laminate flooring

Newbuildago

Just wondering lads must you put plastic and tape it down under the underlay if you laying them on concrete floors? Also how much would the laminate 12mm flooring move over time? Would I be mad 2 have my flooring continous running from da hallbinto the bedrooms, I don't like the look of door saddles and strips to break up the flooring

slimjimmc

Probably not necessary if the concrete moisture level is measured to be within acceptable limits, and the subfloor already has a damp proof membrane underneath it. However for all the little effort and small expense it takes I'd personally do it just in case, e.g a buried heating system pipe leaks.
Laminate shouldn't move much, I guess semi-solid/engineered might move a bit more but in either case always allow the gaps specified by the manufacturer.
What would the longest run be?

Quick-Step's advice is here, up to 15m continuous or 10m from room-hall-room due to rooms being heated differently.

The maximum floor length you can install without expansion joint mainly depends on two things:

the shape of the room in which the floor will be laid
the climate conditions in that room
If the room is more or less square and if there aren’t too many indoor climate changes between weekdays and the weekend or during the day, then you can lay up to 15 running metres without extra expansion joints in the floor surface. The expansion joint along the walls depends on the total length of the floor. For lengths of 15 metres you should foresee an expansion joint of 15 to 20 mm.

It is also recommended to foresee expansion joints under the doors between rooms to separate the rooms. If the floor is laid with a length of more than 10 running metres, from one room to another - across a corridor for example - then this could lead to tension and possible distortion (upward warping) of the floor. This might occur when one room is heated and the other is not or when there is for example a piece of heavy furniture in one of the rooms. We therefore recommend separating some of the rooms from the rest by creating expansion joints under the doors between rooms.

delly

OP, don't cross post your questions on multiple forums please. Thank you.