Overhung Bathroom Floor - Insulation - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Insulation

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Like Tree2Likes
  • 1 Post By Windows on Wash
  • 1 Post By Nealtw
Reply
 
Thread Tools Search this Thread
Display Modes
Old 01-14-2019, 11:28 AM   #1
Newbie
 
Join Date: Jan 2019
Location: Leominster, MA
Posts: 4
Rewards Points: 8
Default

Overhung bathroom floor


Hi everybody,

First time poster, hoping to get some help with my first home. It had a bathroom added on to the back of the house a few years back and the overhang looks like it was never properly insulated, just pink fiberglass shoved in there from the basement side. I'm able to stand directly underneath it and it's got a box about 8' wide, 4 ' deep, and 18" tall. From inside the basement, I can see directly into it and saw that they have the floor joists nearer the bathroom floor running east-west and another set of joists on the bottom over the overhang running north-south and there's about an 7"-8" gap in between. In all there's about 18" of space inside vertically. My thought is to remove the plywood sheet from underneath the overhang, pull out all the fiberglass, use Rockwool R23 (15.25" x 47") and fill those top floor joists that are right below the bathroom floor. Then install 2" XPS around the interior of the rectangular box with spray foam on the edges/corners to prevent air leaks and leaving the bottom joists alone. I've attached a mockup I made in Sketchup to try and convey the idea that I have. I'm certainly new to this so I'm just looking for advice if I'm on the right track or if I should go a completely different path.

Edit: I just wanted to add, I'm about an hour west of Boston. Temperatures this weekend were below freezing so I had to thaw our pipes, hence my sudden interest in this topic.

Thank you!
Attached Thumbnails
Overhung bathroom floor-bathroom-overhang-2.png  

Last edited by rscturner15; 01-14-2019 at 11:35 AM.
rscturner15 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 01-14-2019, 01:49 PM   #2
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: Washington DC Metro Area (VA, MD, DC)
Posts: 26,013
Rewards Points: 818
Blog Entries: 41
Default

Re: Overhung bathroom floor


Whats the exterior access look like?
Windows on Wash is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 01-14-2019, 02:16 PM   #3
Newbie
 
Join Date: Jan 2019
Location: Leominster, MA
Posts: 4
Rewards Points: 8
Default

Re: Overhung bathroom floor


It's basically a plywood box, definitely not air sealed, the bathroom floor above it is frigid. I'll include a few photos below.
Attached Thumbnails
Overhung bathroom floor-img_20190114_151011.jpg   Overhung bathroom floor-img_20190114_150954.jpg  
rscturner15 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 01-14-2019, 02:53 PM   #4
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: Washington DC Metro Area (VA, MD, DC)
Posts: 26,013
Rewards Points: 818
Blog Entries: 41
Default

Re: Overhung bathroom floor


Best way to do it is allow the insulation to sit on the bottom of the joist bay, blow or circulate some conditioned air in the joist bay in the open space, clad the exterior with foam that is sealed up and ultimately covered to protect it.



Putting foam on the exterior will create a thermal break in the assembly and will move all the framing (currently weak points in the assembly) to inside the warm wall and make them more efficient.
Bud9051 likes this.
Windows on Wash is offline   Reply With Quote
Old 01-15-2019, 11:54 AM   #5
Newbie
 
Join Date: Jan 2019
Location: Leominster, MA
Posts: 4
Rewards Points: 8
Default

Re: Overhung bathroom floor


Ah ok. If it's not possible to have conditioned air blown into the joist bay, would you still recommend insulating the bottom bay and cladding the exterior of the box with 2" XPS?
rscturner15 is offline   Reply With Quote
Old 01-15-2019, 12:08 PM   #6
retired framer
 
Join Date: Jun 2017
Location: Fraser Valley BC Canada
Posts: 37,852
Rewards Points: 314
Default

Re: Overhung bathroom floor


All that caulking will only trap water from draining out of the deck and shorten it's life.
The gaps you can see thru from the basement should have solid blocking. The space blow the floor can be filled with insulation and instead of plywood the bottom can be vented soffit to help it deal with water that does make it's way in there. Fiberglass insulation is not the best if there are chances of water getting in.
With out heat all the insulation in the world will not make the floor warm.
What kind of heat do you have?
Windows on Wash likes this.
Nealtw is online now   Reply With Quote
Old 01-16-2019, 09:39 AM   #7
Newbie
 
Join Date: Jan 2019
Location: Leominster, MA
Posts: 4
Rewards Points: 8
Default

Re: Overhung bathroom floor


The basement side is blocked off with 2" XPS and spray foam so that's not an issue. I wouldn't say that I'm looking to make the floor warm, I'm more concerned about the amount of air that is definitely present inside that overhang, it's practically so cold inside of there, there might as well not be any wood/foam at all. There is an electric heater in the bathroom and it's not far from our forced hot air for the rest of the house. I'm just hoping to be able to seal up the box from the inside using XPS and spray foam and just have something better than compressed fiberglass everywhere.
rscturner15 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Carpet in the basement Packer Backer Flooring 17 11-30-2018 02:10 AM
NEC - what is the purpose of some of these codes ? chez bouton Electrical 32 12-17-2013 02:04 PM
no framing concrete slab bathroom floor needs to be repaired in one spot barrr Flooring 1 05-15-2012 09:01 PM
Help with ceramic floor bathroom lornescot Flooring 0 11-19-2011 12:35 PM
New foundation for bathroom floor and exterior wall studs JayG Building & Construction 2 07-11-2010 01:25 PM




Top of Page | View New Posts