Dirt Basement & Crawl Space – Rotten Joists
Hey everyone
First post here on FHB. My wife and I recently bought a 1880 farm house in the highlands region of Maine(climate zone 6).
We located several rotten floor joists during the inspection and were able to negotiate a decent amount of money off the asking price so we proceeded with the purchase. We have a plan in place to sister all the joists and work on leveling up the floor but my major question relates to the moisture issue.
I should note the home has a dirt “full basement” plus two additional crawl spaces . The interior perimeter walls all have spray foam, just no floor coverings. The electric water heater is placed down in the main basement as well as a force hot air furnace.
We recently had a basement systems company give us a quote for their recommendation. This recommendation included six mill plastic encapsulation in the floors of two crawlspaces sealed up to the spray foam, a 3” slab foundation in the main basement portion, trenching the perimeter of the main basement, a 1/3hp sub pump and a dehumidifier. this quote rolled in at around $18,000. They claimed and showed on their software that the slab was actually $1000 less then doing the 6mill barrier in main basement. He also showed me his humidity monitor and observed 92% humidity in the main portion of our basement. There is no question this is an issue we must deal with.
I will also add we intend on replacing the hot water heater with a heat pump hot water heater to assist in efficiency as well as deal with some dehumidification.
although I believe the companies proposal would be the best solution, $18,000 seems like a lot of money to spend.
Do you folks think I would achieve a similar end goal if the put 6mil or greater down myself, brought down another dehumidifier along with the heat pump water heater? What could I use for tape to seal the plastic to the already existing spray foam? I realize these folks are professional at what they do just trying to weigh out all my options.
thanks!
Nick.
Replies
That proposal does not seem unreasonable for the amount of work involved. Doing it yourself you may be able to get 70% of the way there by spending a whole lot less but you probably wont get to the same 100% solution.
If you do a bunch of research and you are meticulous you could install the vapor barrier yourself. There are newer heat pumps as well as hot water heaters that will dehumidify as they run and they are pretty efficient. If you go the stand alone dehumidifier route get yourself a whole house ducted unit (even if you use it unducted) Aprilair or Honeywell make them and they are not cheap ($1000 +). I use one at home an I can suck a lot of moisture out of the basement.
Spray all of your joists before and after sistering with Boracare- it will protect against rot as well as termites and its easy to apply and relatively cheap insurance.
If there is good reason for the internal trench, you will want to take care of the flowing water one way or the other.
want to be careful about disturbing soil near the base of old basement walls.
Take a look at the company Stego. They sell a 15mill barrier as well as tape and termination bars their website has great installation instructions:
https://www.stegoindustries.com/hubfs/Installation/Stego-Wrap-Vapor-Barrier-Retarder-Detailed-Installation-Instructions.pdf
Appreciate the insight. It’s seeming more and more that it’s probably money well spent to have the work done by the professionals and leave me to “easier” remodeling jobs that buying an old farm house has brought me?
$18K seems pretty reasonable for that work.