Replacing 2x6 deck boards with composite

[Banjomaniac]

I want to rip off all the 2 x 6 treated deck boards and replace them with thinner composite boards that are 1/2 inch thinner, my question is should I shim the half inch difference in the thickness of the boards with something that is weather resistant and I didn't see anything 1/2 inch thick at Lowes. Where it meets the house under the vinyl siding there's a gap, would it really make a difference or is it just esthetics? This is what it looks like with a few boards slid in place.

 

[Silentrunning]

Welcome to the forum Banjo. Thank you for a complete and thorough explanation of your question. If the gap really bothers you then go to the big home improvement store and get a quart of paint that matches the siding. Once all the boards are removed paint the area under the siding. Put the new boards directly on the joists. The only place that will look funny is where you can see that the vinyl siding is cut out for clearance on the old boards. Put a flower pot in front of the short vertical section and you will have a professional looking job. Good luck.