Master Bathroom Hardwood Floor

This page describes one of the phases of the multi-year Master Bathroom Remodeling Project.

Story

Before, view toward sink.

On moving into our house, we inherited rugs in our bathrooms. Rugs in bathrooms are generally considered a bad idea and for some obvious reasons. Over the years we had removed most of these rugs with the exception of the master bathroom. However, we did replace the part of the master bath by the toilet and shower with tiles, so the only remaining rug was by the sinks. Replacing the rug was a major part of the plans for the Bathroom Remodel Project.

The original redesign plans called for ceramic tile, but that was changed to putting in hardwood floors for the reasons explained in Bathroom Floor Tiles Page. Most of the bathroom redesign was completed years before we finally got around to doing this floor phase of the project.

Rug Removal

Initial view of rug being pulled up.

Partial removal of rug padding.

Rug after removal.

Rug remnants due to newer door installation.

We had a new exterior door put in while the carpet existed which resulted in us finding out how the installed cut some corners, or they possibly just not very thoughtful. They installed the threshold over the carpet and that created a bunch of extra work to dig out the hard-to-extract rug parts.

Carpet tacks on concrete slabs are a stupid idea. They fit into the general category of construction techniques that are easy for the builder, but ignore the future and becomes a pain for the maintainer. They nail down the carpet tacks into the slab and the only way to remove them takes some brute force and result in removing a big chunk out of the slab, compromising its integrity. Part of the criteria for any installation should be considering easy it will be to undo it (when the likelihood of needing to undo it is high).

Carpet tack demolition.

Gouges in slab from carpet tack removal.

Closeup of divot left from removing carpet tacks.

Raw slab after rug and padding removal.

Raw slab after rug and padding removal (portrait).

Floor Level Measurement

We would be installed a "floating" hardwood floor, which means it is neither glued or nailed down, simply using its weight to hold itself in place. Since it just lays on the slab, the slab needs to be level enough so that you do not have large gaps that will flex when you step on them. The recommended level tolerances are 3/16 inch over 10 feet. When we did the same style floating hardwood floor for our closet, we did not put any effort into leveling the floor, even though we measured a few areas that did not meet this tolerance. There was some regret afterwards as we had one spot that you could feel would have some bounce when you step on it. The uneven, bouncy floor would be an indication of an amateur job, which I guess it was. For this bathroom project, I really did not want any bouncy parts, so was determined to get the slab within the recommended tolerances.

Using a long straight edge (a level in this case), we went around the floor marking the high and low spots with chaulk.

Floor marked up with high and low spots.

Level and graduated shim for marking floor.

Floor markings about leveling near door.

Measuring floor level gaps.

After a while, I realized we needed a better way to meaure the gaps and created a shim/wedge with graduated markings. This made things go much quicker.

After finished the survey, we found 3 to 4 areas that were out of the recommended leveling tolerance. Although determined to get the floor within tolerance, I knew that leveling a concrete floor was usually a fairly involved process.

Floor Leveling Fail: Self Leveling Compound

One method for leveling a concrete slab is with a special surface grinder. You can rent these machines, but they are bulky and would not be able to get to much of the floor due to its odd shape with lots of nooks and crannies. The other method is to use self-leveling compound, which seemed (and was) tricky to use. Because I had no experience with the self-leveling compound, I was very reluctant to go down that path, but after watching a bunch of videos, I developed a false sense of security in my ability to pull this off. Off to the store I went to buy the materials to start this ill-fated journey.

Bottle of primer for self leveling compound.

Step one in using self-leveling compound is to prepare the floor by sweeping and mopping, then you need to apply a special primer to the floor to help the compound adhere to the slab. The primer had a pleasant blue color as if happy times were ahead.

The self-leveling compound is a concrete product with some plastic-y stuff included, but it it will become and integral part of the slab once it cures. Thus, undoing this was not going to be an option.

Primer for leveling compound drying.

Primer for leveling compound.

After primer for leveling compound had dried.

Bag of self leveling compound.

The self-leveling compound itself comes as a powder in a bag and is mixed with water just like other masonry products. However, the ratio of water used is much more important here (according to the manufacturer and Internet), so we were careful to tightly control the mixture quantities.

