# Post bat house: Post bat house [View illustrated instructions](https://diyplans.org/plans/post-bat-house/variants/standard) [Plan and other configurations](https://diyplans.org/plans/post-bat-house.md) Build a wooden bat roost. ## License [CC BY-NC-SA 4.0 International](https://creativecommons.org/licenses/by-nc-sa/4.0/). You may share and adapt this free design for noncommercial purposes with appropriate credit, a link to the license, an indication of changes, and the same license on adaptations. See [the FAQ](https://diyplans.org/faq#license) for details and exceptions. Revision: 1 Status: published Difficulty: intermediate ## Before you start - Read the complete cut list and dry-fit the assembly before fastening. Wear eye and hearing protection and control wood dust. - Use untreated wood with rough roosting surfaces. Leave interiors and exposed landing surfaces unpainted; do not add plastic mesh. - Choose exterior water-based finish shade for the local summer climate. Provide shade or a suitable alternative roost where overheating is possible. - Plan at least 12 ft of clear space below the entrance and a clear flight path. Confirm access, mounting support and maintenance access before building. ## Dimensions - Outside shell width and depth: 6 1/2 in - Shell low height: 36 in - Roost gap: 3/4 in - Entrance above modeled ground: 12 ft ## Shopping list One complete configuration, with stock allocation and allowance for saw kerf. Unused stock remains for other projects. - 1 piece: Untreated naturally durable cedar post, 4x4 x18 ft actual 3 1/2 square. Special-order straight stock; structural support approval required before purchase. Do not splice shorter stock. - 1 piece: Untreated cedar, 1x6 x8 ft. Rip 5 wide; cut front/back 37 1/2 blanks then bevel to dimensions. Use offcuts for spacers. - 1 piece: Untreated cedar, 1x8 x8 ft. Rip 6 1/2 wide; two 37 1/2 blanks then slope to 36/37 5/16. - 1 piece: Untreated cedar, 1x10 x2 ft. Rip 8 across; cut 8 3/16 along slope with end bevels. - 1 piece: Exterior screws, No.8 x1 5/8 in, box50 - 1 piece: Exterior screws, No.8 x1 3/4 in, box25 - 4 pieces: Corrosion-resistant lag screws with washers, 1/4 x3 in. Front/back screws are staggered vertically;1 1/2 in penetration into post. - 1 piece: Exterior paintable sealant, 10 oz cartridge - 1 piece: Exterior water-based primer and finish, 1 quart finish plus primer per label. No chemical treatment or coating on roosting wood. - 1 piece: Corrosion-resistant roof flashing, 10 x10 in blank. Form to roof with drip edges; protect sharp edges. ### Required installation supplies - Have a competent local installer verify the 18 ft post, wind resistance, soil/frost conditions, foundation, raising equipment and long-term untreated ground-contact durability before purchase and installation. - Obtain site-specific footing and temporary support supplies from that design. No footing quantity or structural capacity is implied. ## Materials in the model Installed wooden parts from the matching CAD; fasteners and finishes are separately purchased. - Post / Untreated 4x4 cedar, actual 3 1/2 square; 18 ft blank: 1 installed pieces - Front\_lower\_spacer / 3/4 thick cedar offcuts: 1 installed pieces - Front\_upper\_spacer / 3/4 thick cedar offcuts: 1 installed pieces - Back\_lower\_spacer / 3/4 thick cedar offcuts: 1 installed pieces - Back\_upper\_spacer / 3/4 thick cedar offcuts: 1 installed pieces - Front / 1x6 cedar ripped to 5 in: 1 installed pieces - Back / 1x6 cedar ripped to 5 in: 1 installed pieces - Left / 1x8 cedar ripped to 6 1/2 in: 1 installed pieces - Right / 1x8 cedar ripped to 6 1/2 in: 1 installed pieces - Roof / 1x10 cedar cut to 8 in width x 8 3/16 in slope length: 1 installed pieces Not quantified: - Screw geometry, texture, coating and sealant are omitted from CAD. ## Tools and equipment - Saw with rip guide and bevel adjustment - Drill, bits, countersink and screw driver - Tape measure, square, clamps and 3/4 in spacing gauge - Rasp or coarse scraper; eye, hearing and dust protection - Site-appropriate access and lifting equipment ## Instructions ### 1. Cut and mark the shell - Rip the 1x6 board to exactly 5 in and the 1x8 board to exactly 6 1/2 in. Actual thickness must be 3/4 in. - Cut front,back and side blanks 37 1/2 in long. Mark the dimensions on the cut layout from one common lower-end datum; cut the roof slope 11.31 degrees. - Cut four 1 1/2 in square spacers from 3/4 in offcuts. Cut the roof 8 in across and 8 3/16 in along the slope; bevel the short ends 11.31 degrees so they stand vertical. Check: The dry-fitted shell is 6 1/2 in square outside and 5 in square inside. ![Dimensioned cut layout for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-layout/layout.png?brand=1) Dimensioned layout; not a full-size cutting template. ### 2. Prepare the untreated post - Use one continuous 18 ft untreated naturally durable post, actual 3 1/2 in square. Obtain the site support design before buying or raising it. - Trim its upper end to 214 in at the high edge and 213 5/16 in at the low edge, measured from its bottom. Keep the same 11.31 degree fall as the roof. - Mark the future ground line 36 in above the bottom and the shell lower edge 180 in above the bottom. This puts the entrance 12 ft above the modeled ground. - Roughen all post faces within the shell and the landing area below it. Roughen the inside walls and remove splinters. Leave these surfaces untreated and unpainted. Check: Post top will sit 3 in below the matching underside of the roof over the post. ![Prepare the post for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-1/step-1.