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cody 03-20-2010 09:38 PM

Suggestions for diverting water away from air vent
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I am new here - hi everyone, looks like you've got a great little community of people helping each other. I'm from New Zealand, so our weather and typical construction methods may be a little unfamiliar but I'm sure you'll understand.

Basically, for several years we've had an issue with moisture entering one corner of the house. I have only just realized that it may be due to this air vent (pictured) in the concrete block base sitting at ground level.

Every other vent is raised above ground level, and this one is often clogged with leaves and debris as though rainwater has been flowing in here.

The lower set of holes in this grate look as though someone has at some point attempted to fill them up with cement or mortar, however they either did a poor job, or it has broken away over time.

To stop water flowing in here, I am considering either making a raised "lip" of mortar on the concrete in a semi circle around the opening, or perhaps just having a go with a silicone gun and filling all the gaps where the concrete and the vent meet, and probably sealing over the lower row of holes in the vent.

If you have any other suggestions for something that will be simpler, more effective and/or more durable then I would be very grateful.

Thanks very much.


travelover 03-21-2010 08:00 AM

I think that your idea of making a raised lip around the vent is a good one. The downside is that it may act a a catch basin for rain if you don't have protect it from above, somehow. What is on the other side of the vent?

Bud Cline 03-21-2010 01:25 PM

How many other vents are there? Cross flow ventilation is important to a crawl space but I am wondering why that troublemaker can't simply be filled in total with cement patch and abandoned completely.

I would also caulk the entire length of the crack along the structure.:)

Another picture of the entire area would be helpful maybe as opposed to the closeup..:)

cody 03-22-2010 05:49 AM

Thanks guys,

I think there are about 3 other vents - I might do a count and get another photo when I next get a chance.

The vent leads to the crawlspace under the house with a dirt floor. After heavy rain, the water somehow seeps upwards into the floor joists and (I'm pretty sure) into the wall cavity above, it also manages to trickle along two concrete block walls on the interior of the crawlspace.

Yes - looking at the crack along the structure I was thinking it would make a good channel for rainwater. :-)

Any sort of caulk you'd particularly recommend? We've got plenty of different types to choose from, I figured I'd just go to the hardware store and ask for some sort of silicone based exterior product.

I didn't think about the lip causing a basin effect. I could just make the lip very close to the vent. I am a bit unsure about sealing the vent completely as dampness is a bit of an issue in the basement in general, common in my local area.



travelover 03-22-2010 09:00 AM

You would do well to cover the dirt floor with a plastic sheet. Google "crawl space plastic" and you will find a wealth of information.

The dirt allows water to evaporate into the space and then re-condense onto the underside of the structure.

Bud Cline 03-22-2010 06:28 PM


You would do well to cover the dirt floor with a plastic sheet.
That would have been my next suggestion also.:)

cody 03-24-2010 06:18 PM

Thanks - the plastic is on my to-do list. :-)

Once I've confirmed this leak is sorted I'm planning to have some underfloor insulation installed, then I was going to do the plastic.

I figured better to get the insulation done first (currently we have none) so I don't have tradesmen tripping over the plastic and putting holes in it which I guess would sort of defeat the purpose. :-)

Bud Cline 03-24-2010 09:25 PM

Actually the insulation workmen would probably appreciate having the plastic there.

How about you buy the plastic and give it to the insulation workmen for their use while installing the insulation, then just tell them to leave it there when they are done.

If you have to re-do it, plastic is cheap and no harm done. If they don't wreck it - even better.:) he he he!:banana:

It'll be our little secret.

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