>
>> from Tim S  contains these words:
>>
>>> "The bungalow" has a brick (both leaves) cavity external wall and all
>>> single brick internals walls. The ground floor is poured concrete slab
>>> (not beam/block). The building is 1950's in East Sussex, privately built
>>> (not council stock). I don't have any reason to believe the house was
>>> built on a structural raft.
>>> Which of these statements is likely to be true:
>>> a) The external walls sit on their own foundations, mechanically separate
>>> from the floor slab;
>> My parents had a house built in 1953 or 1954. I don't recall very much
>> about the construction (which is why I have made no attempt to answer
>> the other questions) but I am sure the foundations for the outside walls
>> were wide (perhaps 2 foot wide) and shallow. I don't think they were
>> much deeper than they were wide. I think the foundations were concrete
>> strip on a layer of brick rubble but I wouldn't like to swear to that.
> 
> Heh - probably end up with deeper foundations on the conservatory :)
>  
>> Downstairs floors were concrete. There was still a wood shortage at the
>> time so suspended floors were at least uncommon and may well have been
>> banned.
>>
> 
> That's interesting. I did wonder why suspended wood floors seemed rare after
> the 30's.
> 

Poured concrete was cheaper than wood, basically.

And it doesn't rot,

Its cold tho. But then came the 60's and FITTED CARPETS.


> Cheers
> 
> Tim

Tim S wrote:
> Hi, thanks for the detailed reply :)
>
> Tanner-'op coughed up some electrons that declared:
>
>> Tim S wrote:
>
> <snip>
>
>>> a) The external walls sit on their own foundations, mechanically
>>> separate from the floor slab;
>>
>> Yes!
>
> Ah good. That's as I was hoping.
>
>>> b) The floor slab(s) pretty much sit on the dirt.
>>
>> No! - They should sit on a hardcore base
>
> OK, silly me, of course hardcore is involved. But the hardcore sits
> on the dirt? What I really meant was the floor slab is not likely to
> be hanging on the foundations?

No - the slab will be independant of the wall foundations.

>>> c) The internal non load bearing walls sit on the slab without
>>> foundations.
>>
>> No! - They should sit on the concrete base.
>
> Sorry, I'm lost. Do you mean the concrete layer of the floor slab, not
> including screed?

The floor slab - Yes.  Discount the screed for *any* structural support as 
that is laid after the walls have been constructed,

Snipped

Tanner-'op

On 16 Aug,  
     "Tanner-'op" <tannerop@i......nvalid.com> wrote:

> Tim S wrote:
> > Hi,
> >
> > Very hypothetical questions for which there probably won't be
> > definitive answers, but that's OK, I'm doing an "expectations
> > management" thing here:
> >
> > "The bungalow" has a brick (both leaves) cavity external wall and all
> > single brick internals walls. The ground floor is poured concrete
> > slab (not beam/block). The building is 1950's in East Sussex,
> > privately built (not council stock). I don't have any reason to
> > believe the house was built on a structural raft.
> 
> > Which of these statements is likely to be true:
> >
> > a) The external walls sit on their own foundations, mechanically
> > separate from the floor slab;
> 
> Yes!
> 
> > b) The floor slab(s) pretty much sit on the dirt.
> 
> No! - They should sit on a hardcore base
> 
> > c) The internal non load bearing walls sit on the slab without
> > foundations.
> 
> No! - They should sit on the concrete base.
> 
> > d) Internal centre load bearing wall has foundations and is separate
> > from the slab.
> 
> No! - As above
> 
> > e) There is a DPC or some sort of water barrier in/under the slab.
> 
> Yes! - There should be some form of DPC, if not a polythene barrier, then 
> possibly something like Bitumen or Synthaproof applied to the top of the 
> concrete base and under the 2" floor screed.
> 
> >
> > Answers or educated guesses would be most welcome.
> >
> > I'm going to find out anyway, eventually, but I'd like to get some
> > idea of what to expect so I can plan things like "is it OK to build
> > new brick walls straight onto the slab"
> 
> Yes!
> 
>  >and "do I need to maintain an existing DPC"
> 
> Yes! - Unless you are going to insert a new one.
> 
> >and "if I dig out a section of floor slab right upto a
> > wall, does the house fall down" sort of things... :)
> 
> Very unlikely.
> 
> 
> Tanner-'op 

Comments more like 60s/70s or later construction. I wouldn't like to confirm
the same applied in the 50s.



-- 
  B Thumbs
  Change lycos to yahoo to reply

Tanner-'op coughed up some electrons that declared:

> Tim S wrote:

<snip>

>> OK, silly me, of course hardcore is involved. But the hardcore sits
>> on the dirt? What I really meant was the floor slab is not likely to
>> be hanging on the foundations?
> 
> No - the slab will be independant of the wall foundations.
> 

Thanks

>>>> c) The internal non load bearing walls sit on the slab without
>>>> foundations.
>>>
>>> No! - They should sit on the concrete base.
>>
>> Sorry, I'm lost. Do you mean the concrete layer of the floor slab, not
>> including screed?
> 
> The floor slab - Yes.  Discount the screed for *any* structural support as
> that is laid after the walls have been constructed,

Ah. So when I start digging, I might expect the bricks to be an inch or two
under the floor surface, depending on how much screed went down.

Again, thanks. This is very helpful.

