Alternatives to Cement Piers when building wood floors

We have a room we're planning to convert into a bathroom that has a concrete slab already as the floor. The plan is to add in some piers, some joists and then some wood flooring on top, running the plumbing between the cement and wood floors.

I saw some beautiful work from Jay C Whitecloud recently where has carved piers out of stone, and the joists sit perfectly in them. Wonderful work but a bit outside the scope of this amateur as I've never carved a stone.

I am wondering what alternatives there are to cement which seems to be what is typically sold as piers? It seems to me any wood that comes into contact with cement takes the fast track to rot so we wouldn't want to put our joists right on the slab. How can we lift them up a bit and create some gap so they can breath?

Plastic lumber?
4" pvc?
Water barriers at the base of the concrete piers to abort wicking?
Just some ideas...

I agree with William. There are many things that can be used in between masonry and wood to block moisture transfer.

I've never heard of plastic lumber.

Do you think it would be ok to simply put a layer of birch bark as a moisture barrier between the wood and masonry?

No, you want something that will not rot. Plastic, metal, glass, treated or highly rot-resistant wood.

I see - I thought the problem was that if the wood sits on something that doesn't breath the wood is going to rot, but you're saying the issue is wicking? I would have thought plastic, metal or glass would be no improvement on cement, but I can imagine plastic, metal and glass don't wick.

In our situation here we've got base logs that sit on cement, separated by something that looks like tar sheets. It doesn't seem like it works so well because there is rotting, but then again the house has been neglected before we arrived.

Yes, concrete or masonry in contact with the earth will last longer with a capillary break in any transition to wood. The tar sheets could have worked in theory, but some tar products are still vapor permeable. The more water vapor resistant the better.

Sounds like you could have other moisture problems going on. Is this a crawlspace type situation? Humid air (from outside or inside) could be condensing on the colder surfaces of the base logs. Water vapor from the ground could also be coming into in this small, colder area below the floor and condensing on the base logs.

Carving stone is not that difficult, it is a matter of working slowly until you get the feel of the rock and how it responds to your chisel under the hammer blows. Other than concrete, stone is your best bet for keeping wood from wicking moisture. You can also use stacked stone, which is a very old method and found under most of the houses built in the 1700's particularly in the east (original 13 colonies). You can do dry stack or mortar the stones. even Irish and Scottish Cob houses use stacked stone for the foundation. These houses have no "vapor barrier" or anti wicking material between the rock and wood, they have stood for hundreds of years and unless a problem developed, they are still sound. I've mated poles to the curve of a stone, this is a little trickier than carving the stone to match the wood, but is how the Japanese have done it for at least a thousand years.

Definitely not big enough for a crawl space... unless you're a rodent.

Poor drainage away from the building / foundation for one thing. Plant life had been let to grow all around the edges of the building creating a little micro moisture atmosphere. And over the years the soil had been growing upward that by the time we were here the soil was only a few cm's from the top of the foundation.

With the moisture barriers - is it a different story when using naturally breathing things such as stone or limecrete? Or is a moisture barrier always wanted between wood and stone no matter the kind?

I didn't see your post there Bryant - but you answered my questions already!

What you said makes sense because as far as I know our late ancestors didn't have plastics or metals in abundance to create truly wickless barriers. And I've seen wood places hundreds of years old in far better shape than mine.

The other option I'm wondering about is using natural clay bricks we have as possible piers, stacked and mortared if needed with limecrete. Log joists would just sit loosely on top of these. I'm not sure if it is needed to secure the joists to the pier, or how I would even go about doing that. It seems the way modern builders go about it is the cement pier has a steel connector embedded in and the joists are bolted in place.

When using bricks it is customary to use mortar, this holds them together, the bricks with holes have those holes for straps to keep them in place to the wall they cover. A true brick house would have at least three bricks thick walls made of nothing but brick, The famous Brownstone's are constructed with true brick walls, now to expensive to build. The L bolts (anchors) are a code requirement in most states and actually a good idea, the purpose is to secure everything to the foundation so high, straight line winds won't tumble the building down (the big bad wolf theory). The "Hurricane" clips or ties are designed to hold floor joist to the rim joist and rafters to the top plate for the same reason. Timber Frame Bents now usually have a vertical hole intersected by a horizontal hole so a bolt and washer can hold them in place to meet this code standard. If you are going to use mortar to "bed" your log joist I would use some latex additive to the mix so the mortar doesn't soak up water so much. Jay would perhaps know better than I on that specific, since I've never done that type of sub structure.

Wonderful work but a bit outside the scope of this amateur as I've never carved a stone.

Not as hard (no pun intended...) as many think. Tooling for most of it is under $3K to get started and much can be rented in most areas that are the "diamond bit" portion of the work.

Rob, this is a great query to pose, and thanks for posting it. There is ABSOLUTELY NO REASON to used any form of modernity in this system and most "modern" ways will at the least "maybe" be equal...though I seldom find this to be true in my experience. Concrete, though not really modern, has become so very inferior to the forms found 2000 years ago. It is one of the worst "modern interpretations" of ancient methods I know of...and our failing infrastructure only supports this observation.

