Land covering the earth

At present I beleive that Land covers about 25 percent of the Earth. I have heard how Dubai is making so many large artifiical islands, made out of natural materials, such as Palm Jumeriah, The World Islands, The Dubai Waterfront etc. I heard some of...

these manmade Islands are the size of the City of Paris, which are dramatically increasing Dubai's coastlines. This got me wondering as to how much of the Earth's surface can be theoretically covered with land using materials found on Earth? Does anybody know how much land we can build to cover the surface of the Earth? Like how much percent of the Earth can be covered by land by using resources on Earth and how much land can cover the Earth without severely disrupting the water supply and other natural cycles? Please give suggestions. Thank You.

I dont think it could ever get over 30, 35 %. Not sure if what I know about is Dubai, but I know that they have these huge ships with gigantic vacuums that suck up sand and they take it where they want and compact it and Walaa... A new island.