Your observation house is plain wood cut sanded and glued, no paint, varnish or oils have been used on the wood.  The screen is made of nylon.  

Clean wooden toys by wiping with a dry cloth first. If a damp cloth is needed to remove dirt, moisten the cloth just to clean. Wipe away moisture and let air dry.  

Water is wood's worst enemy.  Don't let the observation house sit in water.  If it gets wet, dry it with a dry towel and let air dry.    The mesh screen has been attached and reinforced to make it strong.  With normal use it should stay attached for years.  The mesh may stretch if pressure is placed on the screen.  This will not affect the use of the observation house.  

Sharp objects will put holes or tears in the screen.    

If the wooden doors get wet, the wood may expand around the screws making it difficult to open.  The stiffness will reduce as the wood dries.  

If you do have a problem with the observation house, let me know through Etsy Conversation and I will see if I can help.