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Questions on ground floor room under floor Insulation and Vapor barrier

Questions on ground floor room under floor Insulation and Vapor barrier


Old 09-27-05, 11:22 AM
Thread Starter
Join Date: Jul 2005
Location: Boston, MA
Posts: 36
Questions on ground floor room under floor Insulation and Vapor barrier

OK, what started as removing two closets has turned into the complete gutting of a room. I have now rebuilt, re-pointed, dried out and sealed the walls that were the issue, cleared all of the rotten and eaten wood and joists, decomposed rats, droppings, silverfish, carpenter ants, molding and damp insulation, all the floor (sans the 5 healthy joists that were left), all the dry wall etc. out as well as solving the external drainage and guttering problems that were the original cause. (This is a new home for us but an old house (1900) and all I was doing was ripping out the closest, LOL) Ive also treated all remaining wood with Borate and also treated the dirt floor.

The room is 15ftx9ft and is in a single story brick built extension on the ground floor of a brick built house. Location is the wonderful city of Boston, MA, hot and ****ty in the summer, cold and miserable in the winter.

Anyway, this is where I am up to now, I have a sub floor which is 2x10s on 18 centers and there isnt much space between these and the ground underneath (1/2 2 variable). All interior walls are back to the inside of the 9 solid brick walls. The ground underneath is earth and seems to have dried nicely as Ive been working. I just finished the 2nd coat of 5star waterproofing on all of the newly re-done walls and am ready to start rebuilding the room.

I bought a good 10mil vapor barrier from the builders merchant as it was at a good price (<$90 for 20ftx100ft).

I need to replace all of the joists that were adjacent to the walls because they were either rotten, on their way to rotten or eaten. So was going to do this framing work first.

My plan was as follows;
1) Put the vapor barrier on the dirt under the joists and extend it above the wall. Im also going to extend the vapor barrier against the sealed brick, up to the ceiling (I have plenty) and tape it to the barrier extended up from the floor.
2) Put foam insulation in the small 1 space Im leaving between the vapor barrier on the wall and the joists.
3) Put craft backed insulation between each joist with the paper up
4) 5/8 Plywood
5) Frame my walls with 2x3s and use craft back insulation between the studs

Does this seem like the right way?

Reading some information on this forum and some of the links from here Ive noticed that the recommendation for the vapor barrier would be above the insulation not against the floor, or should I put the vapor barrier on the dirt and up the inside of the walls and another between the floor and the joists? (I have plenty of the VB)

Is there a recommendation for what to put between the joists and the wall in respect to insulation? I was going to use the polystyrene type of foam (pink stuff for HD)

What type of insulation is recommended for between the joists?

If it helps, this is a shot of what Im basically looking at. This was taken prior to finishing off the walls but may help for my questions relating to the floor, insulation and vapor barrier, etc.

www.rags2richies.com/The Project_096.JPG

Hopefully somebody can help.

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Old 10-02-05, 08:00 PM
Join Date: Aug 2000
Location: USA
Posts: 15,834
Plastic vapor retarder over the soil. Styrofoam on foundation walls. Batt insulation with vapor retarder facing up toward heated space. Studs are usually 2x4s. Many are going with 2x6s these days, especially if wall is a plumbing wall. Most go with 3/4" thick tongue and groove plywood on the floor. The sheets are both nailed and glued to prevent squeaks. Vapor retarder on insulation for walls will face the heated side of the room.

Professional treatment by exterminator is recommended. They have the equipment the chemicals not available to the consumer. They force termiticide deep into soil on both sides of the foundation to create a barrier against termites and other wood boring insects. Exterminators guarantee their work. Maintaining the contract for the annual inspection is important for spot treatments and keeping track of any problems. It's a worthwhile investment to protect the investment in your property.
Old 10-04-05, 06:16 AM
Thread Starter
Join Date: Jul 2005
Location: Boston, MA
Posts: 36
Thanks for the feedback.

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