Armed with squeegees and other implements for spreading the compound, then with some trepidation, I took the plunge and began pouring and spreading the mixture. The working time was advertised to be about 20 minutes, which was lot a lot of time to do the entire floor, so there was time pressure too.

Wet leveling compound (landscape)

Leveling compound applied and still wet.

Still wet leveling compound (closeup).

As advertised, the self-leveling compound dries relatively fast and they say you can walk on it after just a few hours. As I applied it, I could see some uneven spots while initially spreading it. However, the idea of this compound is for it to naturally flow and let gravity do its work to smooth things out.

Partially dry leveling compound.

Drying in progress for leveling compound (portrait).

Drying in progress for leveling compound (landscape).

Once dried, I was optimistic. The surface had a pleasing grey color and soft-ish texture as compared to the concrete slab. Some areas even looked very smooth. This optimism wore off though and I began to see more and more blemished and uneven areas. The remaining optimism was around all these blemish and wavy areas being more visual and that the actual gaps would be within the needed tolerance. A wood plank can span gaps to some extent, so the floor did not need to be glass smooth, just smooth in a coarser, aggregate view.

After leveling compound has dried.

After leveling compound has dried (closeup).

Dried leveling compound (portrait).

What we needed to do was to re-measure the floor to see if we were in tolerances. Given a do-over was not possible, I started to hope that in the worst case, at least I did not make things worse. And in the best case, even if not as smooth as I hoped, at least it was a bit better than was there before.

Dried leveling compound (landscape).

Closeup of uneven, dried leveling compound.

Temporary threshold wood to prevent leveling compound advancement.

Regrets

And so we came to the low point of the project where we found that the floor was no better, and in a couple places was a bit worse than before. I should have went with my first instincts about this being a risky plan. There were many waves and forms of regret over this decision.

I am pretty sure I know what the mistake was. The instructions talk about the dependencies on how thickly the compound should be applied, and it has some minimum recommendations of a 1/4", but normally people put this on much thicker. I did not want to raise the bathroom floor significantly so was targeting the minimum thickness. The problem is that the thinner it is, the faster it dries and the less time gravity has to do its work to help it self-level. Generally, at the thicknesses I applied it, it was drying faster than it could level itself. Someone experienced with this would know that to be a most obvious problem. When I had my initial feelings of this being tricky, it was exactly due to not knowing things like this. My advice if you use this compound is to only use it on smaller areas and make it as thick as you can to given maximum leveling time. Shower stalls are the typical use case.

I was still determined to not have a bouncy floor, but how to fix the floor was the question.

Floor Leveling Fail: Grinder

Diamond disc and dust cover for power grinder.

Power grinder.

My goal now was a salvage operation and to just get rid of the very worst high spots. I had a hand grinder, so I thought with the right attachment, I could knock down those high spots.

Grinding concrete kicks up an incredible amount of dust, so I would need to consider that in sealing things off and investing in a vacuum attachment for the grinder.

I did not have the right adapter to reduce the vacuum hose tube, so I decided to make one out of some spare attachments I had lying around. Naturally, duct tape was involved.

Sacrificial vacuum attachment for grinder dust shield.

Makeshift vacuum reducer for grinder dust shield

Makeshift vacuum adapter for grinder.

With the grinder set up and ready for action, I sealed off the bathroom, grabbed a dust mask and was ready.

Diamond grinding disc installed.

Grinder setup, ready to go.

Masking door before starting grinding.

The grinding lasted all of 5 minutes. My first gentle touch of the grinder to a high spot in a corner immediately ran into two problem:

It cut way too fast: I was down to the slab in an instant.
Keeping the griding head level was going to be impossible.

With little ability to control the depth or level, this was not going to be an option.

Floor Leveling Success: Hand Sanding

Closeup of the hand sanding block: Rub Brick

With few other options, I went back to researching what we could do and ran across the concept of a "Rub Block". This is a 20 grit, pumice stone-like material with a handle. This is not usually used to level floors, but is used to knock down ridges and excess from concrete.

Floor marked for high spots for hand sanding.

Before taking the power tool approach, my wife had suggested hand sanding the floor to level. That seemed like an incredible amount of work as to not be feasible, not to mentioned how much sandpaper such an operation would consume. Yet now, here were were, about to hand sand the entire bathroom floor (all 80 square feet of it).

Dust and cleanup equipment from hand sanding the floor.

