dpm under concrete floor

[kitch]

hi all
can anyone tell me when it became common practice to use damp proof membrane under concrete floors?
the reason is i am laying a laminate floor at a house built in 1994 and to my supprise it has ashfalt layed on top of the floor-i wonder if this was done "extra" to the sub floor dpm or instead of the sub floor dpm-surely all houses by 1994 had dpm under the concrete!

 

[noseall]

we've always used a dpm since i joined the trade (1981).

though, back then it was 1000 gauge as opposed to 1200 gauge today.

ashphalt?

 

[kitch]

its either ahfalt or bituman!
its the black stuff
i cant understand why a house built in 94 would have this?
I was just going to lay the laminate and underlay straight on top of the ashfalt/bitumin but im wondering if it possible that no damp proof was put under the concrete?

 

[noseall]

were there any marley floor tiles fitted originally?

it is highly likely you WILL have a dpm.

 

[kitch]

thanks for your replies noseall

im not sure about the tiles,i will ask the guy when i get back there-i thought it would have the dpm,just had to check!
It originally was the show house to the estate it sits on so they have made a special effort for that one