brown/dark spots appeared on newly skimmed ceiling?

[Mr Fix It]

hi all,

i noticed these yesterday when i applied my mist coat. i seem to have approx. 10no. brown spots the size of a 10p on newly skimmed walls.

it was skimmed just over 2 and a bit weeks ago.

i did plan on applying top coat today but just wanted to check - should i stainblock/undercoat these areas first? i will of course get in the loft space just to make sure nothings going on up there but thought id see if anyone has had this before and if anyone knows a good remedy before i apply finish coat? its not on any newly skimmed walls though?!

help....

thanks

 

[TheDec]

You will need to seal them before you Emulsion, an oil based undercoat should be fine or an Alkali resisting Primer.

Dec

 

[joe-90]

They are probably from nails going rusty under the plaster skim. That's why we use galvanised nails, but someone obviously hasn't.

 

[Mr Fix It]

i went to wickes and got crown's ' undercoat primer/stainblock' which i applied a few hours ago but it wasnt covering the spots?! should it have covered it up or will it not show through when i put the top white coat on in a few days time? just dont want it showing through when i put the top coat on.

should i get a stainblock spray and spray them over tomorrow?

 

[TheDec]

And would it happen to be water based?? you need an oil based undercoat.

Dec

 

[Mr Fix It]

And would it happen to be water based?? you need an oil based undercoat.

Dec

it doesnt say on the tin to be honest. i went to b&q, wickes, and homebase and none said 'oil based', but they must do one out of those 3 stockists surely?! they were loads of stainblockers and undercoats though?""

 

[TheDec]

Just have a look on the back of the container to establish whether you clean your brushes with either water or spirit, the latter being oil based, forget the primer undercoats and go for an oil based undercoat.

Dec