Thin like regular cedar boards. I am going to add some foam insulation inside and add another layer of thin wood to hold in the heat a bit better. May find a dog door for the front of the size is generic enough. Had the front trim fall off recently which annoys me, but can be easily fixed. The big baby is under a covered patio so he’s not really in the weather and it’s holding up fine. And it’s a perfect fit between the shrimp and air condenser so it’s just what we needed. Def not big enough for a dog bigger than ours at this size. Our Dante is smaller standard size bully and he just fits! Not cut out for larger breeds.