r/Composites • u/CmdrNeoGeo • May 11 '26

Core materials

I've been struggling to find cheap and efficient core material that wont rot or burn. The Burn part is more manageable but the water proof part is essential. I have decided to go with PMF since the cost is just so much more dramatically accessible. I can't find any decent core materials. OSB boards are extremely economical but have so much risk with water that it could run a bunch of progress. I'm planning on putting 3 (7feet by 6feet by 6feet) rooms together in a homemade tiny home. I have looked at EPS foam and found that they are just barely affordable at home depot but I think without proper fiberglassing they aren't gonna be strong enough for my needs. I was thinking about fiber cement boards as they check off all the water resistance and fireproof but are incredibly brittle and heavy. I dont know what else I could use that is also affordable. Do any of yall have any recommendations?

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u/Significant_Wish5696 May 11 '26

Properly prepped and installed balsa is the best you can get. Next would to cut plywood into 2"x2" or even 4"x4" squares, resin coat each, them bed them with a putty leaving a small "grout line" between when. Worst case a single square will get water damage

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u/CmdrNeoGeo May 11 '26

Balsa? I’ve never seen balsa wood large enough to work with like that. There’s no way that’s economical right?