There are lots of ways to lay wooden floors in a dollhouse. An inexpensive way is to use Popsicle sticks, skinny sticks, or any other wooden strips you can find. The process of laying a wooden floor isn't hard, but it can be tedious and time consuming. The results are well worth it though.
This picture shows the floor of the Cardinal House. I did a little work on it today. I finished shingling the back of it and I cleaned up so of the exterior slots by filling them with wood fill.
My daughter and I made this floor out of Popsicle sticks. You can buy a huge bag of them from the dollar store or 99 cents store, or the big craft stores. I wanted this floor to look a bit rustic.
I started by cutting the round ends off of each stick. I started using my EZ Cutter for this, but it was a bit bigger job than I wanted to do with that tool. It hurts my hand after a while to use it, so I pulled out my mini cut off saw from Harbor Freight and cut all the ends from the sticks I needed in about 5 minutes. For this floor I made a template out of card stock and glued the wood to the template. When done I simply glued the template to the floor of the house.
Getting back to laying the floor, you need to start out by cutting your sticks in various lengths. I kept mine pretty short for this floor. You want to vary each row so that the end seams of the planks don't line up. You should make sure that the end seam of one row hits the middle (or at least not the end) of another piece in the next row. Real life houses vary these joining points as well.
You can dot each board with glue or lay glue "stripes" on the card stock and lay the pieces down over them. I like to use quick grab glue for this, so dotting each piece is easier for me. The glue dries too quickly to lay it down in stripes. If you use carpenters or tacky glue, the stripes would probably be faster. Make sure to only get glue on the back side you are laying down. If you get glue on the top the stain won't go in and you'll have a bad patch in your floor. White it is drying, you'll need to weigh it down with something heavy. I tend to use books or cans of veggies.
Once it is laid, you sand, and sand, and sand. You want it to feel level and smooth when you run your hand over it. Don't blow away the sanding dust either. This fills in the cracks nicely and helps it look tightly laid. I've been known to keep sawdust from other wood projects to use to fill in the cracks. Rub your sawdust into the cracks.
Then you can stain. Use as many coats of stain you need to get the color you want. I tend to sand in between coats of stain with a paper bag. This sands just enough to get it nice and smooth without tearing up the wood.
Once it is dry I wait at least 24 hours and then seal it with a wood stain sealer. I like a glossy floor so I use several coats, letting each coat dry thoroughly in between. If you've done this on a template, once you've let the sealer dry you can install it in your house.
You can see it's a long process but gives very nice results. This picture on the right is the attic of my childhood Skillcraft house. I used skinny sticks I picked up at Wal-Mart. They go faster because they don't have rounded ends that have to be cut off. They aren't as wide as Popsicle sticks, though. It all depends on the look you want. You can click on it to get a better look.
This house still isn't finished inside. I love the outside, but haven't been motivated to finish the inside. Do you see a pattern? One of these days I'll decide to finish the inside and that will be that.
This picture is the front porch of my childhood Skillcraft house. I used pieces of Greenleaf siding on the porch, and followed the same process as I described above. I think it turned out really nice.
So you see that you can use a variety of wood strips to make a wooden floor. You can also take the wood and add a pattern or a mosaic in your floor. I'll save that for another day.