Scoured floor after hand sanding with rub block.

Hand sanding in progress: sanding block and dust.

Three months later and my arm is still not quite right from all that hand sanding. The good news is that it was relatively successful. We made 3 passes at it as I gradually moved my thinking from it being a salvage operation to making it an overall improvement from its initial level condition.

Installation Preparation

Foam filling big gap between slab and wall.

Since we were done with the demolition phase and now moving into the installation phase, we needed to first clean and prep the floor and adjacent wall areas. This included sweeping, vacuuming and pulling out nails from the previous molding.

A surprise we had was that the concrete slab ends under the vanity area by the sinks. And with a gap in the wallboard, there was a sizeable gap going into some unknown underground hollow. We used some foam sealant to ensure no critters from the outside would make their way into the bathroom.

Vapor Barrier

Vapor barrier packaging.

Although many people do not realize it, concrete is very porous and absorbs a lot of moisture. Moisture is bad for wood, making it warp, mold and/or decay. Thus, if you want to install wood on top of a concrete slab, you need to install a vapor barrier to prevent the moisture in the concrete from making its way into the wood.

"Vapor Barrier" is a fancy word for "a piece of plastic". It does need to be of a certain minimum thickness, and you have to be extra careful around the seams.

Starting to lay down vapor barrier.

Vapor barrier installation by tricky tub curves.

After vapor barrier installed.

At the seams, to ensure moisture does not leak through, you need to always overlap the plastic by a minimum of 6 inches, and then use special tape to seal the seam.

Vapor barrier closeup around tub.

Vapor barrier installed, view toward shower area.

Vapor barier closeup by vanity.

Padding

Padding and vapor barrier packaging.

You could put the wood floor down on the vapor barrier, but it is much better to put a layer of padding down. The padding will soften the feel of the floor and cut down on noise.

The padding we used has a beautiful green color too: it is a shame no one gets to see that. It also has some adhesive strips on the ends to join one to the other. This makes the padding act like a whole piece and prevents any movement, especially during the process of installing the wood planks.

Padding installed, view toward shower.

After padding installed (portrait).

Padding installed (landscape).

Floor Wood Selection

We went with what they call an "engineered hardwood" floor. In this context, what "engineered" means is that it is plywood. Plywood does not have the sexiest reputation. Regular hardwood floors are solid wood and therefore more subject to warping especially in moist conditions. Plywood is much more stable and tolerant of moisture. Besides an extra safety against the moisture coming from the concrete slab, it also helps since this is still near sinks and a tub (which seldom used).

I preferred engineered hardwood over laminate flooring even though laminate flooring performs better in moist conditions. I like the idea of real wood, especially in the context of all the real mahogany that is in the bathroom. Though effectively plywood, the top 1/8 inch or so is a layer of actual wood, and that is the only part that you actually see or step on. It would be very hard to visually differentiate between a true hardwood floor and an engineered one after installation.

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Simulated floor: Oak

Simulated floor: Cherry

The engineered hardwood products come in a variety of wood species. Using an image of the bathroom and the Blender 3D modeling software, I experimented with how the bathroom would look with different type of wood. At first, I thought a mahogany floor to match the ceiling mahogany would be too dark and be too much of one material. After looking at these simulated renderings, I changed my mind and went with Mahogany.

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Simulated floor: Maple

Simulated floor: Birch

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Simulated floor: Mahogany

Unfortunately, there are no companies making engineered hardwood floors out of mahogany. And only one makes anything close. The one we went with is called "Santos Mahogany", but it is not actually mahogany (it is in an entirely different family). Honduran mahogany is the gold standard, with African mahogany being a cheaper but acceptable substitute. Santos mahogany is is just similar in coloring and appearance, though it does have the properly of being harder than real mahogany, which is helpful in a flooring application. Still, overall, the color is a bit off and the result not as ideal as I would have liked.

Boxes of engineered hardwood.

Unopened boxes of engineered hardwood.

Given the odd shape of the bathroom, estimating how much flooring I needed was tricky. You have to account for waste, but the more intricate angles you have, then more waste you usually generate. Also, from our previous experience with the closet floor, the manufacturer often has some duds in their boxes (blemished or warped). From my calculations, four boxes would have been plenty, but 3 boxes would probably work if there was not too much waste and bad boards. At more than $250 a box, I decided to risk going with just 3 boxes, which wound up being just about enough, though it was close.

