I need to raise the floor level of an area about 2.5 by 1.5 metres which is
a covered area between the back door and the outside toilet and store which
have the same floor height as the kitchen

The base is slabs on hardcore which have been in place for 60+ years and are
flat and level

The area has been enclosed for years with wooden frames and doors and
windows which I have removed

The infill will be 125 mm total

My plan is 100mm concrete on top of dpm laid on the slabs

construct new frames from 75 x 50 studding on top of this and enclose

Finish with 25 mm of screed to get finished level

from what I have read the screeding wont be easy but it is only a small area
and dead flat is not necessary

I am looking at 4.5 sharp sand to 1 cement and a fairly dry mix ( it has
been some 25 years since I last did any screed so any tips appreciated)

Does this sound ok or should I reduce the concrete thickness and increase
the screed thickness?

Regards

TMC wrote:

I need to raise the floor level of an area about 2.5 by 1.5 metres which
is a covered area between the back door and the outside toilet and store
which have the same floor height as the kitchen

The base is slabs on hardcore which have been in place for 60+ years and
are flat and level

The area has been enclosed for years with wooden frames and doors and
windows which I have removed

The infill will be 125 mm total

My plan is 100mm concrete on top of dpm laid on the slabs

construct new frames from 75 x 50 studding on top of this and enclose

Finish with 25 mm of screed to get finished level

from what I have read the screeding wont be easy but it is only a small
area and dead flat is not necessary

I am looking at 4.5 sharp sand to 1 cement and a fairly dry mix ( it has
been some 25 years since I last did any screed so any tips appreciated)

Does this sound ok or should I reduce the concrete thickness and increase
the screed thickness?

Regards

Little bit thin for screed, though I have seen worse and you'd probbaly be
OK for such a small area - but is it subject to freezing?

An SBR modified screed is what I used when I needed only an inch thick -
that can go as low as 10mm if you follow all the process.

--
Tim Watts

"Tim Watts" wrote in message
...
TMC wrote:

I need to raise the floor level of an area about 2.5 by 1.5 metres which
is a covered area between the back door and the outside toilet and store
which have the same floor height as the kitchen

The base is slabs on hardcore which have been in place for 60+ years and
are flat and level

The area has been enclosed for years with wooden frames and doors and
windows which I have removed

The infill will be 125 mm total

My plan is 100mm concrete on top of dpm laid on the slabs

construct new frames from 75 x 50 studding on top of this and enclose

Finish with 25 mm of screed to get finished level

from what I have read the screeding wont be easy but it is only a small
area and dead flat is not necessary

I am looking at 4.5 sharp sand to 1 cement and a fairly dry mix ( it has
been some 25 years since I last did any screed so any tips appreciated)

Does this sound ok or should I reduce the concrete thickness and increase
the screed thickness?

Regards

Little bit thin for screed, though I have seen worse and you'd probbaly be
OK for such a small area - but is it subject to freezing?

An SBR modified screed is what I used when I needed only an inch thick -
that can go as low as 10mm if you follow all the process.

--
Tim Watts

not subject to freezing roof is 100mm concrete, stud walls will have 75mm
insulation

Will be at least frost protection heating to start with for outside toilet
and washing machine in the store area which will be open to the new enclosed
area

"TMC" wrote in message
...
I need to raise the floor level of an area about 2.5 by 1.5 metres which is
a covered area between the back door and the outside toilet and store which
have the same floor height as the kitchen

The base is slabs on hardcore which have been in place for 60+ years and
are flat and level

The area has been enclosed for years with wooden frames and doors and
windows which I have removed

The infill will be 125 mm total

My plan is 100mm concrete on top of dpm laid on the slabs

construct new frames from 75 x 50 studding on top of this and enclose

Finish with 25 mm of screed to get finished level

from what I have read the screeding wont be easy but it is only a small
area and dead flat is not necessary

I am looking at 4.5 sharp sand to 1 cement and a fairly dry mix ( it has
been some 25 years since I last did any screed so any tips appreciated)

Does this sound ok or should I reduce the concrete thickness and increase
the screed thickness?

will it be a heated internal space? if so consider sticking some sheet
insulation under your slab (also cut down on the materials and mixing)