Cheers

Tim

The Natural Philosopher coughed up some electrons that declared:

> Tim S wrote:

<snip>

> 
> sort of. Ther will be a damp stopper somewhere in the floor slab: this
> may be contigouus with the outside DPC in which case the walls and floor
> may actually be connected, or it mauy not.
> 
>> b) The floor slab(s) pretty much sit on the dirt.
>> 
> Yes.
>> c) The internal non load bearing walls sit on the slab without
>> foundations.
>> 
> Yes.
> 
>> d) Internal centre load bearing wall has foundations and is separate from
>> the slab.
>> 
> 
> One hopes so.
> 
>> e) There is a DPC or some sort of water barrier in/under the slab.
>> 
> 
> One hopes so.
> 

OK, concensus. All good to know.

> I am trying to remember standard practice..ISTR that in general te
> external DPC is lower than the internal one..so floors are normally
> above damp by some margin.
> 
> I suspect that the way they would have approached this sort of site
> build would have been to build strip foundations for the wall - probably
> not very deep - maybe not even on poured concrete, and build up to damp
> about 2-3 bricks above soil level.
> 
> Then in goes outer danp course, and a course higher, in goes inner damp.
> 
> Now at some stage the builder will shovel in his rubble and old cement
> crap and build up the interior to the inner damp level, possibly
> finshing with a  sand layer; if its was a modern slab he would then lay
> a plastic sheet over it, and cast his concrete on that or maybe caat
> concrete up to damp, then plastic sheet and screed over.

Ah, this *is* interesting. Hadn't considered there might be a difference
between inner and out DPC levels. 

> However in them days it MIGHT have been cast concrete and paint with
> bitumen paint..and not even screed over.

Right. Something else to look for. 

> My parents' house built in 1953 and the ones built across the road from
> it should give me a clue, but memory is hazy..I remember walls with DPC
> in them allright, and the 'floor' being full of broken bricks, and all
> eventually concreted over, but I cant recall and damp proof membranes
> going down. Maybe they did use screed over plastic sheet even then.
> 

If I get the lekky meter moved, that will be a good time for some
exploratory work as I need to dig a big hole next to the outside wall and
core drill through the floor and wall for some ducts (not big ducts,
probably a couple of 60-odd mm) for SWA cables to outside.

The "real" work revolves around converting the end of a small and useless
(for us, suited my parents just fine) room to a shower and loo. As it
happens, there's a natural nook that could house a 1x1m shower in such away
that a wet room would work without piddling water upto and over the loo and
out the door (one of the usual complaints about wetrooms). It would also be
the place for people doing gardening, hairy dogs and naked mud wrestling
women to oblute and/or clean up in, so a hoseable floor is a bonus.

So, need to slope the floor and install drainage. Might as well lift it and
relay with insulation and UFH it too. The area isn't that large so the
amount of work, rubble and concrete mixing isn't huge. But I was wondering
if there'd be any gotcha's. Probably not by the sound of it.

Many thanks indeed.

One day, there will be photos.

And my wife will buy you all a drink ;->

She thinks I'm planning to much. I keep pointing out all the near disasters
on Grand Designs...

Cheers

Tim

me9@privacy.net wrote:
> On 16 Aug,
>     "Tanner-'op" <tannerop@i......nvalid.com> wrote:
>
>> Tim S wrote:
>>> Hi,
>>>
>>> Very hypothetical questions for which there probably won't be
>>> definitive answers, but that's OK, I'm doing an "expectations
>>> management" thing here:
>>>
>>> "The bungalow" has a brick (both leaves) cavity external wall and
>>> all single brick internals walls. The ground floor is poured
>>> concrete slab (not beam/block). The building is 1950's in East
>>> Sussex, privately built (not council stock). I don't have any
>>> reason to believe the house was built on a structural raft.
>>
>>> Which of these statements is likely to be true:
>>>
>>> a) The external walls sit on their own foundations, mechanically
>>> separate from the floor slab;
>>
>> Yes!
>>
>>> b) The floor slab(s) pretty much sit on the dirt.
>>
>> No! - They should sit on a hardcore base
>>
>>> c) The internal non load bearing walls sit on the slab without
>>> foundations.
>>
>> No! - They should sit on the concrete base.
>>
>>> d) Internal centre load bearing wall has foundations and is separate
>>> from the slab.
>>
>> No! - As above
>>
>>> e) There is a DPC or some sort of water barrier in/under the slab.
>>
>> Yes! - There should be some form of DPC, if not a polythene barrier,
>> then possibly something like Bitumen or Synthaproof applied to the
>> top of the concrete base and under the 2" floor screed.
>>
>>>
>>> Answers or educated guesses would be most welcome.
>>>
>>> I'm going to find out anyway, eventually, but I'd like to get some
>>> idea of what to expect so I can plan things like "is it OK to build
>>> new brick walls straight onto the slab"
>>
>> Yes!
>>
>>  >and "do I need to maintain an existing DPC"
>>
>> Yes! - Unless you are going to insert a new one.
>>
>>> and "if I dig out a section of floor slab right upto a
>>> wall, does the house fall down" sort of things... :)
>>
>> Very unlikely.
>>
>>
>> Tanner-'op
>
> Comments more like 60s/70s or later construction. I wouldn't like to
> confirm the same applied in the 50s.

Did my apprenticeship in the mid 60's and I can remember the old college 
tutors giving us information on the types of foundations used in 'earlier 
times', and all of what I have had said would have been around in the 50's - 
with the construction methods developing rapidly to accomodate the 
prefabricated building boom of that time - and if I remember correctly, 
leading to the 'development' of the first set of 'National' Building 
Regulations around the mid to late 60's (prior that, the old local byelaws 
covered building control).

As a matter of interest, I have been involved in many repairs on local 
authority housing of that period and have seldom come across foundations and 
concrete bases laid directly onto the dirt - a bad practice due to 
chemical/sulphate reactions between the earth and concrete (a problem that 
also arose in the 60's and '70's when old colliery waste was used as a 
hardcore).

Tanner-'op