I've recently built a new workshop in the garden, 5m square. It has a concrete
floor that sits on plastic sheet to stop the damp rising. The walls are timber
framed and clad with shiplap that has been treated externally. There is a
double glazed french window and a double glazed single door. The roof is
canted with an eight inch drop front to back. The whole structure is silicone
sealed and weatherproofed. The roof itself is of corrugated Coroline sheet
with a centre section that is semi opaque plastic sheet. Good enough to let
light in but not completely clear. Condensation is building up badly on the
plastic panels with a small amount on the Coroline. As yet the walls are not
insulated or lined and the floor not yet fitted. The walls are to be clad with
150mm rockwool and the floor with Kingspan blocks with 9mm Sterling board wall
panelling and 13mm T & G chipboard. The concrete was poured the second week in
January so has been down about seven weeks. I intend to insulate and board the
ceiling sections that are of Coroline with a centre section of clear 6mm
sandwich type of plastic panel. Problem is the condensation. Is there a likely
cure or will things improve when the walls and non-centre parts of the ceiling
are insulated. I don't want to do the ceiling insulation if the condensation
is to persist. Does anyone have an answer? Is the concrete cured? How long
does that take? Will the floor benefit from painting before I fit the bearers
and insulation?

--
for full context, visit https://www.homeownershub.com/uk-diy...p-1193640-.htm

On Monday, 27 February 2017 21:14:04 UTC, John Irving wrote:
I've recently built a new workshop in the garden, 5m square. It has a concrete
floor that sits on plastic sheet to stop the damp rising. The walls are timber
framed and clad with shiplap that has been treated externally. There is a
double glazed french window and a double glazed single door. The roof is
canted with an eight inch drop front to back. The whole structure is silicone
sealed and weatherproofed. The roof itself is of corrugated Coroline sheet
with a centre section that is semi opaque plastic sheet. Good enough to let
light in but not completely clear. Condensation is building up badly on the
plastic panels with a small amount on the Coroline. As yet the walls are not
insulated or lined and the floor not yet fitted. The walls are to be clad with
150mm rockwool and the floor with Kingspan blocks with 9mm Sterling board wall
panelling and 13mm T & G chipboard. The concrete was poured the second week in
January so has been down about seven weeks. I intend to insulate and board the
ceiling sections that are of Coroline with a centre section of clear 6mm
sandwich type of plastic panel. Problem is the condensation. Is there a likely
cure or will things improve when the walls and non-centre parts of the ceiling
are insulated. I don't want to do the ceiling insulation if the condensation
is to persist. Does anyone have an answer? Is the concrete cured? How long
does that take? Will the floor benefit from painting before I fit the bearers
and insulation?

Concrete takes about a month to cure, and of course contains a whole lot of water that evaporates slowly.

I don't see a point painting the concrete, if as you said you already have a dpm. If there is no dpm then a waterproof finish can help a lot. But it's still drying out.


NT

On 27/02/2017 21:14, John Irving wrote:
I've recently built a new workshop in the garden, 5m square. It has a
concrete

[snip]

January so has been down about seven weeks. I intend to insulate and
board the ceiling sections that are of Coroline with a centre section of clear 6mm
sandwich type of plastic panel. Problem is the condensation. Is there a
likely cure or will things improve when the walls and non-centre parts of the
ceiling are insulated. I don't want to do the ceiling insulation if the
condensation is to persist. Does anyone have an answer? Is the concrete cured? How long
does that take? Will the floor benefit from painting before I fit the
bearers and insulation?

Concrete screeds take a long time to fully dry out. I have seen
suggestions that traditional screeds generally dry at a rate of 1mm/day
for the first 40mm, and 0.5 mm thereafter after the screed has been
cured for 7 days - so you could easily have to wait 10 weeks or more to
get shot of most of the water depending on the screed thickness.

Adding the insulation will reduce the condensation if there is also some
heating (since warmer air will support more water content before it
precipitates out anyway, and the higher temperature of the internal
surfaces will make it harder for condensation to form in the first
place). Ideally you need to keep the temperature in there above the dew
point all the time. (I find with my (reasonably well insulated)
workshop, that setting a stat at 5 degrees is more than adequate to keep
it dry, and and tools rust free in there)




--
Cheers,

John.

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|-----------------------------------------------------------------|
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\================================================= ================/

On 28/02/2017 00:27, wrote:
On Monday, 27 February 2017 21:14:04 UTC, John Irving wrote:
I've recently built a new workshop in the garden, 5m square. It has a concrete
floor that sits on plastic sheet to stop the damp rising. The walls are timber
framed and clad with shiplap that has been treated externally. There is a
double glazed french window and a double glazed single door. The roof is
canted with an eight inch drop front to back. The whole structure is silicone
sealed and weatherproofed. The roof itself is of corrugated Coroline sheet
with a centre section that is semi opaque plastic sheet. Good enough to let
light in but not completely clear. Condensation is building up badly on the
plastic panels with a small amount on the Coroline. As yet the walls are not
insulated or lined and the floor not yet fitted. The walls are to be clad with
150mm rockwool and the floor with Kingspan blocks with 9mm Sterling board wall
panelling and 13mm T & G chipboard. The concrete was poured the second week in
January so has been down about seven weeks. I intend to insulate and board the
ceiling sections that are of Coroline with a centre section of clear 6mm
sandwich type of plastic panel. Problem is the condensation. Is there a likely
cure or will things improve when the walls and non-centre parts of the ceiling
are insulated. I don't want to do the ceiling insulation if the condensation
is to persist. Does anyone have an answer? Is the concrete cured? How long
does that take? Will the floor benefit from painting before I fit the bearers
and insulation?

