My world generation script will only generate grass can anybody help?

It only generates grass spires i dont see why it is not working

my script:

--Static variables
local prefabs = game.ServerStorage.Prefabs
local cubes = 90
local width = 10
local length = 10
local height = 5
local x = -0.5
local y = 1.5
local z = 1.5
local rows = 1
local w = 0
local l = 0
local h = 0
local chance = 0
math.randomseed(tick())

--Void
function DrawBlock(block, xp, yp, zp, location, num)
	if num == "" then
		local newBlock = prefabs[block]:Clone()
		newBlock.Parent = location
		newBlock.Size = Vector3.new(2,2,2)
		newBlock.CFrame = CFrame.new(xp,yp,zp)
	else
		local newBlock = prefabs[block]:Clone()
		newBlock.Parent = location
		newBlock.CFrame = CFrame.new(xp,yp,zp)
		newBlock.Size = Vector3.new(2,math.random(3,10),2)
	end
end

for i=1,width,1 do
	for i=1,length,1 do
		wait()
		if w==width then
			w=0
			rows=rows+1
			x=x-3
			z=1.5
			print(l)
			l=l+1
		elseif l == length and h ~= height then
			w=0
			l=0
			z=1.5
			y=y-3
			x=0.5
			for i=1,width,1 do
				for i=-1,length,1 do
					for i=1,height,1 do
						wait()
						if w==width then
							w=0
							rows=rows+1
							x=x-3
							z=1.5
							print(l)
							l=l+1
						elseif l == length then
							print(h)
							h=h+1
							w=0
							l=0
							x=1.5
							z=0.5
							y=y-3
						elseif h == height then
							break
						else
							chance = math.random(0,3)
							if chance < 1 and chance > 0.6 then
								DrawBlock("Copper",x,y,z, workspace.World, "")
							elseif chance < 1 and chance > 0.5 then
								DrawBlock("Stone",x,y,z, workspace.World, "")
							end
							w=w+1
							z=z+(-3)
						end
					end
				end
			end
			repeat wait() until h == height
			break
		else
			chance = math.random(0,3)
			if chance < 0.15 then
				DrawBlock("Grass",x,y,z, workspace.World, chance)
			elseif chance < 1 and chance > 0.5 then
				DrawBlock("Stone",x,y,z, workspace.World, chance)
			end
			w=w+1
			z=z+(-3)
		end
	end
end