Wood – Should I put caulk/silicone at base of toilet on hardwood floors

If you remove the P-Trap (the S shaped pipe) from the drain of the sink, then yes, you need to plug that pipe up as well.

The toilet drain has no trap - the toilet itself is the trap, and so it will need to be plugged regardless.

For the drain to the sink, its often easiest to simply affix a permanent cap on the drain pipe and then cut that off when ready to work again, but you need enough of a drain pipe to be able to cut a few inches off later and still work.

For the toilet, you can pick up a toilet drain plug which you can insert into the toilet drain and tighten to form a seal.

There are two primary uses for caulk:

1. aesthetic gap filler
2. functional moisture/air barrier

For the latter, you'd see that wherever you need to waterproof joints (shower panels, exterior windows, etc.)

For the former, it can really be used in any situation where you have two pieces of material meet. Typically this is done when two different materials meet and you want to cover a small gap. Example would be where door trim meets the sheetrock. Higher end finishing would have that caulked before painting.

So, as for these shelves, it's really up to you. One option is to caulk it. Another would be to attach some trim moulding.

As for how to properly caulk, the basic method is:

• cut tip to size
• apply to joint
• smooth to finish

There are tools to smooth it, but I prefer to just use a wet finger (and plenty of paper towels to wipe finger off as you go...)

Note if the gap is too wide, you may need to fill the gap first. I've used foam weather stripping in the past for this.