1950s Brick Ranch, No Insulation But Weird Plaster Type Drwall.

personalt

i am doing an addition on a 1950s ranch with a deck off the existing floor. i opened up a wall to a new 6 foot slider and to my suprise i found zero insulation.

House a raised ranch, 8 inch block foundation with a brick facade.

i cut a hole in the wall to check out the framing and found what at first looked like two layers of drywall. what i found most weird was the top(inside layer) had a cement/plaster feel to it while the outside layer loked like regular drywall.

What is this plaster like material? it was paper faced. Why was this used over what looked like drywall. if drywall was available at the time this house was built why would that have been the second layer?

The outside looked like they had a foil paper then black paper then the sheathing then brick on the outside. Today was one of the coldest day of the year in NJ and the inside of the sheathing didnt look cold to the touch.

Other then trying to id the product i am trying to figure out if i want to recommend the customer insulate. We werent going to do much work on the first floor so i dont want to needless open up walls to blow in insulation but if we are going to do it now is the time as they are not moved in yet.

The fact that the sheathing wasnt cold, could it mean there is some rigid foam on outside? or is the brick just that good an insulator?

it i were to punch holes to blow in insulation is there a good tool to drill those holes? i know that drywall eats up hole saw bits really fast.

mdshunk

It's called "gypsum lath", and was basically 2' wide pieces of drywall that had two coats of plaster on top. The foil backing was somebody's idea of insulation in the 60's.

To do lots of round holes, you'd be best served with a remgrit hole saw.

personalt

ok.. that makes sense.. I guess back in the the day before drywall totally took off this was a transisition material.

for the remgrit hole saw bit, any ideas on how many holes i might get though 3/8 of plaster and 3/8 of drywall per bit?

mdshunk

Maybe 500. Just a guess, but probably pretty close.

Here's a guy that has two new 2" ones for 9 bucks each.
http://cgi.ebay.com/RemGrit-2-HOLE-S...QQcmdZViewItem

K2

One thing I found a little interesting about your gypsum lath is that the portland based top coat will not mold but the board behind can be full of mold. Not an issue 99.9% of the time but if you're looking at a basement with this gyp lath and you think it looks good you could be in for a surprise.

On insulating existing exterior walls.

On a 1600 ft sq house you might have 1400 sq ft of outside wall. If you take away doors, windows, headers, corners, and gang studs you might be able to insulate 750 ft sq of wall . Doing blown in through small holes there are likly to be pockets that get missed and some settling at the top over time. That and the fact that an uninsulated wall cavity with dead, (non moving), air does provide some R factor. The more the air is non moving the better the r value.

That's how I presented to customers in the past and most choose to spend those dollars elsewhere.

mdshunk

While that may certainly be true, other guys won't miss an opportunity for a sale.