Block pattern on plaster in 14 year old house

[sparkwright]

As the title suggests, can make out the blockwork on the plaster of a 14 year old house on the external walls indoors.

The plaster is traditional wet plaster; ie NOT dot and dab.

It's a bungalow. Cavity insulation is celotex type sheets touching the inner wall, whilst leaving a cavity on the outer wall.

The top of the cavity is blocked with some flimsy plastic sheeting. There is a vent in the floor which ducts out through the wall to the outside.

The blockwork pattern shows the cement joints to be the darker areas on the wall. The plaster feels smooth. It is currently emulsioned, no paper.

What is causing this and can anything be done?

The room is due to be re-emulsioned in a week or so. Should some sort of paint be applied first to prevent the dark lines re-appearing?

Thanks in advance.

EDIT. The floor, as I can make out, is a floating chipboard floor, not sure if there is insulation below that, presumably on a concrete base.

The blockwork is thermalite.

 

[simonjay]

As the title suggests, can make out the blockwork on the plaster of a 14 year old house on the external walls indoors.

The plaster is traditional wet plaster; ie NOT dot and dab.

It's a bungalow. Cavity insulation is celotex type sheets touching the inner wall, whilst leaving a cavity on the outer wall.

The top of the cavity is blocked with some flimsy plastic sheeting. There is a vent in the floor which ducts out through the wall to the outside.

The blockwork pattern shows the cement joints to be the darker areas on the wall. The plaster feels smooth. It is currently emulsioned, no paper.

What is causing this and can anything be done?

The room is due to be re-emulsioned in a week or so. Should some sort of paint be applied first to prevent the dark lines re-appearing?

Thanks in advance.

EDIT. The floor, as I can make out, is a floating chipboard floor, not sure if there is insulation below that, presumably on a concrete base.

The blockwork is thermalite.

The areas where the mortar is will be colder, so it is probably condensation causing very slight dampness there. The colour difference is probably very slight, but the eye is very good at spotting patterns so it tends to stand out.
It *could* be dampness coming through but only if there is a problem with the cavity wall or a leak somewhere.
If its condensation you can try to reduce moisture in the air but the problem might always be present. The only solution might be dry lining. If you took it that far, make sure dot and dabs are in the centre of the blocks or use drywall fixing foam that is insulating by nature.
Simon.