Jump to content
Sign in to follow this  
Jim Baird

"Ghosting" on hardi-type siding

Recommended Posts

House about 10 yrs old. This color diff pattern appears to show us stud locations, as the dark vertical lines coincide with face nails, but I don't know why. Guesses?

Click to Enlarge
tn_20161128222041_PB280035.jpg

54.64 KB

Share this post


Link to post
Share on other sites

Insulation issues? Maybe temperature differential causing the finish on the siding to wear in that distinct pattern.

Which direction does that wall face? Was there similar patterns on other sides of the house?

Share this post


Link to post
Share on other sites

I don't know the reason, but I see it fairly often. (OK, maybe only once a year or so.) Perhaps it's the same thing as happens when the nails aren't driven quite far enough, touch the siding, and cause color changes.

Share this post


Link to post
Share on other sites

It's a full open eastern exposure. Other side is shaded by adjacent house for part of the day. I too think it is temp diff between area over framing and area over substrate, which is likely half inch isocyanurate and likely foil covered where structural sheathing is not applied. Also is likely the only coat of paint it ever had.

Share this post


Link to post
Share on other sites

Probably the same phenomenon as ghosting on the interior with candles, etc. Dust particulates depositing unevenly due to thermal differences showing thermal bridging at studs, etc.

I doubt there is foam board in those areas, but then 1/2 inch is pretty skimpy for much thermal benefit.

Share this post


Link to post
Share on other sites

Probably the same phenomenon as ghosting on the interior with candles, etc. Dust particulates depositing unevenly due to thermal differences showing thermal bridging at studs, etc.

I doubt there is foam board in those areas, but then 1/2 inch is pretty skimpy for much thermal benefit.

I thought the same thing, but it won't scrub off. The vinyl itself actually changes color.

Share this post


Link to post
Share on other sites

The photograph gives me the impression that there is also a dark horizontal strip approximately where the 2nd floor rim joist would lie. It appears to match the color of the suspected stud markings. If that coincides with the actual appearance, the framing is certainly affecting the issue if not directly causing it.

Another thought is that periodic, subsurface moisture might have "washed" some of the zinc from the fasteners slowly over time. Precise nailing on the studs would keep the drainage rather vertical. Weep holes would drain the wash close to the nails.

Are there any evidence of irrigation over-spray or misting?

Share this post


Link to post
Share on other sites

Something I see here sometimes is frost forming only where the studs are.

Moisture collects on those cooler strips, but why that would darken paint, I don't know.

We sometimes get algae growth in that pattern, the green slime that turns dark when it dies.

Share this post


Link to post
Share on other sites

House about 10 yrs old. This color diff pattern appears to show us stud locations, as the dark vertical lines coincide with face nails, but I don't know why. Guesses?

Click to Enlarge
tn_20161128222041_PB280035.jpg

54.64 KB

Moisture movement from the interior to the exterior. Any water related issues in the home?

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  



×
×
  • Create New...