청마루 (Cheongmaru) Floor Systems

Several have asked questions about the 청마루 floor systems. So as not to distract from other topic post threads, I have started this post for this very specific topic and method.

I can do my best to post specific questions and when time allows I will post a few pictures if I can find them.

Regards,

j

As someone who is completely ignorant of anything and everything having to do with this floor system, would you be so kind as to share some basic information about it such as, pros and cons, materials used, level of difficulty etc? Cheers to the one and only permaCloud

Hi Philip,

Cheers to the one and only permaCloud

LOL...couldn't even think for a few seconds...laughing to hard...Creator please...don't let that moniker stick... Your great Philip!!

...share some basic information about it such as, pros and cons, materials used, level of difficulty etc?

Pros...Hmmm...let me write a book about them (or at least a chapter or two)... That might cover it. There history alone speaks volumes to their greatness!

Cons...well that ties to the subject of "difficulty," as I been told they are too hard to understand or facilitate, but that is really a subjective view...I think they are crazy easy and brilliant because of this easy way about them...However, I have been told, and had reflected to me, as of late, that this too is a subjective view...

So...if you can build a traditional Harvest Trestle Table from green wood (or a small timber frame structure) from scratch...then these floor systems are really very easy to build...If you can't do that, then they could be a bit of a challenge without some guidance. I suppose it is all relative.

Material is just about any wood that could fashion a timber frame...and since most of the timber frames cut in the world (and Korea) are pine (or at least conifer species of some sort) I would say most are that, but any wood can work if you understand the species of wood you work, and how it behaves.

Traditional maru (maru=floor) systems in most Korean vernacular structures are of this form if they are wood, otherwise they are earth, stone or tile...or...one of these and then covered in paper...but that is another post topic...

Hope that painted a bit clearer picture about them.

The photo below is of a 원두막 Wondumak which is a very simple thatched look-out shed or “melon stand” as they are called in Korean. I could just make these for the rest of my life for folks and be a very happy man......they are simply marvelous little structures!! These almost always have a 청마루 to stand on...

Jay C. White Cloud wrote:

Jay,

These photos are forbidden to public access. Can you share them?

Thanks!

Sorry Roger, forgot to make the file permies...

Thanks for the reply!
So, I have a few questions that I couldn't figure out from just looking at pictures. What type of joinery is used? Based on what I can see from the pictures, it looks like the floor is framed like any other timber framed floor and then filled in between the joists with what i'm guessing 5 quarter lumber or something and probably with some joinery that doesn't require nails or screws. How am I doing so far? I'll stop blabbing...

And can you list a few of your favorite pros?

Where can I get a description of how to actually build this type of floor?

PS I've really been digging all your "you need to stop being stupid and learn how to build like the Asians" posts! Seriously... How can I begin to think that I can build something that is better than what they have been doing for hundreds of years. Anyway, keep up the good work and let me know when you have a book translating all your weird character things into English

Well...it looks like a need to fix those photo links...again...I am not sure what is going on???

From what i could gather, the system is quite simple.

It can be seen in images here.
Or in the video here at roughly min. 12.14

The floor can be placed on continuous sub floor (like earthen floor) or over some type of supporting system (joist, etc).
In the image attached, boards type 1 and possibly 2 need to be supported by the existing structural members or can actually be the supporting members themselves.
Board type 4 is larger (why is below) than type 3 boards an lacks one tongue/groove.
Board type 2 is notched (red ellipse) for receiving board 4 after previously placing there one by one all type 3 boards and forcing them horizontally (to the left) until all space is filled.
Board 4 is placed into position and hammered vertically until best fit.

All this can be seen in the video linked.

By and large, this seems like an elegant system.
No nails (the floor just sits there) and no glues.
I gather just about any kind of available wood can be used.
I also thing that doing the tongue and groove is not such a big deal.
It can be done mechanically (by a special tool, maybe powered) or manually (labor intensive).
The system is great since it will allow natural wood movement, expansion/contraction with aging and heat/cold humid/dry cycles.

Excellent researching Ionel...

Let me expand on some points...

The first link isn't a "real" maru system. It is a form of "faux maru" and and simply reflect that standard "t&g" found in most "jointed floors" like "Parquet." Many of these are actually toe-nailed to the substrate, though I have never recommended this practice in traditional work for parquet floors.

The second linked video is an excellent snap shot of floor boards being fitted into the joist and connecting girt beam work of what appears to be a properly fashioned 청마루 in a modern rebuilding style of 한옥 (Hanok).

The floor can be placed on continuous sub floor (like earthen floor) or over some type of supporting system (joist, etc).