Jim K

Jim K wrote:

"TMC" wrote in message
...
I need to raise the floor level of an area about 2.5 by 1.5 metres which
is a covered area between the back door and the outside toilet and store
which have the same floor height as the kitchen

The base is slabs on hardcore which have been in place for 60+ years and
are flat and level

The area has been enclosed for years with wooden frames and doors and
windows which I have removed

The infill will be 125 mm total

My plan is 100mm concrete on top of dpm laid on the slabs

construct new frames from 75 x 50 studding on top of this and enclose

Finish with 25 mm of screed to get finished level

from what I have read the screeding wont be easy but it is only a small
area and dead flat is not necessary

I am looking at 4.5 sharp sand to 1 cement and a fairly dry mix ( it has
been some 25 years since I last did any screed so any tips appreciated)

Does this sound ok or should I reduce the concrete thickness and increase
the screed thickness?

will it be a heated internal space? if so consider sticking some sheet
insulation under your slab (also cut down on the materials and mixing)

Jim K

Just a thought then: If the base is stable, what about a thin layer of
builder's sand, DPM, celotex (or equiv) and an extra thick reinforced top
screed and forget the concrete entirely?

The sand protects the DPM and allows the celotex to bed nicely. "Reinforced"
means either fibre additive or a bit of light wire mesh (4mm or more wire
size) and use 75mm screed thickness. Sounds like 50mm celotex based on the
earlier numbers...

Less material overall as Jim says, and a less cold floor and a 1-mixing
stage laying operation rather than 2.

--
Tim Watts

"Tim Watts" wrote in message
...
Jim K wrote:

"TMC" wrote in message
...
I need to raise the floor level of an area about 2.5 by 1.5 metres which
is a covered area between the back door and the outside toilet and store
which have the same floor height as the kitchen

The base is slabs on hardcore which have been in place for 60+ years and
are flat and level

The area has been enclosed for years with wooden frames and doors and
windows which I have removed

The infill will be 125 mm total

My plan is 100mm concrete on top of dpm laid on the slabs

construct new frames from 75 x 50 studding on top of this and enclose

Finish with 25 mm of screed to get finished level

from what I have read the screeding wont be easy but it is only a small
area and dead flat is not necessary

I am looking at 4.5 sharp sand to 1 cement and a fairly dry mix ( it has
been some 25 years since I last did any screed so any tips appreciated)

Does this sound ok or should I reduce the concrete thickness and
increase
the screed thickness?

will it be a heated internal space? if so consider sticking some sheet
insulation under your slab (also cut down on the materials and mixing)

Jim K

Just a thought then: If the base is stable, what about a thin layer of
builder's sand, DPM, celotex (or equiv) and an extra thick reinforced top
screed and forget the concrete entirely?

The sand protects the DPM and allows the celotex to bed nicely.
"Reinforced"
means either fibre additive or a bit of light wire mesh (4mm or more wire
size) and use 75mm screed thickness. Sounds like 50mm celotex based on the
earlier numbers...

Less material overall as Jim says, and a less cold floor and a 1-mixing
stage laying operation rather than 2.

--
Tim Watts


Has merit

I had considered the celotex approach with concrete sub base and then screed
but the layers were getting too thin

would it be worth putting in say 25mm of celotex then 60mm concrete 40 mm
screed? or would the concrete layer be too thin to use before the screed is
added

Also I was looking at the subfloor and enclose method to allow me to close
the area before laying the final floor inside

There are foxes cats and children (not normally at the same time) who could
leave impressions on the floor if it is not enclosed

I suppose I could run a course of blues both sides first to mount the frames
on but that would take time as well

Also I already have the concrete ballast as it was part of a larger load for
the shed bases and drive construction

Regards



(this area provides the access to the rear garden)

"TMC" wrote in message
...

