Replies

1. 
   rez | Jul 26, 2007 07:20pm | #1

   Greetings Tim,

   This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.

   Perhaps it will catch someone's attention that can help you with advice.

   Cheers

    

    

2. 
   Ragnar17 | Jul 27, 2007 08:03pm | #2

   I would like to box in the crawl space to keep cold air out.

   Hopefully, someone with more knowledge than myself on this issue will chime in.  However, it sounds like what you're proposing is not a good idea -- typically, crawl spaces need to be ventilated. 

   I imagine that your geographical region and local climate also play a role.  Is radon an issue where you live?

   Post more information here and hopefully you'll get a good answer for your specific conditions.

    

3. 
   MikeHennessy | Jul 27, 2007 09:01pm | #3

   I'm surprised you didn't get more feedback on this one.

   "Boxing in" will give you problems, even if you put down plastic. If you want to fully enclose this space, I'd say you're going to have to go with stemwalls and venting to conditioned space. If you do enclose it (to keep critters out, for example), it needs to be well vented. Insulate under the floor to keep the addition warm. I'd use foam or blown-in celulose, well screened to keep the critters out of the tempting new "nesting area". I believe 18" above grade is the minimum recommended height to permit adequate ventilation. To avoid termites, use treated lumber for everything up to and including the sill plate. Use appropriate termite shields/flashing.

   Mike Hennessy
   Pittsburgh, PA

1. 
   Talma | Jul 27, 2007 09:39pm | #4

   I can add ventalation to the crawl space. But as you mentioned critters are a concern, so I can add some screen windows. How many should I put on a 23' x 18' addition?

   If I put 1/4 ply on the bottom of the space, would this be a problem? To keep out our furry friends out as well as to protect the insulation. Ensuring an 18" min under the crawlspce would be no problem.

   As far as the trim board I notied the local orange box has PVC "boards" up to 10" widths. Would this make a good trim where there is ground contact? With painted plywood above?

   My location is Rochester NY, so we get some good winters. and a few feet of snow is pretty common. My area doesn't have any radon problems and has real good drainage.

   Thanks for the advice. -Tim

1. 
   MikeHennessy | Jul 27, 2007 10:00pm | #5

   "I can add ventilation to the crawl space. But as you mentioned critters are a concern, so I can add some screen windows. How many should I put on a 23' x 18' addition?"

   I'n no expert on this, but I'd say at least one of decent size on each exterior wall -- maybe two on the long one. Make sure at least one is large enough for you to crawl through if (er, when) you need to get under there. You know, to catch the critters.

   "If I put 1/4 ply on the bottom of the space, would this be a problem? To keep out our furry friends out as well as to protect the insulation. Ensuring an 18" min under the crawlspce would be no problem."

   Ply won't stop any rodent. They seem to love chewing on it. If you do use ply, use galv hardware cloth under it. It'll function to hold up the insulation until you get the ply up anyway. BTW, unless you have some sort of stem wall or other barrier below grade, you WILL have furry residents under your addition. Mice, squirrels and chippies at the very least. Possums, skunks, coons and/or porkies possible, depending on your local fauna population. Heck, I was recently at a presentation by a PA Park Ranger who showed pics of a "boxed in" porch that a black bear had comandeered as a den. Chewed the joists down to furring strips -- just because she could! You sure you wouldn't rather just put up a proper block wall to the frost line and be done with it? Hey, I'm just sayin' . . .   ;-)

   "As far as the trim board I notied the local orange box has PVC "boards" up to 10" widths. Would this make a good trim where there is ground contact? With painted plywood above?"

   Not sure what you mean by "trim board where there is ground contact". I thought this was to be elevated 18+ inches. Do you mean you will use Azek (or equiv) to "box in"? If so, that'll work, but it's expensive. I'd use a fibercement product like Hardi over treated framing, but see comments above about a stemwall. Think "stemwall."

   Oh, and you may want to consider constructing a stemwall rather than piers.

   Mike HennessyPittsburgh, PA

4. 
   CapnMac | Jul 28, 2007 12:53am | #6

   What might be better is a solid perimeter foundation wall, which is then insulated right up and continued into the wall insulation above.

   That can seem counterintuitive--but it's a smaller volume to insualte than the entire floor.  What you almost always do no want to do is allow water vapor in under the floor to condense on any thing in there--insulation, framing, whatever.

   But, I'm just words on the internet.  Check out the info at buildingscience.com, they have a number of recommendation based on regions, climate, and so forth.

   Oh, and aim for 24" clear in the crawl space--12" is a bear.  And, ICF make a neat way to build that wall, too.

   Occupational hazard of my occupation not being around (sorry Bubba)