For the builders/plasterers amongst you (O/T)

[DIFFBROOK]

Around about 6 weeks ago we have had a concrete floor laid in a new conservatory, followed by the walls being plasterd. The plaster appeared to dry out. After a further 2 weeks of dry walls we had floor tiles laid, since then one or two spots of very small damp patches have appeared above the skirting board.

Is this rising damp, or could it be that the walls are still drying out from having the floor laid?

Nb, I watched the builder put a damp course down and air bricks have also been included (with the outside ground being lower)

 

[The Antikythera Mechanism]

I'm a QS by profession, so take what I say with a pinch of salt.

If a dpc and air bricks have been installed correctly it is highly unlikely that the wet patches have been caused by rising damp. Due to the current very cold weather and the likelihood that the temperature in the conservatory is considerably higher than that outside there is the possibility of condensation forming on the walls. This will tend to draw any moisture remaining in the plaster to the surface resulting in isolated damp patches. If you can get hold of an industrial heater, this should be used to dry out the walls and, hopefully, the damp should disappear.

 

[Uncle C]

My guess would be that although the surface of the concrete floor seemed dry, lower down it still contained significant amounts of moisture.

This moisture will need to escape and tiling it will have cut off one escape route. It cant go down through the damproof membrane, so it will slowly work its way up behind the skirting board.

Its a bad time of year to expect things to dry out quickly, but eventually it will clear.

I have found a good way to check if a floor is dry is to place an inverted dinner plate on it for 24 hours. If when you lift the plate there is no sign of moisture (slight darkening of the concrete) you are ready to go.

 

[DIFFBROOK]

I'm a QS by profession, so take what I say with a pinch of salt.

If a dpc and air bricks have been installed correctly it is highly unlikely that the wet patches have been caused by rising damp. Due to the current very cold weather and the likelihood that the temperature in the conservatory is considerably higher than that outside there is the possibility of condensation forming on the walls. This will tend to draw any moisture remaining in the plaster to the surface resulting in isolated damp patches. If you can get hold of an industrial heater, this should be used to dry out the walls and, hopefully, the damp should disappear.

Thanks for that. Thats what I thought, particularly as I watched the guy puting a damp membrane down and he keeps telling me not to block up air bricks etc (which I haven't).

To be honest the very small damp patches have only appeared since this very cold spell and since the floor tiles were laid (i.e last friday), which did result in quite a bit of condensation appearing.

 

[Easy 10]

I have found a good way to check if a floor is dry is to place an inverted dinner plate on it for 24 hours. If when you lift the plate there is no sign of moisture (slight darkening of the concrete) you are ready to go.

Must leave a bit of a mess though.

 

[Uncle C]

Must leave a bit of a mess though.

Stupid boy

 

[Questions]

Thanks for that. Thats what I thought, particularly as I watched the guy puting a damp membrane down and he keeps telling me not to block up air bricks etc (which I haven't).

To be honest the very small damp patches have only appeared since this very cold spell and since the floor tiles were laid (i.e last friday), which did result in quite a bit of condensation appearing.

I cannot see why you would have airbricks in a conservatory wall. Is this a dwarf wall we are talking about.
Airbricks are normally used to either allow an airflow beneath a suspended timber floor or to vent a cavity in a wall.
If you have had a concrete base put down then a period of 4 weeks is often allowed for before anything should go on top of that anyway.

Ring Watchdog now.

 

[BRIGHT ON Q]

I cannot see why you would have airbricks in a conservatory wall. Is this a dwarf wall we are talking about.
Airbricks are normally used to either allow an airflow beneath a suspended timber floor or to vent a cavity in a wall.
If you have had a concrete base put down then a period of 4 weeks is often allowed for before anything should go on top of that anyway.

Ring Watchdog now.

If he has a timber suspended wall in his house they have probably carried it through in the conservatory floor under the concrete to keep the house vented.

 

[Questions]

If he has a timber suspended wall in his house they have probably carried it through in the conservatory floor under the concrete to keep the house vented.

How do you vent under concrete ?

 

[BRIGHT ON Q]

How do you vent under concrete ?

Run a tube (drain down pipe or something similar) from the house vent to the back of the vent in the conservatory.As long as the house floor remains vented.

 

[hitony]

new propertys and new build extentions etc have been experiancing for the last few years or so, what is called "Latent Moisture Content" basically it is the moisture content of the actuall building materials (mortar, wet plaster, bonding for plasterboards etc) taking a lot longer than usual to dry out, the NHBC have put it down to the improved insulation methods used nowadays.

In my last employment I dealt with this on many occasions, it is really nothing to worry about, if possible allow as much natural ventalation as possible, that is easy to say at this time of year as you really dont want to be leaving windows open in sub zero temperatures.

Whatever you do, do not use a de-humidifier, all that will do is shrink everything and you will have gaps on skirtings, architraves and so on.

If you need anymore help, please don't hesitate to PM me, and i will advise as best i can from a distance.

 

[sams dad]

new propertys and new build extentions etc have been experiancing for the last few years or so, what is called "Latent Moisture Content" basically it is the moisture content of the actuall building materials (mortar, wet plaster, bonding for plasterboards etc) taking a lot longer than usual to dry out, the NHBC have put it down to the improved insulation methods used nowadays.

In my last employment I dealt with this on many occasions, it is really nothing to worry about, if possible allow as much natural ventalation as possible, that is easy to say at this time of year as you really dont want to be leaving windows open in sub zero temperatures.

Whatever you do, do not use a de-humidifier, all that will do is shrink everything and you will have gaps on skirtings, architraves and so on.

If you need anymore help, please don't hesitate to PM me, and i will advise as best i can from a distance.

This man knows what he is talking about

 

[Huple]

Run a tube (drain down pipe or something similar) from the house vent to the back of the vent in the conservatory.As long as the house floor remains vented.

Yeah got that but if your airbrick is above floor level, taking it back down and under a concrete slab which runs through level would be a job and a half.
f*** me i do this all day and now I`m talking about it in the evenings.
Help.

 

[BRIGHT ON Q]

Yeah got that but if your airbrick is above floor level, taking it back down and under a concrete slab which runs through level would be a job and a half.
f*** me i do this all day and now I`m talking about it in the evenings.
Help.

It can be a job or it can be easy depending on the air vent heights,sometimes you have to periscope them.

 

[Sir Sarcy]

My cats breath smells of catfood!

 

[hitony]

My cats breath smells of catfood!

I recommend Listerine, or maybe change your cats food.