Actually, to be a real maru system, it must be fitted into beam work of some form. The other would be something else...like parquet. Also, just floating this on a simple earth or gravel floor without understanding other possible challenges could lead to a very warped and buckled floor. It can be done, but I don't want readers to believe it is as simplistic as just putting a wood floor over an earth floor, which it can be...but not without understanding the different systems, how they work, and how they must be dealt with if they "misbehave" for some reason.

In the image attached, boards type 1 and possibly 2 need to be supported by the existing structural members or can actually be the supporting members themselves. Board type 4 is larger (why is below) than type 3 boards an lacks one tongue/groove. Board type 2 is notched (red ellipse) for receiving board 4 after previously placing there one by one all type 3 boards and forcing them horizontally (to the left) until all space is filled. Board 4 is placed into position and hammered vertically until best fit.

Lets see if I can assist in defining this, having built them...

The only thing that can be an actual board (if it is going to be an actual maru and not simply a "floating" parquet style floor) is #3 and #4, with #4 being your "key" or locking board (these are sometimes jointed with special sliding tenon or toe-nail peg in some very rustic forms of 한옥.) Board #3 can be free tenoned, tongued, or bevel jointed depending on system.

"BEAMS" #1 and #2 are actually the supporting system you speak of. The members that run between posts (there are several regional style of 한옥 (Hanok) with different subtle variances) are a form of "Connecting Girt," what in some European/America timber framing is sometimes call a "Summer Beam," or the "Bent Girt" (but the Asian modalities don't really often follow a "bent system" per se but a grid.)

By and large, this seems like an elegant system...

This is most true, and a very natural way to employ wood with limited ($$) power tools or only hand tools (but labor intensive as stated.) I would point out that there is much more to this process than what is seen in the linked video and photos. I insist that students be able to "read wood" (understand intimately the grain patterns and what they reflect about the piece of wood, how to deal with them, where the top of the tree vs root, where the bark was and the pith is...etc) before attempting such as project as this for themselves, and never doing it for others ($$) unless they have mastered at least the foundation skills of traditional green woodworking.

This is a wondrous craft, but could yield deep and expensive frustration if not understood in its entirety and how the different systems work in concert with one another...For example, you can't tell from these photos how the boards are oriented in the floor. I can tell you from here that some of these "replica Hanok" are being built by Korean "general contractors" and not trained traditional builders as they have lost the traditional (and more enduring) beam and board orientations. These are the nuances that make a traditional system work and modern "reinterpretation" fail or not work properly...

Thanks for clarifying this Jay.
I honestly thought that this system was a form of parquet having different "quality levels".
The "faux" one i thought was the low end and the "real" one the high end.
It's clear now what is what and why.

Regarding wood species, green or dried working and beam/board orientation, i can only have some "i think" but no solid data.
At least over here, easily accessible wood is softwood (mostly pine).
If worked green, upon drying it will warp badly unless there are very controlled drying conditions (not always the case).

Thanks for clarifying this Jay...I honestly thought that this system was a form of parquet having different "quality levels".

Thank you, and I am glad you recognized the similarities to a parquet style floor. You are most correct that a Cheongmaru is not much different than a very heavy, thick and robust "Parquet."

At least over here, easily accessible wood is softwood (mostly pine). If worked green, upon drying it will warp badly unless there are very controlled drying conditions (not always the case).

Pine is an excellent (and globally dominate) species for floors, cabinetry, furniture...and...excellent timber frames. Still today and through history, the majority of it is actually only worked green and the "warping" comes from misapplication and understanding of these ancient modalities of woodworking.

So if a piece of wood is "wrapped badly" it has nothing to do with being "worked green" at all. It does have to do with...how its worked...understanding grain patterns...reading the tree that the wood comes from (if possible to do so) and other subtle finishing techniques like oiling and waxing. Drying too is important as the work does dry "in situ" but this too is dependent on what the item is, as some sections are dried rapidly in fire, there by "case hardening" the wood, while others must dry (or better term..."season") more slowly, or they will indeed warp and blow apart.

I have built chairs, tables, boxes, floors, and entire houses out of nothing but green pine, as have been done for millenia, so it isn't the "greenness" or "wetness" that is the issue...but the approach and techniques improperly applied that can and often is the challenge.

Regards,

j

How can green wood be used for this? Wouldn't the shrinkage cause gaps in the wood?

All -

Mr. Chickadee (Josh) has a two-part set of videos illustrating his implementation of this flooring system in his inimitable style:

Part 1:  

Part 2: