In Genesis chapter 6 we find the building plans for the ark God instructed Noah to build. These details are not included just to add some interesting tidbits of information to the Bible. The building plans are written in parabolic language and contain spiritual truth that relates to the Gospel message.

We’ve learned that water is used in the Bible to sometimes point to the living water of the Gospel that brings salvation. At other times, it is used to signify judgment (see Word Study on "Water"). In the account of the Flood, the water is a symbol of judgment on mankind for his rebellion. In that day there were only eight people on the planet who were saved:
"Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water." (1 Peter 3:20)
As far as the historical parable is concerned, those eight people represent all of the true believers. We’ve learned that ships in the Bible typify the church (see Word Study on "Ship"). We have to examine the context to know if the ship in view is the eternal church made up of all the true believers or if it is the corporate church organization. In the case of this historical parable, the ark represents the eternal church because it contained only true believers who were spared from the wrath of God. This body of believers is also spoken of in the Bible as the body of Christ:
"So we, being many, are one body in Christ, and every one members one of another." (Romans 12:5)
"Now ye are the body of Christ, and members in particular." (1 Corinthians 12:27)

It is in Christ that the believers find their safety. Those who are in Christ are spared from the condemnation of God:
"There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit." (Romans 8:1)

Let’s consider some of the details of the ark’s construction. God instructed Noah to pitch the ark with pitch:
"Make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch it within and without with pitch." (Genesis 6:14)
The verb “pitch” in this verse is translated from the Hebrew word kaphar, which is found about 100 times in the Bible and is almost always translated as “make atonement.” The covering of the ark with pitch was a picture of the eternal church being covered by the redemptive blood of Christ. It is through the shedding of Christ’s blood that atonement was made for the believers:
"And almost all things are by the law purged with blood; and without shedding of blood is no remission." (Hebrews 9:22)

God instructed Noah to place a window in the ark and a door in the side of the ark:
"A window shalt thou make to the ark, and in a cubit shalt thou finish it above; and the door of the ark shalt thou set in the side thereof; with lower, second, and third stories shalt thou make it." (Genesis 6:16)
The Hebrew word from which “window” is translated in this verse is tsohar, which is found 23 times in the Bible and is typically used in connection with the brightest part of the day. The window in the ark signifies the source of light for the eternal church. That source of light is, of course, Christ:
"Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life." (John 8:12)

The door in the side of the ark also points to Christ:
"I am the door: by me if any man enter in, he shall be saved, and shall go in and out, and find pasture." (John 10:9)

Christ is the only way to enter into safety. Many people try to ensure their eternal safety through some other means than Christ, but they will all remain under the wrath of God:
"Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber." (John 10:1)
The door to salvation is currently open, but there will come a day when salvation will no longer be possible. The door will be shut just before God brings judgment on the unsaved. This is illustrated for us in this historical parable when God shuts the door to the ark, reserving everyone outside the ark for destruction:
"And they that went in, went in male and female of all flesh, as God had commanded him: and the LORD shut him in." (Genesis 7:16)

God gave Noah the exact dimensions for which to construct the ark:
"And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits." (Genesis 6:15)
The numbers mentioned here are 300, 50, and 30. The number 300 breaks down into 3 x 10 x 10. The number 50 is 5 x 10 and the number 30 is 3 x 10. Therefore, the significant numbers God is bringing into view are 3 (God’s purpose), 5 (atonement), and 10 (completeness). We’ve seen that these numbers have everything to do with Christ’s redemptive work and it therefore makes perfect sense that we find them so intimately related to dimensions of the ark.

God gave Noah very specific instructions on how the ark was to be constructed. Likewise, we are given the blueprint for salvation in the Bible. If we inject our own ideas and modify any aspect of God’s salvation plan to suit our desires or logic, then it no longer is a blueprint for salvation but becomes a blueprint for death:
"There is a way which seemeth right unto a man, but the end thereof are the ways of death." (Proverbs 14:12)