Layout Planning

There are a number of factors which result in the need to plan the board layout before you begin the installation.

A warped floor board.

Since the surface layer of engineered hardwood is actually real wood, you have all the same coloring variations any natural wood has. You do not want patches of light and dark, so you want to mix the boards so the coloring is spread out.
You also need to consider where the seams will be since too many adjacent seams on adjacent boards will draw your eye, be a distraction and cause it to lose the more organic, random look.
The manufacturer's boxes do not come with standard length pieces. They only guaranteed a minimum and maximum length, and each box is unique into exactly what lengths you have to work with.
Some of the boards may have unsightly blemishes and some boards may be warped.

Laying our boards on old rug in garage.

Beginning layout planning of boards in garage.

I used the old, pulled up carpet since it already had the exact dimensions and shape of the bathroom. I laid this in the garage and started unpacking the boxes and arranging them to consider all those layout issues discussed above.

(Side note: only after putting the old rug in the garage did I notice that it has a somewhat Texas-like shape to it.)

Beginning board layout planning in garage.

Partial layout of boards in garage.

Full layout planning of boards in garage.

Because the board are real wood, expanding and contracting due to temperature and humidity (moisture), you want them to be acclimated to the climate before installing them. My garage has a climate that is the same as being outdoors, while inside is air conditioned and heated. Thus, after laying out the boards, I needed to move them inside to acclimate for a couple days before installing them. The problem was that I do not have the space to lay them out fully inside as in the garage.

Color board layout encoding (closeup).

I needed a system to mark where the boards would go so I could stage the boards and know which ones went where. I used colored post-it notes to set the row ordering, and tore off pieces to set the ordering within the row. The colors went in sequence with a Roy G. Biv ordering, and the tearing encoded how many boards and which order they went in for that row: left-most piece at top and right-most at bottom.

I stacked them for each full set of colors and then just had to maintain the stack ordering which was much more compact for moving inside.

Final board layout plan and color colded in garage.

Color board layout encoding, ready to be moved inside.

Indoor staging area for floor boards.

Board Alignment

There was one more important layout issue that required planning. If you just start laying the row of boards down from one to another, you can get to the last row and find you need a thin sliver of a board to fill the remaining space. Having a very thin board is both visually unappealing as well and not having the best structural integrity. Therefore, before you lay down the first row, you need to know how thick the last row will need be. If it is too small, then you are better off ripping down the first board to be thinner, thereby requiring the last row to be thicker. Splitting the difference is ideal where the first row is as wide as the last row.

This first/last row board planning is not too complicated if the room is a rectangle. However, the odd shape of the bathroom means that the "too thin" row issue comes up every time there is an area that transitions to needing a longer or shorter board. In this case, one board will need to be cut down its length since it will be partly in areas of two different lengths. You do not want that cut to leave just a sliver of wood for all the same reasons previously mentioned.

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Using Blender to plan board spacing.

To plan around potential "too thin" problems, I used the Blender modeling software to plan out the best row alignment that resulted in having no thin board areas. I layered a grid of the board rows over the precisely modeled shape of the bathroom and then moved the grid left and right to find where each row edge lined up. This would then tell me how thick I should make the first row.

I got somewhat lucky that I could find a position that left no thin boards. With slightly different dimensions, there may have been no good alignment. However, I could also not put 100% faith into my model. Though I tried to measure accurately, errors would be there and even while installing, each row might not match their theoretical width as modeled. Thus, by the time we had installed many rows in, all the model errors could add up and leave me with a thinner piece than planned. I accounted for this by trying to find the alignment that was the furthest away from "too thin" that I could at all 5 transition points.

Floor Board Installation

Nailing or gluing are some common ways to install hardwood floors. Nailing into concrete is neither desired or recommended and gluing means it will be harder to uninstall. The alternative we went with was too install it "floating". Though in a climate-controlled, indoor environment, the temperature and humidity will still vary and that means the wood will expand and contract. If nailed or glued, these expansion and contraction stresses are born by the nails or glue which prevent the boards from moving very much. But with a floating floor, this means the boards need to be able to move. If they expand and start to push against the walls, the boards with buckle.

First board row completed.

