Bat Houses - plans and guide

My home had a swimming pool in the back yard when I bought the property.  It was an "Esther Williams Pool".  It was about 35 ft. long and 15 ft. wide, constructed of California Red Wood 8 quarter stock, and had a vinyl liner fitted within.  The design was a combination of above ground with a diving pit.  Half was 4 feet deep and the other end had a diving pit another 4 feet deep.  It was constructed with a concrete base and plywood sides 4 feet tall topped by a red wood deck that was about 4 feet wide and went all the way around.  After dismantling and removing the structure, I was using the pit to burn yard trash and trying to fill the thing with plaster and lathes from the house during the restoration.  After 20 years, I finally decided to make it a Kio and Gold fish pond.

This has raised the back yard mosquito population greatly.

Not wanting to pour chemicals in the pond to affect the mosquito larva, I finally decided to add a natural predator of the mosquito - the bat.  I searched the internet and found many things to be aware of and how the bat house should look, but nothing really nailed it down or showed me in detail.  So here is how my experience has progressed.

FIRST THING TO REMEMBER IS THE ORDER :  Build the bat house first and then mount it onto the 4x4 post BEFORE you set the post.  Also if you want the post to have a finial on top, then mount this onto the post also, before you stick the project into the post hole.  It is no fun trying to do this while up a ladder about 10 feet off the ground.

Because I have a pledge to trees, I try to never throw away any wood.  If it is too small or damaged, or knotty, or anything... it will help start a fire in the stove this winter and I will be glad I have it then.  A friend made some book cases for a judge and had some barn cypress end cuts that he gave to me about 20 years ago, because he knew I would find a use for them.  So I checked and found two suitable boards 12 3/8" wide and 41" long.  They were rough cut and had never been planed, so thickness was 7/8".  This would do very nicely and it gave me the ability to make the house with two chambers.

I went to LOWE'S and got :

a 12 ft. 4x4 treated post (and wish I had gotten a 16 ft.)

a piece of 1/2" plywood both sides sanded ( 2 ft. x 2 ft. )

a tube of caulking

a can of flat black spray paint

a very small can of polyurethane

a piece of aluminum 8" wide and about 24" long (normally used for roof flanging) to make the roof

you will also need just about 12 - 1 5/8" dry wall screws

about 30 - 2" dry wall screws

2 -  3 1/2" decking screws

and 2 - 1" pan head screws to anchor the roof to the house.

With the first board I decided to have 1 1/2" at the top of the back in order to put a screw through for mounting onto the post, and a 2 1/2" bottom extension that also gives a place to put a second screw for mounting, as well as an area for the bats to land as they enter the house for the day time hours.  This left 37" to divide by two and get 18 1/2" for the box front and resulted in a 22 1/2" back.  Here is a side view of the design:

Here is the bottom to show the chambers.

I cut the plywood 12 3/8" x 18", being careful to have the face grain of the piece running horizontal rather than vertical.  This is because of the grooves that will be cut into the face.  If the grain were running vertical, then the grooves will be perpendicular to the grain and might result in the deterioration of the surface when the bats climb around inside since the surface might chip off and fall out.

The next thing is to cut the groves.  These groves are recommended to be about 1/16" to 1/32" deep, and only the width of your saw blade.  Space them 1/2" apart and be sure that they will be horizontal after the box is complete.  This will result in a ladder effect for the bats to use while climbing around inside.  These groves must be on both sides of the plywood, the back side of the front board, and the front side of the back board.

I made my spacers 1" wide so that allowed me to start the groves 1 1/2" down from the top of the plywood and also the back side of the front board.  On the face of the back board the first grove is 3" down from the top.

These groves are the most time consuming part, but must be cut all the way from the first one down to the bottom of each piece.  The groves at the bottom of the back board are for the landing pad for when the bats are gaining access to the chambers.

With these three pieces finished, you should now use the black spray paint to coat the inner surfaces.  I made the mistake of realizing they were not painted after I finished my project.  I had to spray the chambers like crazy.  Even then I had to tape an arts paint brush to a 2 ft. stick so I could paint the inside surface of the spacers at the top of the inside...no fun.

I used the second piece of cypress to cut a 17 1/2" long piece, then I ripped 6 - 1" wide pieces from that.  Two of these I cut to be 12 3/8" long and the other four remain 17 1/2" long.  Inspect the spacers and determine which of the 7/8" sides will be the surface on the inside of the chambers, then use the spray paint to coat that single side in preparation for the assembly.

Now in my assembly you will notice that I forgot to spray paint before I put the house together, not advised.  If there is a trick to the assemble, you should start with the front board positioned with the outside face down on your table, and the grooved side facing up.  The reason for this is that after you finish your project,  the front will not have the screw heads showing, they will all be in the back, as you will see soon.  Your first attachment is one of the two shorter spacers.  Place it at the top and run a bead of caulk the entire length and near the outer edge.

Now flip it over and use some clamps to squeeze it snug to the board for attachment.  I use a counter sinking drill bit for a 1 5/8" dry wall screw and put three across the spacer, then add the screws.  Make sure the head of the screw is slightly below the surface so it will not be in the way for the next layer to be attached.

The same process is used to attach the side spacers with extra caulk added where they will butt up to the piece across the top.  After each spacer is added, I ran my finger down the side to spread out the caulk that is squeezed out. 