Concrete takes about a month to cure, and of course contains a whole lot of water that evaporates slowly.

Concrete achieves maximum strength after 28 days, but it takes longer to
dry out.. One month per each inch of thickness I believe, and that
assumes a DPC was used.

The thing is though that if you spend time in there you will get
condensation at any point where its colder outside than in. I'd suggest some
way to allow it to drain but also allow access just in case.
Brian

--
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wrote in message
...
On Monday, 27 February 2017 21:14:04 UTC, John Irving wrote:
I've recently built a new workshop in the garden, 5m square. It has a
concrete
floor that sits on plastic sheet to stop the damp rising. The walls are
timber
framed and clad with shiplap that has been treated externally. There is a
double glazed french window and a double glazed single door. The roof is
canted with an eight inch drop front to back. The whole structure is
silicone
sealed and weatherproofed. The roof itself is of corrugated Coroline
sheet
with a centre section that is semi opaque plastic sheet. Good enough to
let
light in but not completely clear. Condensation is building up badly on
the
plastic panels with a small amount on the Coroline. As yet the walls are
not
insulated or lined and the floor not yet fitted. The walls are to be clad
with
150mm rockwool and the floor with Kingspan blocks with 9mm Sterling board
wall
panelling and 13mm T & G chipboard. The concrete was poured the second
week in
January so has been down about seven weeks. I intend to insulate and
board the
ceiling sections that are of Coroline with a centre section of clear 6mm
sandwich type of plastic panel. Problem is the condensation. Is there a
likely
cure or will things improve when the walls and non-centre parts of the
ceiling
are insulated. I don't want to do the ceiling insulation if the
condensation
is to persist. Does anyone have an answer? Is the concrete cured? How
long
does that take? Will the floor benefit from painting before I fit the
bearers
and insulation?

Concrete takes about a month to cure, and of course contains a whole lot
of water that evaporates slowly.

I don't see a point painting the concrete, if as you said you already have
a dpm. If there is no dpm then a waterproof finish can help a lot. But
it's still drying out.


NT

On 28/02/2017 01:55, John Rumm wrote:
On 27/02/2017 21:14, John Irving wrote:
I've recently built a new workshop in the garden, 5m square. It has a
concrete

[snip]

January so has been down about seven weeks. I intend to insulate and
board the ceiling sections that are of Coroline with a centre section
of clear 6mm
sandwich type of plastic panel. Problem is the condensation. Is there a
likely cure or will things improve when the walls and non-centre
parts of the
ceiling are insulated. I don't want to do the ceiling insulation if the
condensation is to persist. Does anyone have an answer? Is the
concrete cured? How long
does that take? Will the floor benefit from painting before I fit the
bearers and insulation?

Concrete screeds take a long time to fully dry out. I have seen
suggestions that traditional screeds generally dry at a rate of 1mm/day
for the first 40mm, and 0.5 mm thereafter after the screed has been
cured for 7 days - so you could easily have to wait 10 weeks or more to
get shot of most of the water depending on the screed thickness.

Adding the insulation will reduce the condensation if there is also some
heating (since warmer air will support more water content before it
precipitates out anyway, and the higher temperature of the internal
surfaces will make it harder for condensation to form in the first
place). Ideally you need to keep the temperature in there above the dew
point all the time. (I find with my (reasonably well insulated)
workshop, that setting a stat at 5 degrees is more than adequate to keep
it dry, and and tools rust free in there)

Assuming there is no heating yet, would the OP be wise to allow some
ventilation by opening the windows?

Or install a dehumidifier.

On 28/02/2017 20:01, GB wrote:
Assuming there is no heating yet, would the OP be wise to allow some
ventilation by opening the windows?

Or install a dehumidifier.

Apart from using the above I wonder if it can be eliminated completely.

From my shed door I have an extended corrugated plastic sheet roof,
garden fence one side and open on the 2 others, some mornings it is like
a shower underneath it and that is well ventilated being outside.

On Tuesday, 28 February 2017 20:01:20 UTC, GB wrote:
On 28/02/2017 01:55, John Rumm wrote:
On 27/02/2017 21:14, John Irving wrote:
I've recently built a new workshop in the garden, 5m square. It has a
concrete

[snip]

January so has been down about seven weeks. I intend to insulate and
board the ceiling sections that are of Coroline with a centre section
of clear 6mm
sandwich type of plastic panel. Problem is the condensation. Is there a
likely cure or will things improve when the walls and non-centre
parts of the
ceiling are insulated. I don't want to do the ceiling insulation if the
condensation is to persist. Does anyone have an answer? Is the
concrete cured? How long
does that take? Will the floor benefit from painting before I fit the
bearers and insulation?

Concrete screeds take a long time to fully dry out. I have seen
suggestions that traditional screeds generally dry at a rate of 1mm/day
for the first 40mm, and 0.5 mm thereafter after the screed has been
cured for 7 days - so you could easily have to wait 10 weeks or more to
get shot of most of the water depending on the screed thickness.

Adding the insulation will reduce the condensation if there is also some
heating (since warmer air will support more water content before it
precipitates out anyway, and the higher temperature of the internal
surfaces will make it harder for condensation to form in the first
place). Ideally you need to keep the temperature in there above the dew
point all the time. (I find with my (reasonably well insulated)
workshop, that setting a stat at 5 degrees is more than adequate to keep
it dry, and and tools rust free in there)

Assuming there is no heating yet, would the OP be wise to allow some
ventilation by opening the windows?

Or install a dehumidifier.

You could, but it sounds like it's dehumidifiying itself the free & slow way.


NT