Basement subfloor, how exactly should I do it?

Question

I am finishing a basement with my father and want to put in a subfloor. I know if there was ever enough water I would probably have to replace the floor anyways but want to give myself a couple inches more so to protect the expensive electronics I will have down there. There is also a sewer access port and two ground rods that stick ~ 2 inches above the concrete floor.

We were originally planning to lay down pressure treated 2x4's the tall way getting us over the two obstructions and build a plywood floor on top of it. After that we were going to build two small access panels in the floor should we ever need to get to them.

An uncle who is a carpenter stopped by this weekend and said if it was his basement he would not even bother building a subfloor. He said the basement was bone dry and it would be a waste. Even if we did get water it would be trapped in between the 2x4's with no way to get it out. The obstructions are in a corner so we would just box them in somehow going that direction.

This now puts me back to planning. I can't see a disadvantage to building a subfloor other than money and height though the ceiling down there is 8ft so height is not an issue.

What is the best way to build the basement subfloor? I have seen other methods such as Dri-Core or Delta-FL also suggested. Ideally I would like to create channels so I could somewhat push water out should I ever have an issue. From concrete to carpet please advise me exactly what I need to do in-between.

Answer 1

I have tried several methods and the best one I have used it foam board on the bottom and 3/4 inch plywood over. I would never lay down wood on the floor. Not only will it rot but it will retain moisture.

Answer 2

Putting wood on the concrete in the basement is typically called "sleepers."

You will, without a doubt, be retaining moisture in this layer beneath the finished floor so a proper barrier is paramount. Also, consider that your basement floor is (or should be!) sloped towards the drain so your sleepers will not be flat for your finished floor.

I have a few suggestions if you intend to proceed:

Use 4x4 instead of 2x4 to make fastening easier into the concrete base

Use a "forgiving" finish floor such as carpeting or tile (as you can level with thinset and/or layers of subflooring)

Sleepers should have a clear path for water to run toward the drain. Never create pockets or lay sleepers perpendicular to the flow of water. This may align sleepers in a "star" pattern out from the drain or maybe you should cut channels in the sleepers to permit water to run

Answer 3

I'm finishing a basement floor that does not have a lot of moisture, but has gotten some water a few times during periods of heavy rain. I'm going to install 1x6 pressure treated decks boards raised off the ground by 3/8" using dense rubber pads. Over the sleepers will be a 6 mil poly vapor barrier and 3/4" Tongue and Groove OSB. I'm going to install a few ventilation vents at the far side of the room from the unfinished furnace room. If we get water I can pull the trim piece under the door to the furnace room and use a fan to blow air under the floor to dry it out. I never want to have to pull out the floor because a little water gets in the basement.

Answer 4

I suggest some reading at buildingscience.com. For example, this one might be helpful: http://www.buildingscience.com/documents/bareports/ba-0309-renovating-your-basment/view?topic=resources/more-topics/homeowner_resources