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Old 01-14-2009, 10:09 AM   #1
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Foundation crawl space vent size problem


My new (to me... 5 years old) house is in a flood zone in SC. Apparently, to receive a discount (around 50%!) on my flood insurance, I need as many square inches of crawlspace vent area as I have crawlspace square footage, which is around 2050ft^2.

My elevation inspector came and determined that I only have 1250in^2 of vent space because of the foundation vent covers that are used. I have 20, of the standard 16" x 8" or so vents.

Anyway, according to my calculations, I need to find vent covers that will get me at least 103in^2 of open area to satisfy my requirement and reduce my insurance premiums... anybody have any idea where I can get such a vent? The best I can find on google is 82in^2.

Is it difficult to replace these vents?

If I have to add more vents, can I just hammer drill out some more holes anywhere in the cinderblock and brick to add more vents? Are there structural issues with this?

Thanks.

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Old 01-14-2009, 12:45 PM   #2
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Foundation crawl space vent size problem


check if you can use powered vents. This will increase the air flow. And yes it is somewhat easy to add more.

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Old 01-14-2009, 12:51 PM   #3
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Foundation crawl space vent size problem


Thanks for the comment.

I dont have any reason to think powered vents would not be allowed. Although... the whole point of concern is for flood waters to pass through the crawlspace effectively though, so maybe they wouldnt allow them. Its not that there is not enough airflow... I guess they think if theres a flood, my house would wash away.

Thanks,
Eric
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Old 01-14-2009, 01:13 PM   #4
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Foundation crawl space vent size problem


Quote:
If I have to add more vents, can I just hammer drill out some more holes anywhere in the cinderblock and brick to add more vents? Are there structural issues with this?
Is it difficult to replace these vents?
Ayuh,... It's your Foundation,... Of Course there are Structual Issues involved...

The Degree of Difficulty is only revelant to what Your abilities are,...
I'd call it Pretty Easy,... You might think it's Impossible,.. Donno...

I know the basis of your question is Flood Mitagation,... Not Ventilation...
Would it be possible to twin the vents you have Now, as in above or below the present vents,...
That'll lessen the Structual part of the equation, as the foundation is already cut out there...

I've got a couple of places in the Flood zone,...
1 of them is going Up 12', instead of the required 4' to get out of the flood plain,...
It'll tie into the terrain better, up higher,+ the expence isn't much more...
It'll all be set on a structual Steel foundation once it's Up there....

Good Luck,...
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Old 01-14-2009, 01:37 PM   #5
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Foundation crawl space vent size problem


I don't know if placing "double" vents on top of each other will work because they have to be a certain distance from the ground (12" I think). Maybe I could find a couple high enough to put another vent under it.

How would I find out where in my foundation I could cut another hole? It this something I would have to get an engineer/contractor to check out, or is just spacing the extra couple of vents evenly between the others enough?

I feel pretty comfortable doing most medium to large DIY projects myself... I just get iffy whey it comes to potential structural changes to my new house.

Of course, all this is unnecessary if I could find some reasonable looking vent covers that only restrict 25 of the 128 square inches of vent area already in place... the guy actually told me I could take the covers out and pass, it would just look like crap.

Thanks for the input,
Eric
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Old 01-14-2009, 01:56 PM   #6
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Foundation crawl space vent size problem


any new vent will require that you also add a 2" X 4" steel lintel over the opening. This will allow you to make this without structure degradation. The lintel needs to overlap the vent opening by at least 1/4 the opening made.
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Old 01-14-2009, 02:08 PM   #7
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any new vent will require that you also add a 2" X 4" steel lintel over the opening. This will allow you to make this without structure degradation. The lintel needs to overlap the vent opening by at least 1/4 the opening made.
OK, this is getting a little more complicated. Where can you get these lintel's? So I would have to chip out an extra 4" (16" opening) at the top of the opening wide enough to insert the lentel, then cement it back in?

If Im hearing you correctly, I need a "T" shaped opening, where the virticle cut is wide enough for the vent cover, and the horizontal cut is about 2" thick, and onl y about 4" deep into the cinder block?

Thanks alot... seems that there may be more involved than I thought... but Im not giving up

-Eric
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Old 01-14-2009, 02:27 PM   #8
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Foundation crawl space vent size problem


yes notch the top to slide the steel into place. Use a 14" diamond saw and a good hammer drill. Drill holes all the way though in a line then chisel out the slot. See easy! Buy the lintels at your local masonry supply store.
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Old 01-14-2009, 02:40 PM   #9
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Thanks... thats what I needed.

One more quick question... does the lintel need to be sealed in with concrete or anything? seems to me, if the notch on top is wide enough for the lentel to slip in, it wouldnt actually be supporting anything until the wall started to sag.

Thanks,
eric
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Old 01-14-2009, 02:44 PM   #10
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Foundation crawl space vent size problem


you could just cut in the 4" flange tight and let the other half lap the top inside edge. But yes you want it to support the weight above. You will need to fill with anchoring cement (epoxy cement)
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Old 01-14-2009, 02:49 PM   #11
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Foundation crawl space vent size problem


Twenty vents seem to be a hell of a lot of vents,Ive wired some big square footage homes before without nearly that many vents. They dont help the structures foundation
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Old 01-14-2009, 03:01 PM   #12
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Twenty vents seem to be a hell of a lot of vents,Ive wired some big square footage homes before without nearly that many vents. They dont help the structures foundation
But this is not just a house, it is a boat in waiting.
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Old 01-14-2009, 03:08 PM   #13
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Foundation crawl space vent size problem


Bob, thanks for the advice and quick responces... I think I have a good idea of whats required now

Quote:
Originally Posted by drdon51 View Post
Twenty vents seem to be a hell of a lot of vents, Ive wired some big square footage homes before without nearly that many vents. They dont help the structures foundation
I figured it should be plenty too... as mentioned before, the fact that it is in a flood zone is causeing the problem. Accourding to my inspector though, if the current vent covers are used 32 vents will be required for this 2050 square foot house... thats why my main concern is to find better vent covers.

Of course, like Bob mentioned, I could just seal up all the vents, strap a couple outboards to the back deck rails and wait for the first flood to make us into the houseboat of our dreams.

Thanks,
Eric
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Old 01-14-2009, 04:58 PM   #14
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Foundation crawl space vent size problem


that is a smart way to start. Try these.
http://www.crawlspacedoors.com/pdf_d...EV%20%2707.pdf
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Old 01-15-2009, 10:00 AM   #15
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Originally Posted by Bob Mariani View Post
that is a smart way to start. Try these.
http://www.crawlspacedoors.com/pdf_d...EV%20%2707.pdf

Thanks for the tip... I called the fella who runs that site, and he was very helpful. it looks like his product could satisfy my needs... I might could even put a large vent over the intry door to get the rest of the square inches of area I need.

He also mentioned another product... smartvent... they have an "engineered" area similar to the above product, that is even larger than the actual LxW square inches (200 in^2 per vent). nice thing is, they will fit into my existing holes, unlike the above product... mad thing is they are like $200 each (and I need 7). anybody know of a similar, but less expensive product than the smartvents?

Thanks,
Eric

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