Lyric discussion by pocketsfullofshells 

I think its about tying to make something out of flawed material, houses are often seen as symbols of relationships, especially in darnielle's work (see the house that sripped blood). So the fact that this couple are building their house out of quite obviously flawed material, shows that their relationship was doomed from the start, however, in line with true human nature, they are willing to try anyway. Ignorance is bliss

I like this interpretation. But, I would go further in saying that the reason why their relationship was flawed was because this girl wanted to be (or just was) shallow. He wanted to still be with her (she wanted money and he sold off most of what he owned) but couldn't be as shallow as her. After they die their hair, she stares into a void and loses the depth he saw in her from what they experienced together, i.e. scaling mountains beneath the surface and ringing out blood drenched bed sheets like he's trying to help her with demons...

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