Q&A: A Forum for Green Building Experts and Beginners

Q & A Instructions

[Click map to enlarge]

The GBAGreenBuildingAdvisor.com web site has a wealth of articles on a wide variety of construction topics. Before posting your question, you may want to check out the articles on this page: How To Do Everything. You just might discover an article there that provides the information you seek.

Please register for a free account or sign in to ask and answer green building questions.

If you want to post a question, the usual rules of courtesy apply:
1. Be nice.
2. If you can't be nice, be polite.
3. If you can't be nice or polite — well, please be brief.

To attach a photo or illustration: Under the box labeled “More explanation,” look for the words “File attachments.” Click that, and you should be able to attach a photo.

Thanks for joining the conversation!


4 Answers

Why am I supposed to seal ventilation baffles?

One reason for venting a roof (in addition to keeping the sheathing cold) is to release moisture from the attic. Given that (and assuming it is a given) I'm a bit unclear on the benefit of air-sealing ventilation baffles, particularly in a cathedral ceiling application where the baffles are continuous from soffit to ridge.

Asked By Christopher Wegscheid | Jun 15 17
4 Answers

Adding exterior insulation to 100 yr old house - added risk for rot where framing contacts foundation?

Going to add exterior insulation (spray foam likely) over 1 layer of siding. The house has a rubble foundation with no capillary break between the foundation and the framing. The ends of the floor joists are embedded in the foundation.

The house had 2 layers of siding. I've removed the outer layer to expose the inner and found the inner siding and sheathing rotted at the bottom of the wall where it covered the band joist and sill. See pictures. Luckily, the joist itself is in good shape.

Asked By TIM LANGE | Jun 14 17
4 Answers

How do I seal the slab edge in my basement around Stego Wrap and foam?

My basement slab has been poured, and I'm ready to cut back the Stego Wrap and 1/2" foam at the perimeter of the slab.

Is there a durable, low VOC sealant that would be ideal for filling the gap between the Stego Wrap and basement wall?

After this edge is sealed, is there a good way to dress this area up? Is there a specific kind of moulding that would nicely cover this slab/wall connection without taking up too much space? The only finish on the concrete walls will be primer and paint, no drywall, and for the floor probably only a sealer.

Asked By Eric Whetzel | Jun 13 17
3 Answers

Sub Basement Crawl Space

In the planning stage for steep slope home in North Carolina. After the topo survey results came in today, it is obvious we will need a crawl space under the lower level(will have main floor, lower level, then crawl space below due to steepness of lot). The foundation will step down on the sides. The way the builder describes it, they generally leave dirt floors, then encapsulate and condition this space and spray foam the walls. Seems to me I would rather treat this crawl like a mini-basement.

Asked By Kevin Spellman | Jun 14 17
1 Answer

Where should I caulk the exterior of these windows?

The thin-coat plaster blistered up through the paint just below the window apron in our 1938 house. I removed the loose plaster and patched and repainted an area of about 2 square inches. The bulging plaster seemed quite dry despite recent rains. I'm guessing the damage was due to rain, perhaps wind-driven rain. Climate zone is 6A if that matters.

There's no caulk between the aluminum wrapped window and the stone sill below it. Should I caulk it, or might that block drainage? The stone sill slopes, which isn't obvious from the picture.

Asked By Jonathan Beers | Jun 14 17
4 Answers

Airtight Drywall vs Airtight Exterior

Hey all.

I read the post here: http://www.greenbuildingadvisor.com/articles/dept/green-building-blog/ho...

It's now a couple years old. I still hear of Air Tight Drywall frequently on here and other sites.

What on earth is the purpose of sealing drywall corners and joints with foam and caulking when you have to mud all these joints, corners, seams, etc. prior to priming and painting the drywall?

Asked By Nicholas C | Jun 14 17
2 Answers

Double stud wall details

We are in Minnesota (Zone 6a). 2200 sq/ft single level (9' walls), slab on grade.

I can't seem to find much information one way or the other about 2 particular details of a double stud wall. Thoughts?

1. What are the advantages and disadvantages to put the studs in line with each other or to stagger them?

2. What are the advantages and disadvantages to build them 24" OC or 16" OC?

Asked By Scott K | Jun 13 17
3 Answers

Concrete porch meets foundation insulation - detail

We are in Minnesota (Zone 6a). 2200 sq/ft single level, slab on grade.

Can anyone explain, or point me to a detail that shows a good way for a patio, porch or garage apron to meet the perimeter insulation of a slab foundation? I plan on 4" (r-20) of perimeter insulation.

Is it as simple as removing the foundation's 4" of perimeter insulation the thickness of the patio slab and replace with 1/2" expansion material?

Asked By Scott K | Jun 13 17
1 Answer

Applying exterior foam to stem wall -- water proofing

I am building a slab foundation with a stem wall and 4" of rigid EPS applied to the outside. I've read various GBA advice about fasteners/adhesive to install the foam, and about how to coat/finish the foam so that it looks nice. But I remain confused about a couple of things.

(1) Do I need to seal the concrete before installing the foam. A product like STYRO Industries Grey FlexCoat Brush on Foundation Coating has instructions for putting the sealer on the outside of the foam (http://www.homedepot.com/catalog/pdfImages/e9/e96f41fa-e55e-4165-ae4a-17...).

Asked By John Huber | Jun 14 17
16 Answers

Soaked subfloor: Advice on what to do?

Hello,

A huge storm rolled in over the weekend while I was out of town for the weekend(several inches of rain and hail). I actually have 90% of the roof sheathing done so majority of the house floor is fine but the end that was exposed got soaked. When I got back home, much of the section that is wet has black spots all over it.

I'm not sure if this is mold or just dirt/mud/some other substance. The likelihood of mold growing in 3 days seems low but there could of been some organic materiel on top of the wood to encourage growth. What do you guys think?

Asked By Tommy87 | Jun 11 17
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!