Thus, you have to ensure you leave a gap around all the walls. How much of a gap depends on the room size (larger rooms means more expansion potential). For this small-ish room I used wood block spacers 5/16" thick, which was probably larger than needed.

Note that as long as everything is normal, the board movement will not come anywhere close to expanding 5/8" (2 X 5/16"). However, air conditioners fail and power grids can fail, so you need to plan for more extreme temperatures that might happen. Otherwise, instead of one problem related to the A/C unit or a power outage, you will now have another repair job on your hands.

Taping after gluing (closeup).

Some engineered hardwood floors come with specially milled interlocking edges that allow you to snap them into place. The shapes of the edges form a mechanical hold so that you do not need to apply glue to them. Tongue and groove hardwood planks interconnect, but they do not lock together, so require glue to ensure they do not separate over time. As previously mentioned, for a mahogany-looking floor, we had exactly one product choice and this happened to be tongue and groove. Thus, gluing was needed.

Glue has moisture in it and wood expands when exposed to moisture. To counteract the wood's expansion and glue joint growing, clamps are used. In the context of a hardwood floor, we used painter's tape to prevent the boards from separating while the glue is drying.

Tapping block closeup.

When gluing boards together, you want them to be as close as possible. This has a much better appearance and reduces the chances of debris or moisture getting inside. Variations and imperfections of the manufacturing process means it is sometimes hard to push the boards squarely together with your hands. A "tapping block" is used along with a rubber mallet to aid in seating the boards better. They sell these, but it was easy enough to make one out of a scrap piece that would have the exact cross section so as not to damage the tongues while tapping.

First four rows installed.

The final consideration in the floor board installation is the use of weights to hold the floor down while the glue is drying. There can be imperfections that result in the boards not always being perfectly flush to one another and you do not want the glued joint to reflect that imperfection. Thus, weights are used to push it down to the floor to ensure it is as flat as possible. For us, the weights were plastic, water-filled containers.

Halfway mark for floor board install (landscape).

Almost finished with board install.

Closeup of board gap with tub.

Completed floor after removing weights and tape.

Post install view (portrait).

After install, view toward tub.

After installation, view toward tub.

After install, view toward door.

Molding

All that was left now, after letting the glue dry, was the trim: molding and door thresholds. We needed a combination of shoe molding for the cabinet and tub areas with some baseboard molding for the wall areas. For normal rectangular rooms with a single, uniform floor material, this is a simple task. For this bathroom, it was much more complicated.

Molding by cabinet and tub corner.

Curved molding around tub.

The first complication was the tub, which is an irregular oval and not something I wanted to nail into. I took a chance on some vinyl, flexible molding I found online. It had an adhesive backing and could be painted. I estimated a 50/50 chance of this stuff working, but so far the adhesive is holding and it looks OK.

There were some areas that were straightforward, so we did those next.

All molding ready for install.

Painting trim pieces.

Dry fitted shoe molding my door.

Molding transition due to mismatched floor heights.

Molding transition (closeup).

The next complication was the transition from the new floor of the sink/tub area to the existing tiled toilet/shower area. These were not at the same height and the baseboard molding by the tiles was not exactly the same height as the newer molding. I did rounded over sanding at the edge to make this as little noticeable as possible.

Curved wall molding planning.

View showing extent of curved wall.

The last complication is that one of the walls is curved. The molding was not flexible enough to bend it to this curve without some help. I employed a trick I saw when I removed the previous molding many years before. This trick was to cut a series for slots on the backside, not all the way, but most of the way through the board. This leaves the face of the molding fairly thin and flexible.

Table saw setup for slotting curved baseboard.

Slotting curved baseboard in progress.

Finished slots for curved baseboard pieces.

Door Thresholds

The last step was to install the trim pieces for the two door way transitions: from the carpeted hallway into the bathroom and from the sink/tub area to the tiled toilet/shower area.

Shower area threshold.

Doorway threshold from bathroom.

I had actually custom made these thresholds many years before in anticipation of this project. I needed to make one for the master bedroom closet and used the same cutting setup to make two additional ones out of mahogany. They sat unfinished in my garage for many year and were finally going to have their moment.

I did need to make one modification to account for the differences in height between the tile and hardwood floors. This adjustment was to glue an extra spacer piece on the tile-side of the threshold piece before sanding and cutting.