"Tim Watts" wrote in message
...
Jim K wrote:

"TMC" wrote in message
...
I need to raise the floor level of an area about 2.5 by 1.5 metres which
is a covered area between the back door and the outside toilet and store
which have the same floor height as the kitchen

The base is slabs on hardcore which have been in place for 60+ years
and
are flat and level

The area has been enclosed for years with wooden frames and doors and
windows which I have removed

The infill will be 125 mm total

My plan is 100mm concrete on top of dpm laid on the slabs

construct new frames from 75 x 50 studding on top of this and enclose

Finish with 25 mm of screed to get finished level

from what I have read the screeding wont be easy but it is only a small
area and dead flat is not necessary

I am looking at 4.5 sharp sand to 1 cement and a fairly dry mix ( it
has
been some 25 years since I last did any screed so any tips appreciated)

Does this sound ok or should I reduce the concrete thickness and
increase
the screed thickness?

will it be a heated internal space? if so consider sticking some sheet
insulation under your slab (also cut down on the materials and mixing)

Jim K

Just a thought then: If the base is stable, what about a thin layer of
builder's sand, DPM, celotex (or equiv) and an extra thick reinforced top
screed and forget the concrete entirely?

The sand protects the DPM and allows the celotex to bed nicely.
"Reinforced"
means either fibre additive or a bit of light wire mesh (4mm or more wire
size) and use 75mm screed thickness. Sounds like 50mm celotex based on
the
earlier numbers...

Less material overall as Jim says, and a less cold floor and a 1-mixing
stage laying operation rather than 2.

--
Tim Watts


Has merit

I had considered the celotex approach with concrete sub base and then
screed but the layers were getting too thin

would it be worth putting in say 25mm of celotex then 60mm concrete 40 mm
screed? or would the concrete layer be too thin to use before the screed
is added

I'd forget the screed altogether and just trowel off the concrete (with
Tim's reinforcement idea) over say? 50mm celotex.- one hit job done

Also I was looking at the subfloor and enclose method to allow me to close
the area before laying the final floor inside

There are foxes cats and children (not normally at the same time) who
could leave impressions on the floor if it is not enclosed

If a major issue?? bit of filler later? won't it have a floor covering
eventually? you could guard it whilst the top cures ;)

Jim K

TMC wrote:


Has merit

I had considered the celotex approach with concrete sub base and then
screed but the layers were getting too thin

would it be worth putting in say 25mm of celotex then 60mm concrete 40 mm
screed? or would the concrete layer be too thin to use before the screed
is added

Also I was looking at the subfloor and enclose method to allow me to close
the area before laying the final floor inside

There are foxes cats and children (not normally at the same time) who
could leave impressions on the floor if it is not enclosed

I suppose I could run a course of blues both sides first to mount the
frames on but that would take time as well

Also I already have the concrete ballast as it was part of a larger load
for the shed bases and drive construction

Regards



(this area provides the access to the rear garden)

I don't see what the concrete+screed combo is buying here as it is causing a
compromise of thickness on both layers...

Concrete is normally used, by my understanding, as it goes down easily in
volume, is easy to move around until "about right" and sets strong - but in
large areas, is hard to get a good flat fine finish. Hence the screed -
though because I'm unpractised with dry screeding I actually find concrete
easier to work with - hence:

There's nothing to stop you being unconvential and laying 3-4" of concrete
on top of the insulation and dispense with the screed - use a fine aggregate
(5-10mm) and no lumpy 20mm stuff. Put some mesh in and make the top the
finished surface. If you desire an absolutely prefect finish, finish with
5mm or so self levelling compound (proper stuff like F Ball Stopgap 300, not
crap from B&Q - 1x 25kg bag ought to do it based on the area)

For small areas it's not hard to get concrete dead flat and nicely finished
if you have some formwork or guide rails around the edge and don't make the
concrete too wet. Once it is tamped and levelled, a quick polish with a
metal trowel (plasterers type, rectangular) will finish the surface - but
don't overdo this.

Cheers,

Tim

--
Tim Watts

"Tim Watts" wrote in message
...
TMC wrote:


Has merit

I had considered the celotex approach with concrete sub base and then
screed but the layers were getting too thin

would it be worth putting in say 25mm of celotex then 60mm concrete 40 mm
screed? or would the concrete layer be too thin to use before the screed
is added

Also I was looking at the subfloor and enclose method to allow me to
close
the area before laying the final floor inside

There are foxes cats and children (not normally at the same time) who
could leave impressions on the floor if it is not enclosed

I suppose I could run a course of blues both sides first to mount the
frames on but that would take time as well

Also I already have the concrete ballast as it was part of a larger load
for the shed bases and drive construction

Regards



(this area provides the access to the rear garden)

I don't see what the concrete+screed combo is buying here as it is causing
a
compromise of thickness on both layers...

