begreen living on the coast is like having a big mass heater already - the ocean. The ocean keeps the temps from getting too cold or too hot. I grew up on the Southern Oregon coast - my parents just used a few small wall heaters. It would snow every 3 or 4 years. Where I live now the temp spends 3 or 4 months in that 10 to 35 F range.
For anyone considering a masonry heater, I would start looking around for materials. You must start with the inner materials first - that is fire brick. I look on FB marketplace and find some sources of fire brick. Prices range from $1/brick up to $5/brick (and higher). One must study the brick - don't buy pumice type bricks - these are a no-go for a mass heater. But most firebrick are going to work fine. It is overkill for just burning wood. Light, medium, or heavy duty brick will all work.
I've narrowed my brick choices to these 3 in my area, $1 brick -
https://www.facebook.com/marketplace/item/466542649097329/?ref=search&referral_code=null&referral_story_type=post&tracking=browse_serp:57349aa0-e0fd-4bcb-9798-39f567d426d3
$2 brick -
https://www.facebook.com/marketplace/item/424174999988695/?ref=search&referral_code=null&referral_story_type=post&tracking=browse_serp:57349aa0-e0fd-4bcb-9798-39f567d426d
and $3 brick,
https://www.facebook.com/marketplace/item/1881300572290863/?ref=search&referral_code=null&referral_story_type=post&tracking=browse_serp:57349aa0-e0fd-4bcb-9798-39f567d426d3
Which to choose? I would go with that $2 brick. It is from PA (best brick state) and appears to be well made. It is probably a medium duty brick. And they look to be in good shape. The $1 brick is probably okay, too, but is more worn. The $3 brick looks to be new. Why not this brick? It is new out west. I'm guessing this brick is from California - it is inferior to the PA brick, and it will crumble easier - but it would work, too. My order of preference - $2 brick, $1 brick, and $3 brick. How much should I buy?
You are probably going to need over 1 pallet, but less than 2 pallets. See if the seller has a partial pallet or just buy 2 pallets. Now we need the hardware like a door, oven door, and cleanouts. I would try that company in Oregon for these parts @
https://www.firespeaking.com/product-category/masonry-heater-hardware/. But there are other companies, too. Remember a small door works fine even on a big heater. Now we need to figure out what we are going to use for the visible 4-to-5-inch outer layer.
Many things will work - river rock from your creek, no-nonsense concrete pavers, flagstone, engineered puzzle-piece stone, stucco, old common bricks, etc...... Find what you prefer. Buy some plans from the Masonry Heater Association @
https://www.mha-net.org/, and ask a mason or two if you could volunteer on a build. They will be thrilled - they will treat you like a mule hauling all of the heavy stuff and mixing the mud, too. Or go to a workshop/gathering. Ask questions. Of course, a masonry heater is best for new construction (in the right climate) because they weigh so much. Don't sweat it, you just need to reinforce the floor where the MH will be sitting.
