Crawlspace Vents

[buckeye]

A bank appraiser came to look at our house today as part of the loan process for the buyers purchasing our house. He said the house was fine, but the only problem was that he felt it did not have enough crawlspace vents. When I first moved into our house, I thought the same thing (I guess our bank did not), and considered putting some in myself. However, the crawlspace is pretty dry and I felt it was some risk to break through the foundation wall and the exterior brick to put in a few more vents. I guess I questioned the need to vent and already dry space that would not help much more, especially if they cracked brick or foundation walls.

In your all's experience, how hard would it be to install a new vent through block walls and exterior brick? I'm thinking this is something I should let a professional do. Any ideas on how much it could cost? I'm hoping that the bank will let it go since the certified home inspector said the crawlspace and foundation was great. I'm just wanting to get some ideas in case it goes the other way. Thanks in advance for any input you may have.

 

[StoneHeartFarm]

buckeye,

Crawlspace venting is an arguable point. Do you have any vents at all? Check your local code and see what it requires (usually a % of floor size). This may or may not be enough to get your bank to involve itself (ie make you add vents). A lot depends on the bank and the "estimated cost to cure". If the appraiser does not make a big deal about it, it may pass right through the bank without another word. (After all, they made a loan on it once.) Some banks won't care and others will throw hissy fits. Did the appraised value come out high enough to clear the loan?

Usually, even if the bank does say "Hey, wait a minute", you should still have a chance to appeal (get a second opinion, etc.)

In the meantime, adding a vent through the block would probably be fairly easy. I'm not so sure about the brick. I did see masonry blades (both wet and dry) at Home Depot that will fit your skillsaw. That would probably get you through the brick.
SHF

 

[ric]

I live just North of Columbus in Delaware County. My house was built in 1975 "to code", which included the crawl space under the house. This is a very large one story house on the top of a hill. The yard was graded with minimal slope right up to the foundation. The correct number of crawl space vents were installed. I have a septic system and a 25,000 gallon cistern, no well and no county water. In 1994 all the floor underlayment, all the floor joists, all the plumbing, all the electric, all the carpet was replaced when the joists and floor rotted out despite being "to code". Seems like you can't have too many air vents especially when it gets rainy and stays wet. You know when there's a problem the sudden mold and mildew smell will knock you down one day then go away then return right after it rains hard. $40,000 later I now have a 40 x 80 14 block basement with excellent drainage and new furnace and A/C and a new mud room over the hole for the stairs that was where the bobcat burrowed under the house to dig out the mess. Wish my banker had taken an interest in the number of crawl space vents when the house was built, my architect, builder and contractor didn't. Looking at my house today you can't tell there was a problem except when you see pictures of my house with me in them I am always standing as I can no longer sit down because my butt is still too sore. If I had only known. BTW, if you have crawl spaces and I'll assume these are open areas covered with gravel under the floors in your home be sure the floor joists in the crawl space are covered with insulation and plastic. The more the temperature stays stable the less likely condensation will form on the wood. Another thing to consider if you have not already done so is to cover the gravel in the crawl space with two layers of .6mill plastic then cover it with gravel or insualtion. Good luck, the point where preparation and opportunity meet, ric

 

[patrickg]

Buckeye,
With crawl space vents, more is usually better, especially if placed properly. I installed automatic open/close vents in my mom's new house. Unfortunately a lack of comms between boss and workmen resulted in their not forming up for vents at either end of the house just the long sides. Had to use a hammer drill to make holes in the 8 inch thick stem walls. No disaster, some slight cosmetic grouting required as the flange of a vent did not cover the edge of a hole. Diamond saw would have been neater but hammer drill is what was used (available).
The vents I used came from Lowes and are mostly plastic with some metal screening and a coil spring that opens and closes the louvers automatically at preset temps. They open when it warms up and close when it cools down. Work fine so far and the mechanism is dead simple and should last. They were a bit under $10 each. Simple and easy to install about 10-15 seconds each.
Not to be a bad guy but... Did you use a hygrometer (humidity measurer) to make your determination regarding how dry it is under the house? Radon reduction is a side benefit of good venting. Around here it is common to vent dryers under the house and to use pretty minimal under house venting. I insisted on an outside dryer vent and put in sufficient crawl space vents. I'm gaining a reputation as a fanatic because I engineer solutions rather than just do what has been done. I never cease to be amazed that when you point out an error in practice rather than being thanked you are appraised of the number of years or decades the person/company has ben doing it that way. Stating that you have been doing something wrong for a long time seems to be a poor defense to me but after all I'm a fanatic. Isn't this like the guy who claims he will live forever and offers as proof that it is working perfectly so far?

Patrick

 

[RPM]

I'll second patrickg's comments on getting a hygrometer and checking the humidity for yourself first. Always smart to have some statistics to hand when trying to argue against a home inspector's brainwave. They may still argue that the measurements you are taking today don't carry any weight as the humidity will vary throughout the course of the year (may be fine now but not in the Summer).

I'll bet that you will need a hammer drill and a good long masonry bit to get through the block and brick. You may be able to use a cutting wheel on a chop saw or angle grinder to tidy things up and avoid some cracking on the inside and outside - but there won't be enough working room to use it for the full thickness of the cut. I haven't put in vents to the exterior - but did put in vents between 2 enclosed crawl-spaces and the main basement on my last house (big fixer-upper).

When drilling, make sure the holes you drill are close together so you don't need to pound the wall into submission to chop out the vent hole when you're done. The real buggers are the holes you need to drill through the full thickness of the block (not through the void). Be patient and try and keep the drill as level as possible for these. It's better than trying to chop through with a chisel and remove the whole block by accident.

The best tool I've seen for handling these jobs is an abrasive water jet cutter - but they don't make them in homeowner size!!

Patrick

 

[Egon]

Cutting a hole in masonary/concrete

There are industrial circular diamond tipped water cooled hole saws. I am not sure what the maximum diameter may be but have seen a 12" cut through 10 " of concrete and rebar. Took about 15 minutes of cutting time.

Egon

 

[heehaw]

a fairly new recommendation in this area, put in the required number of vents, then seal them, put down 6mil plastic and insulate the walls of the crawlspace. unless of course you have ground water under your house..
when we built our house in 86, i raked the ground to remove the rocks, put down 6mil plastic and then covered it with sand; until @6 weeks ago when we had a 7 inch rain, i had never had any moisture under the house, i could work under the house, and then just a slight brushing and my cloths were clean..
heehaw