Rob, if you can post some pictures and "elevation views" of your intended project, I can perhaps help better. This sounds like a wonderful spot for a Cheongmaru 청마루 system of some form.

I am sorry this conversation got by me...I am here now, should you have any "specifics" you think I (or others) may be able to answer.

Regards,

j

I agree with Jay but as to concrete's strengths and weaknesses it largely depends on the ingredients, installation, and curing details. Lots of concrete being mixed and used today will easily last hundreds of years. As to whether thats good or not I guess it depends.

So how about Osage Orange or Black Locust posts?
As to the stone carving, I have recently found that a diamond blade on a side grinder will work great on the field stone around here(Southern Ohio).
I can carve my initials easily, a groove or socket for a post seems possible with the addition of some hammers and chisels.

I'm no expert on concrete, but so far from my little experience with it I can say i'm not in a hurry to ever use it. Anywhere anything natural is touching it seems to become a mold and fungus factory. I'm sure it has its place, and I can imagine more ancient techniques were less destructive.

Unfortunately, this one room was laid with concrete so it is something I have to deal with. In the photo attached you can see I don't have much room to work with (5.5inch from concrete floor to top of the wood floor to be). I'm guessing whoever did this room wanted tiles in there, but settled for a plastic version of it. The top of that doorway is going to be the top level of the wood floor with the rest of the house.

With such a small amount of vertical space to play with I don't see how there is much room to put piers in while still having room for joists and thick enough planks. Say I use 2 x 4's (5cm x 10cm) joists, then that only leaves 1.5inch (4cm) for piers and floor boards. Being fairly cold climate here I would like as thick of planks as possible for the boards. Mostly what I have found available for floorboards here comes at 1.1-1.3inch (28-33mm). No doubt this comes from mass harvested mono culture forests of either spruce or pine.

The Cheongmaru really does look nice. I wonder how it can be done with much less vertical space like what I have in this room? Or what would be the best practice for putting in a wood floor in this room?

The other option I guess is that we just lay tiles on the cement. This is less desirable though because with the freezing temps here unless we do some radiant heating you wouldn't want to go in there in winter. Perhaps with an insulation layer between the concrete and the tiles it wouldn't be so bad, but then this route will leave all the plumbing exposed above tiles instead of below floorboards.

I'm wondering if whatever the case, wood floor or tiles, should we put some sort of insulation above the concrete to reduce some of that cold coming up into the room? There is a company not far from here that makes breathable insulating fibreboards from pine, without the use of any toxic chemicals, they say. These are 5-7mm thick.

Hey Rob!!

Very exciting project to help you with...thanks so much for sharing it! And a big thanks for the photos...it really helps.

Europe and Asia is well ahead of North America in many respects...like natural insulation. I love it all, and as long as the manufacture will warranty the product for "high humidity areas" (which many will) then you could very well use it in this application.

1. At this point, I would start making CAD (or by had) elevation view models of potential lamellar or stratum system of the way this floor will look...including the concrete layer. I don't think I would remove the material that is currently covering the concrete. Is that some type of "vinyl" of "linoleum" material? Either way, I believe I would leave it there.

2. I would strongly suggest also a properly installed "Radiant Barrier" insulation in this application. In Eesti that would read "peegeladav isolatsioon" or "reflective insulation." I would lay this down first and then 20 mm thick furring strips 500 mm on center to lay your "Isoplaat" board.

Now I probably would design a floating floor system with all wood and/or stone joints, similar to the Korean Maru systems. This can rest on your Isoplaat or you can add more radiant insulation and furring strips to either accommodate a "hydronic system" of more insulation like Mineral wool or the related.

Let me know if I can suggest more, and please post pictures as you progress in this project for others to see. How old is the house, and what is it built from?

Regards,

j

Sorry I almost forgot...

The Cheongmaru really does look nice. I wonder how it can be done with much less vertical space like what I have in this room? Or what would be the best practice for putting in a wood floor in this room?

To go "crazy" all natural...you could just screed in a thick layer of "light straw clay" cobbing materia...50 mm to 100 mm thick, then float a wood floor on this, providing access panels for the piping you may want to run under this new floor system. In "full support" floated floors the board thickness you suggest are more than adequate. You do have to either joint each board by hand or us a tool like this to make it faster, it is called a Domino Jointing Tool.

Thanks a lot for those instructions Jay. I have attempted to create a 3d model to scale of the room with the elements in the order you said. The pictures show side-view, front-view and a perspective view of the layers separated/elevated. See if I understood you correctly.

Yes, you are right that material is some type of vinyl. I was thinking of getting rid of it but if it serves a purpose there I might as well leave it.

A few things I'm not exactly clear on -

When you say '500 mm on center' does that mean to space the furring 500mm apart, with one of the furrings starting in the center?

In regard to the joists, how are they joined to the floor, or do they just rest on the isoplaat? If you look in my diagram, I have run the joists in the opposite direction of the furrings - is that correct? And what sort of spacing should they be placed?