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ### 3. Locate the spacer blocks - Work with the post supported horizontally. Mark its front face 6 and 24 in above the shell lower edge; mark its rear face 10 and 28 in above that edge. - Set each spacer with its lower edge at the mark, centered across the 3 1/2 in post face. Hold blocks with clamps or a small spot of exterior wood glue while laying out the shell. - Keep each block 1 1/2 in wide, leaving 1 in of clear post face on either side so bats can pass the blocks. Check: Four blocks provide exact 3/4 in spacing; front and rear attachment heights are staggered. ![Fit the spacer blocks for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-2/step-2.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ### 4. Fasten the front and back - Set the front and back between the future side panels with their lower ends at the post mark. Match the low front and high back roof edges. - At the center of each spacer, drill a clearance hole through the wall and spacer. Pilot the post to the lag manufacturer's specification. - Install one 1/4 x3 in lag screw and washer through each block, four total. Tighten snugly without crushing the 3/4 in spacing. Check: Walls stay parallel; each lag reaches 1 1/2 in into solid post and no tip enters a roost space. ![Attach front and back for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-3/step-3.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ### 5. Attach the side walls - Seal the long edges of the front and back. Fit the side panels outside those edges, aligning lower ends and roof slopes. - Predrill through the side into the front/back edges. Fasten with 1 5/8 in screws every 6 in, starting 1 in from each end; keep centers 3/8 in from the side edges. - Check the four open lower gaps with a 3/4 in gauge. Keep the bottom open and remove sealant squeeze-out. Check: Each roost gap measures 3/4 in except where a spacer occupies it. ![Close the two sides for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-4/step-4.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ### 6. Fit the sloped roof - Center the roof with 3/4 in horizontal overhang on all sides. Its underside follows the wall tops at 11.31 degrees. - Seal the wall tops. Predrill and use four 1 3/4 in screws through the roof into wall edges, one over each wall. - Cover the roof with formed flashing and drip edges. Seal its fasteners and the upper seams; keep the entrance and bypass spaces open. - Prime and finish the exterior using water-based products and a shade appropriate to local summer temperatures. Allow the finish to cure; leave all roosting faces bare. Check: Roof fits continuously along all four sloped tops and sheds water away from the openings. ![Fit the sloped roof for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-5/step-5.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ### 7. Set the post and monitor the house - Use a site-approved support and raising method for the 18 ft post, local wind, soil and frost conditions. The model shows 36 in burial only; it is not a footing design. Keep the complete post untreated rather than applying preservative near bat-accessible surfaces. - Set the house with at least 12 ft of unobstructed air below the entrance and no nearby branches or predator access. Recheck clearance if the support design changes ground level or embedment. - Confirm the post is plumb and secure before removing temporary support. Inspect groundline condition and anchors periodically; replace deteriorated components only when the roost is unoccupied. Check: Mounting support has been checked for this site, and every entrance and roost passage remains clear. ![Fit the sloped roof for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-5/step-5.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ## Drawings and views ![Dimensioned cut layout for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-layout/layout.png?brand=1) Dimensioned layout; not a full-size cutting template. ![Prepare the post for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-1/step-1.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ![Fit the spacer blocks for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-2/step-2.