Should Felt\Tar Paper be used on a 1973 mobile home before new siding is installed

[David Banner]

I'm replacing some old LP Smart Side siding with same. I could staple felt paper across the studs to add a water barrier. I would staple to stud framing, since no sheathing was ever included in these cheaply made mobile homes. ( which also has to do with extra weight\sagging issues of course , but that is a whole other topic) My confusion is, I don't know if putting up felt paper will stop moisture that is trying to escape from the interior of home thus causing mold issues over time. So maybe I should NOT put up felt paper? I could use TYVEK instead, but I hear the pro's still like felt paper over Tyvek.

[Downaski]

Your concern about trapping interior moisture is really valid, especially in a mobile home without sheathing where moisture management is much trickier.

Both felt paper and Tyvek are designed to be breathable, so they shouldn't completely trap moisture trying to escape from inside. However, Tyvek breathes much better than felt paper, making it less likely to cause the moisture buildup you're worried about.

Since LP SmartSide panels sit flat against whatever barrier you use, there's less air gap for drying compared to other siding types. This makes choosing the right barrier even more important. Tyvek's superior breathability could be especially beneficial in your situation.

Without sheathing, you definitely need some kind of water barrier to protect your framing, but Tyvek might be the safer choice since it allows more vapor transmission while still blocking water from outside.

Make sure you have good interior ventilation, like bathroom fans, to control humidity at the source. The key is balancing protection from outside water while still letting interior moisture escape, and Tyvek handles that balance better than felt paper.

[David Banner]

Thanks for the info! I totally understand the Tyvek difference. I only need 5 ft wide x 10 ft. high. but it's sold in huge rolls for $200 or more.

[Downaski]

You're welcome. I understand where you're coming from. For a 5 ft by 10 ft area, it might be worth checking with a local contractor, hardware store, or even browsing places like Facebook Marketplace or Craigslist. Sometimes people have leftover Tyvek from a job and are willing to sell smaller pieces at a low price or even give them away.

If that doesn’t work out and you end up using felt paper, just make sure your interior stays well-ventilated to help manage moisture. Good airflow, like using bathroom or kitchen fans, can go a long way in keeping humidity levels down.