Bat House Forum

[Georgiabat]

I am building 2 bat houses, estimated weight 90 pounds. I have 2 2x4s 16 feet long that I am going to screw together then drop into a hole 3 feet deep with 100 pounds of cement. I am going to make a h-frame with 2 2x4s 6 feet long and connect it to the top of the 16 footers. So 16 feet minus 3 feet of ground lose = 13, adding the h-frame gives me 2 more feet to get the recommended 15 feet. Will the 2x4s in this configuration handle the weight of 90 pounds? Any info is appreciated .


2 houses- 1 by 3 feet tall, 4 chambers, Marietta, GA

[JR0835]

You wrote "I have 2 2x4s 16 feet long". If that is all you have for posts, the answer is no, it will not work. It will not support the two bat houses. If, however, you have four 2 x 4's screwed together to make two posts, it will work fine. I am a design engineer.

[JR0835]

If you will only have one post consisting of two 2 x 4's fastened to gether to make a 4 x 4 (actually 3 1/2" x 3") , it will support the two bat houses if the wind never blows. Your main problem is not the weight of the houses, but the bending moments caused by winds. If you only have the one post, then fasten the two 2 x 4's together in a "T" shape with lots of wood glue. The glue is very important. Use exterior glue plus screws. This will give you a post that is 3 1/2" x 5" overall. Then, install the post with the 5" axis in the direction of the prevailing wind in your area. Then 3' in the ground is okay. This should work until a hurricane comes along.

[Georgiabat]

Will combining 3(instead of 2) 2x4s 16 feet long with wood glue and screws make the post stronger or not?

[Georgiabat]

I understand you now, combine 4 total 2x4s to make it strong enough to handle the weight and wind.

[JR0835]

Four 2 x 4's are not necessary. Use three and fasten them in the shape of an "H". That's all you need.

[Terry Lobdell]

I never skimp on material for a bat house post.......based on much experience the stiffest posts are hollow.......you could sandwich two 2x6's around two 2x4's........