Is the furring there to create an air gap between the reflective insulator layer and the isoplaat?

Finally, with the reflective insulation - would you normally use this material if it wasn't a concrete floor we were working with? Say it was limecrete or cob - would you still use a non-breathing reflective layer in there?

The house is 1930's log house I can't tell what the wood is but it smells like pine or spruce - it is on a stone foundation that was mortared with cement at a later date.

Anything else you could suggest would be a great help!

Yes, you are right that material is some type of vinyl. I was thinking of getting rid of it but if it serves a purpose there I might as well leave it.

I would leave it as part of the current system.

When you say '500 mm on center' does that mean to space the furring 500mm apart, with one of the furrings starting in the center?

Yes, though there are other methods as well depending on materials and joint methods to be employed.

In regard to the joists, how are they joined to the floor, or do they just rest on the isoplaat?

The joist just "float" as a framework that is independent of the rest of the system. It does just rest on whatever is beneath it.

If you look in my diagram, I have run the joists in the opposite direction of the furrings - is that correct? And what sort of spacing should they be placed?

That is fine in this application and the spacing of 300mm to 500mm will be dependant on the method of floor jointing you choose.

Is the furring there to create an air gap between the reflective insulator layer and the isoplaat?

Yes, as this "dead air" space adds considerable R factor to the system.

Finally, with the reflective insulation - would you normally use this material if it wasn't a concrete floor we were working with?

Each job is different depending on project needs, and client desires. It is used very often in your application unless going "all natural."

Say it was limecrete or cob - would you still use a non-breathing reflective layer in there?

Probably not.

Anything else you could suggest would be a great help!

Not at this time...you are doing great understating all of this from what I can tell....Great job. Let me know if I can explain more.

Regards,

j

Thanks a lot for this information Jay.

The joiner might be a bit too pricey for us at this stage - I'm wondering if I might be better off buying pre-cut floor boards that already have full length joints running along them like what they sell here. Do you see a problem with that? I think I can get floorboards for the whole house cheaper than buying a joiner. Really looks like a invaluable tool though.

The many tool professionals use are VERY expensive, and I feel really bad for folks that want to do the work we do but can't afford the tools. Here locally I do a lot of "bartering" with folks like you so they can keep small projects going. The alternative is doing it all traditional...which means cutting those "free tenon" (what Festool calls "domino") into each board by hand with mallet and chisel. I have done it that way too...very...VERY...time consuming. Yet, it is very rewarding work.

The type of boards in the link are called "tongue and groove" jointing. This is very common type of system, but usually relies on being nailed down through the "tongue" section as each board is laid, or through the face...both systems with "cut nail" or "high tech screws."

If you rely on just the "T&G" joint for a "floated floor system...the "wedging" while laying it down and near the final "wall wedge board" is critical. With the "free tenon" system it almost becomes like a floating wooden carpet that is almost monolithic in nature, as the boards can move further apart and still stay "connected" with each other. The boards also have less tendency to "come apart" with the longer tenon than they do just relying on the "tongue."

I know the demand for this tool is high enough that many local DIY folks and some Contractors will buy the machine to do a job and then sell it for almost what they paid for it...kind'a like a rental tool. I will warn you though...if you do "buy it" with thoughts of selling it later...that only happens to about 20% of the users...As this tool and what it saves in time and what it can build...even in greenwood is rather addictive. I have even built (in the past) large slab pine hutches with wood fresh of the saw mill without any nails, screws, or glue just to see how they would work out. They did fine...especially in White Pine, and Cedars. Mortise and Tenon and free tenon joiner is the foundation of woodworking for the last 7000 years for just that reason...

Good luck! Let us know how things progress.

j

Jay, I really do appreciate the purchase of a fine tool and understand how these tools are the path towards greater freedom. The tools that really 'set you free' so to speak, are definitely real commitments though. Things like your own wood mill, to make planks from logs, or even the equipment to get a log out of the forest in the first place is no light decision. It is a bit like making a deal with the devil at the moment while making this process away from the mass production monopoly.

I am really interested in learning how to do mortise and tenon, especially when it comes to logs as we have a few beams that need replacing and I would like to do it properly.

Nothing much to show so far, except we took apart the old sauna due to lots of wood rot, and I salvaged what I could out of the framing to make a couple of quick and dirty solid repurposed Saw horses.

These are what I have new students cut to acquire the basic knowledge of the mortise and tenon joint and the layout modalities of them. I teach "line rule" as apposed to "edge rule" in most of my layout classes, with a solid working knowledge of "scribe rule" methods as well.

That is really beautiful work Jay. Was this done with the Domino joiner? What do you call the mortise and tenon joint with that additional lock in there? Like in this picture with the logs where the tenon goes right through the other side and then has another mortise and tenon in it? And do these tenons just sit in there without any screws or nails?



With creating log mortise and tenons (which I need to do to replace some of the beams in the bathroom and sauna) do you have a tool for these? Do you chisel them by hand or would you say use a circular saw and cut them precisely (this is what I'm thinking of doing at the moment)?