Just for safety, dry fit the plywood on the spacers to be sure of positioning.  I ran a bead of caulk around the outer edge of the spacers that had just been attached in preparation for the plywood, add the plywood and clamp.  Next I added the other shorter spacer at the top making sure as to how it was to be attached and with the bead of caulk added.  I removed the clamps at the top holding the plywood in position, placed the spacer, and then clamped that piece.

Here I will use 2" dry wall screws to go through the new spacers and the plywood into the first spacers, and try to not drill where you put the first screws in the first layer of spacers.  Follow this also to attach the two longer side spacers.  I think I put about 4 screws across the top and maybe 5 on each side spacer. 

Now you are ready to run a bead on the outer edge of the spacers and position the back for clamping and attachment.  I clamped a strip of wood across the top of the back board so that when I placed that piece on the assembly I could just butt the top of the assembly to that strip.  Then be sure the sides are flush and clamp the stack tightly.  Drill the counter sink holes for the dry wall screws and use the 2" screws for the final attachment.

Mark the center of the top and bottom edge, then use a 3/16" drill bit to predrill the hole about 1" from the edge for mounting the house onto the 4x4 post.  Here I used a 3 1/2" coated decking screw to attach the house at the top and the bottom.

If you want to dress the post with a finial at the top, now is the time to fit and attach that also.

I went a step further by typing "batman symbol text" on Google and got a bunch of figures to select one for the symbol added to the front.

It was cut out of the extra from the 1/2" plywood used for the divider.  I attached it using polyurethane glue so it will be water tight and painted it to be noticeable.  Not that the bats will be impressed, but when friends see it they will not ask, "why that big box on the pole?"  At this point I applied the first of three coats of polyurethane. 

While that dried, I worked on the metal roof. I used the aluminum to cut and bend a water proof roof for the bat house.  Notice the small triangles at center of each end.

These are not to be bent until the piece is dry fitted to the bat house.  Also there are 4 small circles containing "x" that represent approximately where the holes will be drilled once you dry fit this to the house.  The solid lines are where you cut with scissors, and the broken lines are where you will bend the metal.

SUGGESTION : Download this diagram, print a copy, and cut and fold it before you try it on the aluminum sheet.  That way you will not make a wrong cut or bend....

This should be cut, bent, and dry fitted before you mount the house to the post.  I trimmed two corners and then started to mark my metal. 

Using my table saw as a drawing table I was able to flush the metal to the table edge and then the combination square was similar to a "T" square for the markings using my awl (ice pick).  Large scissors and QuickClamps are also needed. 

 I marked the slot for the screw through the back and the tall "V"s to be cut out as well as the two lengthwise mark as to where I will make the 90 degree bend and the 27 degree bend.
  

Before I made the first bend, I removed the tall "V"s and the screw slot. 

  

Then clamped the metal to the edge of the saw table and with my fingers moving from end to end, I bend about 5 or 10  degrees at a time as I move from one end to the other.  Then back the other way with another 5 or 10 as the metal will allow.  Once I have about as well as I can do with my hand, I use a helpful tool I made that really sets the 90 degree. 

                                 

Holding this 4 in. block to the metal and tapping it with my hammer as I move it, will make a very nice bend.  Next I cut the metal at the unbent mark for the side extensions of the sloping part. 

  

Then I re-clamp the metal for the 27 degree bend and this is done with my hands only.  When you dry fit the top to the box you will probably make an adjustment to this bend so that it remains in contact with the front edge of the top of the box.  Now with the top fitted to the box you can fold the side extensions of the sloping part flat to the side and you will be able to tell where to make the bend of the "dog ears" that bend around the back edge.

  

After that you will see how the parts fit together to give a nice water tight cover.  Snug these pieces together and drill your hole through the two layers of metal about 1/2 in. from the bottom. 

  

Here you see the cover upside down after the holes have been drilled. 

Here it is fitted and ready.

Also I wanted to avoid having an empty cavity where wasp and bugs could nest and possibly make the bats vacate, so on my band saw, I cut a 2x4 diagonally to make two inserts to fit in the area under the metal roof and on top of the box.

Once you have it right and the polyurethane is all finished, then you are ready to mount the house to the post.  Leave the top screw mounting the house to the post just slightly loose so the back of the metal roof can slip down between the back of the house and the post.  Put a bead of caulk running across the top of the box from side to side and set the fillers into that area.

Once the house is mounted to the post and the top screw is not tightened, you can slip the metal top into place and lift the front edge of the metal very slightly while pushing down on the top and using an extension with your drill driver, tighten the top screw and that will hold the metal tightly.   Next fit the metal on the side and add the 1" screw, for both sides.  Remember, the side extension on the sloping top goes first, then the actual side covers and then the screw.

               

Finally I ran a very generous bead of caulk just under the metal top where it touches the front of the box.  This will also help keep out unwanted pest.

The placement of the post with the house attached is naturally in an open area so limbs and bushes will not make the bats come in for landing on 'a wing and a prayer.'  Mine is right next to my pond because it was suggested in some of my readings that they like a constant source of water.

Another site I found helpful was : http://batmanagement.com/Batcentral/batboxes/whyfail.html. 

Good luck and do your internet searches for more information on bats and what they need and like before you build your bat house and set your post.