Concrete is normally used, by my understanding, as it goes down easily in
volume, is easy to move around until "about right" and sets strong - but
in
large areas, is hard to get a good flat fine finish. Hence the screed -
though because I'm unpractised with dry screeding I actually find concrete
easier to work with - hence:

There's nothing to stop you being unconvential and laying 3-4" of concrete
on top of the insulation and dispense with the screed - use a fine
aggregate
(5-10mm) and no lumpy 20mm stuff. Put some mesh in and make the top the
finished surface. If you desire an absolutely prefect finish, finish with
5mm or so self levelling compound (proper stuff like F Ball Stopgap 300,
not
crap from B&Q - 1x 25kg bag ought to do it based on the area)

For small areas it's not hard to get concrete dead flat and nicely
finished
if you have some formwork or guide rails around the edge and don't make
the
concrete too wet. Once it is tamped and levelled, a quick polish with a
metal trowel (plasterers type, rectangular) will finish the surface - but
don't overdo this.

Cheers,

Tim

--
Tim Watts

sounds like a good plan as have already done 2 shed bases and the surface
was pretty smooth after a bit of gentle tamping

50mm cellotex ( I presume you mean the polystyrene sheet stuff rather than
branded cellotex) will reduce mixing by about 40% aside from the other
benefits

Thanks for the advice from all who contributed

Regards

"TMC" wrote in message
...

"Tim Watts" wrote in message
...
TMC wrote:


Has merit

I had considered the celotex approach with concrete sub base and then
screed but the layers were getting too thin

would it be worth putting in say 25mm of celotex then 60mm concrete 40
mm
screed? or would the concrete layer be too thin to use before the
screed
is added

Also I was looking at the subfloor and enclose method to allow me to
close
the area before laying the final floor inside

There are foxes cats and children (not normally at the same time) who
could leave impressions on the floor if it is not enclosed

I suppose I could run a course of blues both sides first to mount the
frames on but that would take time as well

Also I already have the concrete ballast as it was part of a larger load
for the shed bases and drive construction

Regards



(this area provides the access to the rear garden)

I don't see what the concrete+screed combo is buying here as it is
causing a
compromise of thickness on both layers...

Concrete is normally used, by my understanding, as it goes down easily in
volume, is easy to move around until "about right" and sets strong - but
in
large areas, is hard to get a good flat fine finish. Hence the screed -
though because I'm unpractised with dry screeding I actually find
concrete
easier to work with - hence:

There's nothing to stop you being unconvential and laying 3-4" of
concrete
on top of the insulation and dispense with the screed - use a fine
aggregate
(5-10mm) and no lumpy 20mm stuff. Put some mesh in and make the top the
finished surface. If you desire an absolutely prefect finish, finish with
5mm or so self levelling compound (proper stuff like F Ball Stopgap 300,
not
crap from B&Q - 1x 25kg bag ought to do it based on the area)

For small areas it's not hard to get concrete dead flat and nicely
finished
if you have some formwork or guide rails around the edge and don't make
the
concrete too wet. Once it is tamped and levelled, a quick polish with a
metal trowel (plasterers type, rectangular) will finish the surface - but
don't overdo this.

Cheers,

Tim

--
Tim Watts

sounds like a good plan as have already done 2 shed bases and the surface
was pretty smooth after a bit of gentle tamping

50mm cellotex ( I presume you mean the polystyrene sheet stuff rather than
branded cellotex) will reduce mixing by about 40% aside from the other
benefits

Thanks for the advice from all who contributed

Tim's plan also sounds good to me. I did a similar job years ago at our
first house when building a simple wooden conservatory/lean to greenhouse.
DPC and concrete straight onto an old patio (with a blinding of sand first)
topped of with some self levelling compound survived without blemish for the
six years we lived there.

Mike