Underlay for slight damp

Hello and good evening I would use a dpm underlay damp proof membrane we also can provide this or have a look in diy store

No carpet or underlay would be suitable for this. You need to identify the source of the problem; let the area dry out thoroughly then monitor to see if it was a 'temporary' issue or long term. If it's dry, then a PU underlay is ideal for the carpet to be relaid. Alternatively, have a liquid DPM installed, smoothing compound then Luxury Vinyl Planks/Tiles laid. Damp and leaks need to be taken seriously regardless of whether they are 'temporary' or not. Remember that it takes ages for leaks and water based problems to show plus water takes the easiest route so sometimes it's not the most nearest/obvious thing that is the cause. That said, it doesn't mean you have to tear up your house, move out or drastic measures. Good luck.

Use the foam underlay and tape it together at the joints (I'd use duct tape) leave it about an inch short around the edges of the room and allow for a decent size gap along the walls if your using laminate.

While the previous guys are on the right page,DPM is a membrane that is applied with a roller. It isn’t a underlay. Underlays are normally rubber foam or felt. Most underlays will end up soaking up the damp. This will leave a damp smell in the room. There are many underlays on the market now designed for all subfloors, including but not exclusive to, wood floors concrete, floors with underfloor heating, soundproofing and so on. DPM would solve the issues of damp, but if you want a quick fix put a heavy 100 ounce+ (12-15 mm) felt or rubber down. Far better than a foam. That’s what I’d use in my house.