Modular Scratch Building - Part Two

Greetings all!

As promised, I am back to share with you the rest of the build process for a scratch built Foam Core roombox.  I have been very happy with my choice to use Foam Core, and I am impressed with the strength of the final box.  I have not even attached the "ceilings" yet, and the boxes are very sturdy. 

As I posted in the last entry, I did not apply the basswood strips until after having built the basic roombox using Arlene's Tacky Glue along all edges.  I love the Tacky Glue, because it grips almost immediately, allowing you to clamp and move on.  Remember to compensate for the width of your Foam Core board.  It helps to mark the ceiling, floor and the three sides with pencil marks that tell you what they are, because it is VERY easy to glue the back to the front, forgetting to add the sides between! 

Having never built a roombox using this material, I decided to use a framework pattern that surrounded each edge with basswood (or hickory) strips and then filled in the center with additional strips, as you see below.

Wood Strips Added for Strength

This strengthens each edge, and still provides support for the future "floor" of the module above.   I glued at both ends, as well as to the Foam Core along the bottom edge, thus supporting each joint from both sides and from the bottom.   I chose to add full length center supports and then secondary supports to add further strength, similar to a real life build.  I know next to nothing about framing a house, but felt that this would provide the strength necessary.  It proved to be very satisfactory.

At this point I would like to recommend a couple of things about the wood strips.

The first is to use basswood, rather than balsa wood if you buy your wood strips.  I felt that the balsa was just too soft to act as a strong support.  I did use a few balsa wood strips early in my building, and I've not felt that the final roombox is as strong.

The second is DON'T buy them!  Er...I guess I should qualify that.  Don't buy them if you have a table saw and know how to operate it safely.  You can cut those same wood strips for a fraction of the cost.  I used a 1/8 inch thick hickory board bought at Lowe's in 36" lengths, which would be one of the standard lengths of the craft store offered basswood.  Using the table saw and a push stick, I was able to cut the board into strips nearly identical to the basswood strips.

Comparison of craft store basswood (right) and home cut hickory sticks (left)

I have included proof above!  

However, I will caution, you MUST use a push stick, and I recommend using a jig against the guard...basically a board such as a 2' x 4", to keep your hands out of the saw blade...and to support the very thin pieces of wood at the end of the cut.  Always be sure you are operating your saw safely.  But you can save a pile of money by cutting your own boards.  What cost me 15 dollars at the craft store, I could cut for about 5 dollars.  It proved to be worth the trouble for me.

Before applying the hickory sticks to the future ceiling, know what your general floor plan is for both the roombox you are building AND the one above, if you are building a staircase, as I have in my entry.  You will need to cut the opening for the stairwell before applying the sticks, if you do not, you will have an opportunity to do some additional learning...by rebuilding the ceiling!  I've included an example of what I am referring to above.  If I did not cut the stairwell opening, I would have added sticks across the future open area.  So "know where you go".  Always plan ahead..and avoid some of the rebuilding I have had to do!!!

Several of the roomboxes I built also had window boxes attached.

Again, I glued together the window box separately, using just the Foam Core board.  I then cut and added the wood support after the fact.  I used boards around each window and door, and added support between the vertical boards.  Once the boards were attached to the window box on all sides and in the front, I glued the assembly to the larger roombox and applied any additional support I thought necessary.  If you try this yourself, be sure to compensate again, in your measurements, for the width of the Foam Core board in your  measuring.

I treated all sides the same, wood supports on each wall, under the floor and over the ceiling.

Now comes the more interesting part.

I wanted my final house to fit together like a glove, to hold itself together once assembled.  So I created channels on the "inside" walls of each box.  These help align, support, and keep together the final roomboxes.

The grid in between modules within which channels from the next box fit in to

The channels are slightly smaller than the channels they fit into, thus fitting like a glove between the two modules and creating a "single" thickness just like at each end.  

If you look at the third photo above, the one with the stairwell hole cut out, you can see in the photo the way each box nests itself into the next.  Something I neglected to mention above is that I extended each vertical wood support piece about 1/4 inch above the top of the sides, as a mechanism to ensure that the house would fit together vertically, as well as horizontally.

The Ground Floor modules are fit together below, using this method.  On the left side is the Grand Parlor, which we have been following the build of.  In the center is the Entry Hall, and to the right is the Kitchen, Scullery and Butler's Pantry.  More on all of that later!

The three modules making up the ground floor fit together

Don't look too closely at the kitchen behind!  You will know more about me than I want you to!  

I will probably post more on this later as I actually finish the job on the second and third stories.  I got excited and wanted to move on, so I  haven't finished this on those two floors.  So if you are curious regarding more detail of the above, just stay tuned!  I will post as I go, so you will see more, and I will try to remember to take pictures of the process instead of the final products in the future!

Once I have completed all the work I want to complete before attaching the modules together, I will cover the outside with a beautiful light colored brick exterior.  One of the "disadvantages" of building a modular home is that you cannot complete the exterior toward the beginning of the build, but must wait until later in the build to finish it.  There are many advantages though, from ease of transfer to opportunities to hide the wiring between walls. I think it is worth it to postpone the exterior finishing!

Have fun building your own roombox out of Foam Core.   And be sure to be safe while cutting those hickory boards!

Until next time.  

Doug S