A couple of question about exterior foundation wall insulation and drainage...

[Jeff]

Hello,

We are having a house built in Virginia and need some advice about whether or not to use 2'' expanded polystyrene on the outside of the foundation walls. The basement will be totally underground. I want to make this space as liveable as possible to be able to rent it out some day.

I've heard good and bad things about the application of EPS to below grade foundations. Is this a proven technology???? I've heard that it will eventually absord water and start to deteriate over time. The weight of the backfiill tends to crush it somewhat, reducing its insulation properties somewhat. Should I stay clear of it? If not, should I use expanded or extruded poly?

Also, I want to install a drainage mat against the insulation. The drainage mat will be facing the soil. But I have no intention of tying the drainage mat to an exterior French drain to remove water that might seep down arounfdthe insulation. Can I get away installing the drainage mat without having it connected to a French drain. Or is this a bad idea? The lot/grading does not allow for an exterior French drain empting to daylight

Thanks to all those who reply....

[Lyle B. Harwood]

? Also, I want to install a drainage mat against the insulation. The ? drainage mat will be facing the soil. But I have no intention of tying ? the drainage mat to an exterior French drain to remove water that ? might seep down arounfdthe insulation. Can I get away installing the ? drainage mat without having it connected to a French drain. Or is this ? a bad idea? The lot/grading does not allow for an exterior French ? drain empting to daylight

What do the blueprints say?

What does the architect say?

Why are you asking us instead of them? Have you lost confidence in your designer?

We can't see your site from here, and can't answer your questions.

Best of luck, and let us know how it comes out!

[Joseph Meehan]

Lyle made some very valid points. The questions you are asking have a lot to do with local conditions. The water table and soil type as well as weather is critical in deciding what will or will not work. Also some areas will have code requirements, especially if you plan to rent it out. Have you checked the local code requirements?

While I am a fan of insulation added to the outside of the foundation, I have not followed the current technology so I can't offer an opinion. However I can say that 20 years ago when I was building a home, my builder thought I was crazy when I added foam myself before he backfilled. Ten years later with the same builder, it came as standard.

[Jimmy Galvin]

[Jeff]

There is no architect involved. It is just the builer who is a cheap ass who will not do anything more than the minimum required by the building code. I want to do the basement insulation and waterproofing myself since there seems to be a lack of knowledge on the part of most waterproofing companies in this area. If you call them up or visit them in person they give you the dear in the haedlight stair when I explain what I want them to do.

[Frank]

Lyle Harwood is a freak!

[Trent©]

My standard suggestion...

1. Tile/drainage around the inside perimeter of the basement.

1. Tile around the outside perimeter of the basement.

2. Cross-over...tieing the two together...draining to sump hole and pump.

1. Risers to grade with cleanout caps from the tile at 2 opposite ends of the house...for future cleaning.

2. Porous stone (#6?) as backfill alongside the walls to within 2 ft. of grade...poly...good soil to grade.

Lots of details missing, of course.

Check with your local building inspector. Tell him what you have in mind. Get his demands...but also his opinions.

A few weeks ago, someone posted an excellent site...describing in detail what I've said. Sorry to say, I didn't keep the link.

Good luck.

Have a nice week...

Trent

Help keep down the world population...have your partner spayed or neutered.

[Lyle B. Harwood]

? Would you mind elaborating a little more on this? What specifically ? is it about the soil type, weather conditions and water table that wil ? or will not make it work??

Jeff, that's the part we can't see.

Every site is different. Every situation is different. Every soil type and combination of variables is different.

There are professionals who anaylize specific sites and create specific designs.

They are architects and engineers, and you need a design created by a professional design team. I asked you what the blueprints show, and what the architect said, and you answered that there is no architect.

If it's true that there is no architect and no design, you are right to be concerned, because you are in trouble.

No one here can help you, and your questions indicate to me that you aren't capable of creating the design yourself, and that you have no confidence in your builder's ability to create the design. On top of that, your site may very well require a system that you aren't capable of installing by yourself, either.

I urge you to consult a licensed local architect who has a record of success with the types of challenges that exist on your site.

Best of luck, and let us know how it comes out!

[Kevin]

Fine Homebuilding did an excellent article on this in the last couple of years, I forget the issue, try their website.