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ![Attach front and back for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-3/step-3.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ![Close the two sides for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-4/step-4.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ![Fit the sloped roof for Post bat house](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-step-5/step-5.png?brand=1) Measured CAD geometry. Current parts orange; prior parts gray; future parts absent. ![Post bat house upper roost enclosure and post.](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-gallery-hero/hero.jpg?brand=1) Upper roost enclosure and post. The full above-ground post appears in the second view. ![Post bat house full post assembly above ground.](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-gallery-angle/angle.jpg?brand=1) Full above-ground post assembly. Below-ground CAD geometry is concealed by the studio ground plane. ![Post bat house lower entrance and spacer detail.](https://diyplans.org/media/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/image-gallery-detail/detail.jpg?brand=1) The open roost entrance around the post, viewed from below. ## Downloads - [Editable FreeCAD model](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/download-native/post-bat-house-post-bat-house-r1-model.FCStd): FCStd, 42285 bytes, file revision 1. Editable FreeCAD model matching this configuration. SHA-256: 3ada2b698f54f9f837f31a35187a266b139084550cbe6eaf26100e5680b457b2 - [Shopping list](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/download-shopping-list/post-bat-house-post-bat-house-r1-shopping-list.csv): CSV, 1941 bytes, file revision 1. Shopping list matching this configuration. SHA-256: af8ea961e70c3a468d3d00797153d306512ee11ba739ddf481816d336b531d0c - [Cut list](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/download-cut-list/post-bat-house-post-bat-house-r1-cut-list.csv): CSV, 526 bytes, file revision 1. Cut list matching this configuration. SHA-256: b9399cd380ebf18add865c139caa4135b1bb4b6ef942eeef721e984421f8006e - [CAD and materials package](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/download-package/post-bat-house-post-bat-house-r1-package.zip): ZIP, 134822 bytes, file revision 1. The sanitized CAD models, Blender scene, shopping list and cut list. Read the instructions and drawings on this page. SHA-256: 2c7cb6c2ff5c2857fd25afbb6753ec698c98871110818a5aa43a346d3c8d3323 - [Blender scene](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/download-blender-gallery/post-bat-house-post-bat-house-r1-scene.blend): BLEND, 339272 bytes, file revision 1. Editable assembly meshes, simple materials, three cameras and studio lights. The gallery images show the separately rendered wood finish. SHA-256: b06a4e95e9fde9a410a1b9e16aa8e7a6808866d5602c088291cb6d3e3350526d - [STEP model](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/cad-step/post-bat-house-post-bat-house-r1-model.step): STEP, 60758 bytes, file revision 1. Precise solid geometry for CAD exchange. Feature history remains in the FreeCAD file. SHA-256: de03358c690078e41323036c409b5b207101112d0e0f4097658aaccfbe52af76 - [IGES model](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/cad-iges/post-bat-house-post-bat-house-r1-model.iges): IGES, 121905 bytes, file revision 1. Surface geometry for older CAD tools. Use STEP when supported. SHA-256: b2618d31bc51b2eadeec32805f9cc48bfea3963a59900450f94f517b202594d2 - [STL mesh](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/cad-stl/post-bat-house-post-bat-house-r1-model.stl): STL, 6084 bytes, file revision 1. Triangulated assembly at full size in millimeters. Scale and prepare parts before 3D printing. SHA-256: ce8fc6852fa45a3fa1e3c156ba77c838a6f44b1a351ba87a302846c212934e28 - [OBJ mesh](https://diyplans.org/downloads/packages/58076ae5ad8d4435993ddf19d78d1120558f8e1a6cdc5fd8f967b6ae893b461d/cad-obj/post-bat-house-post-bat-house-r1-model.obj): OBJ, 5219 bytes, file revision 1. Triangulated geometry for modeling and rendering tools. Import using millimeters. SHA-256: 827b442252210ce2f1c55353a39dcdd2f9848abc9ff308ba3e01c491f91dc9b2 ## Using the CAD files - Open model.FCStd in FreeCAD. Box dimensions and editable constrained sketch profiles define the individual timber parts. - Use model.step for exchange; units are millimeters. Check the cut list before changing any dimensions. - Changing CAD dimensions does not automatically rewrite the instructions or purchasing records; revise all matching artifacts together. ## Sources Functional dimensions informed by the cited Washington Department of Fish and Wildlife woodworking sheet. CAD, instructions, schedules and illustrations authored for DIY Plans. - [WDFW Post Bat House](https://wdfw.wa.gov/sites/default/files/2019-11/post_bat_house.pdf) - [Bat Conservation International current bat-house guidelines](https://www.batcon.org/about-bats/bat-house-guidelines/)