http://www.unrealsoftware.de/forum_answer.php?post=348133

coordinates = {
    barr = {
        building_type = 1,
        x = {4,2,1,3},
        y = {-1,3,-4,1}
    }
}

add_building("turrets", 8, 1, 1)
add_building("turrets", 8, -1, 1)
add_building("turrets", 8, 1, -1)
add_building("turrets", 8, -1, -1)

add_building("gates", 6, -1, 0)
add_building("gates", 6, 1, 0)
add_building("gates", 6, 0, 1)
add_building("gates", 6, 0, -1)

function add_building(name, buildType, x, y) --preset name, building ID, x and y offset (tiles)
    local buildType, x, y = tonumber(buildType), tonumber(x), tonumber(y)

    if not coordinates[name] then --create a table inside if doesn't exist
        coordinates[name] = {}
        coordinates[name].building_type = buildType
        coordinates[name].x = {}
        coordinates[name].y = {}
    end

    if coordinates[name].building_type ~= buildType then --only 1 type of buildings per table allowed
        print("©255000000Error! Failed to add building type: \""..buildType.."\" to the existing type: "..coordinates[name].building_type)
        return false
    end

    --insert the given coordinates to the table
    coordinates[name].x[ #coordinates[name].x + 1 ] = x
    coordinates[name].y[ #coordinates[name].y + 1 ] = y
end

-- Is only used if you decide to build JUST ONE BUILDING, MANUALLY
function build_it(number, id, name, team) --player ID, name of the table to build, choose team of the object to spawn
    local number, id = tonumber(number), tonumber(id)
    if not coordinates[name] then
        print("©255000000Error! Table coordinates["..name.."] doesn't exist! [build_it]")
        return false
    end

    local TileX = coordinates[name].x[number] + player(id,"tilex")
    local TileY = coordinates[name].y[number] + player(id,"tiley")
    local buildingID = coordinates[name].building_type

    if not team then --if the team isn't given, take player's team
        team = player(id, "team")
    end

    if not entity(TileX, TileY, "exists") then
        parse("spawnobject "..buildingID.." "..TileX.." "..TileY.." 0 0 "..team.." "..id)
    end
end

function build_all(id, name, team)
    if not coordinates[name] then
        print("©255000000Error! Table coordinates["..name.."] doesn't exist! [build_all]")
        return false
    end

    for k,v in pairs(coordinates[name].x) do --FOR EVERY ENTRY in table BUILD THE BUILDING
        build_it(k, id, name, team) -- k is the key
    end
end