Deck question

Hi
I am in the process of building a storage platform under my deck. My deck is 12' depth (attached to foundation wall on one side) and 14' feet wide. The deck is about 5' above the ground level. The storage platform will be 8' deep (leaving about 4 ' to the foundation wall) and 14' wide.
A rudimentary drawing looks like
___Foundation Wall____________ | | 4' |____________________________| | | 12' | Storage | | Platform | 8' | | |____________________________| 14'
To build the storage platform:
A. Put 4x4 pressure treated lumber (rated for ground contact/use - ACQ 0.40 pcf) running perpendicular to the foundation wall to act as beams for the platform. Each of these 4x4 will be 8' long and with a distance of 2' from one beam to the next,
___Foundation Wall____________ | | 4' |____________________________| | | | | | | 4x4 | | | | | .... | 8' | 2' | 2' | | |____ |_____|_________________ | 14' Lawn side P
B. Install pressure treated lumber decking boards (5/4" x 6" x 14') across top of the 4x4 beams, so that each decking board will sit on all the 4x4 beams across the width of the platform.
C. Make the storage platform area "water proof" by installing corrugated PVC panels below the deck. These panels will be installed at a slant, with the highest point of each panel being near to the foundation wall and be 2" lower on the other end (Lawn side P in diagram above). This will cause any water that falls from above the deck to run out through the channels in the corrugated PVC out onto the lawn. I can even install a rain gutter at the end to cleanly channel this water out.
D. Use privacy lattice on 3 sides. Install a door made of pressure treated lumber on one side.
My questions are to do what can be done to make this area bug/insect/ animal proof? Thoughts I have had are following:
1. Install thick landscape fabric or 0.6 mil plastic sheet on the ground below the 4x4 lumber beams. Will these help to prevent bugs coming up the ground into the storage area? Given the PVC roof above the platform that will prevent the water from falling onto the storage platform area, will there be advantages to using the landscape fabric v/s the plastic sheet? Are there any advantages or disadvantages of the fabric or the plastic sheet?
2. Will attaching window screening to the privacy lattice and door to prevent bugs and insects from coming outside into the storage area.
3. Any other advice on whether the above plan will work or not? Any modifications that will help address any problems you see?
Thanks bob
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On Sep 10, 7:51 am, snipped-for-privacy@yahoo.com wrote:

Sounds like you have a pretty goodi plan for your storage area.
I think making it completely bug proof is going to be difficult. The screening on the inside of the lattice will be a good thing. Bugs are looking for moisture , food & protected area to lay eggs. As much as you allow or prevent these conditions or deny access will determine your success.
One thing I didn't understand, how are the ends of the 4x4's supported?
Also 4x4's are not the best choice for beams, I would suggest 2x6's or 2x8's depending on how much weight you're planning on storing.
cheers Bob
The plastic on the soil will get the area drier by preventing moisture from coming up out of the ground.
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Thanks Bob for your speedy response. I provide additional information and ask some new questions below.

Will I have a problem here with the PVC corrugated roof under the deck? Rationale, i expect that even though the PVC corrugated roof will channel the water falling through the deck above, it will probably retain some level of moisture & heat between the panel and the deck floor 5-6" above near the foundation wall and 7-8" on the Lawn side. Will this be an issue and if so, anything that can be done to alleviate this?
Are there any sprays etc I can use in the storage platform area overall to minimize the issue?
Also which will better to use a) lattice with 3/4" diamond/square shaped holes OR b) lattice with larger openings (1 3/4' or 2 1/4") ? The 3/4" opening lattice may not let larger bugs/animals get in. The larger opening lattice will let more air flow through. Or does using a window screen make the lattice a non issue.

The 8' 4x4 beams will lay horizontally on the ground going 8' from Lawn Side P in the figure above towards the foundation wall with 2' feet distance between the adjacent parallel beams. On Lawn Side P, I was going to take 14' pressure treated 2x4 lumber, set it on its side so that the 1.5" face is toward the ground and the 3.5" face is against the end of each 4x4 and screw it into the end of several 4x4s. The other side of the 14' 2x4 would be against three 6x6 vertical posts that currently support the deck above.
On the foundation wall side of the 4x4s, I was not planning on have any lumber attached to ends of the 4x4 but was thinking of just folding the landscape fabric/plastic sheet from the bottom of the 4x4 over its end to the top of the 4x4. On the top of the 4x4, I will have pressure treated 5/4"x6"x14' deck board lumber screwed into the top of each 4x4 beam. Each deck board will have 2 screws for each 4x4 beam. I was going to have 8 4x4 beams in the 14' width. So a 14' deck board will have 16 screws holding it to the top of the 4x4 beams.

I was mainly going to be using this for my kids stuff (e.g. a bicycles, scooters etc) and my lawn equipment (e.g. mower, edger, partial bags of potting soil, cow manure etc).

Thanks Bob
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clipped

live. Why not just build a shed?
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