I'm planning on laminating the floor. On the photo attached, where you see a passage between the room and ensuite bathroom. So, do I have to cut the underneath of the doorjamb with a rotary tool or something so that laminate plank goes under it? I've marked in red the jamb spot.
You don't have to, but there's not a great alternative to prevent gaps from showing. An "undercut saw" can be rented cheaply at your local tool rental shop. It's basically a circular saw with the table configured for horizontal cuts. Try to run the blade teeth toward the wood to prevent tearout.
You can also use a fine-toothed handsaw with a scrap of your flooring. Lay the flooring on the subfloor and run the saw on top of it, taking care to not let the saw jump and scar the jamb.
You have 2 options.
- Cut the door jambs and slide your laminate under
- Scribe the door jambs and cut the laminate to fit
1 is much easier than 2. I use a dremel multimax to make such cut. The tool is fairly weak but you only have to cut the decorative moulding (usually a soft material) and that should give you 1/2 to 1" to go under the jambs. Then cutting your laminate doesn't have to be accurate to look good.
But you have to think of how you are going to slide the laminate piece under the door jambs. Don't make this the last row of laminate in your room unless you can slide it in from the adjacent room.
I would do option 2 only if I can't find a way to slide the laminate in.