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Old 02-19-2019, 10:22 AM   #1
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Insulating "void" in basement


I bought my house last year and it was built around 1900. There is a space approximately 4x10' made entirely of brick walls and a concrete floor that is mostly empty space but there is air leaking in from outside into there making it one of the coldest spaces in the entire house. The only access I have to it is a small break in the top of the brick wall and the previous owners knocked that hole in there to allow them to throw construction debris into it (maybe 1' high all the way across the floor) from when they added an addition to the back of the house. It's physically dangerous - maybe even fatal - for me to enter, and the walls are load bearing so I cannot open the wall further to enter more easily. I was thinking about filling it with blow-in insulation, but I cannot get a straight answer about how many CUBIC feet a bag of insulation fills. Also, every seller says blow-in shouldn't be used in basements, so I'm wondering if this is just for GENERAL reasons, or ALWAYS. If always, is there an alternative I should consider that I haven't thought of?

I've thought about just covering the outside faces of the walls with insulation, but the dining room and the bath tub are directly over the void and the floors get COLD, so I need to insulate it somehow from the inside.
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Old 02-19-2019, 11:04 AM   #2
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Re: Insulating "void" in basement


Add a nearby big city to your profile so it will show up with each post. That helps us help you.

I'll assume cold. First thing that comes to mind is the construction debris serving as termite food. If there is wood and junk in there it needs to be cleaned out. If the clearance is only 1' then it will need one of those tiny people who never learned how to eat. Using summer students often works.

I would not suggest just blowing any type of insulation in there as it is serving as the floor for important spaces above. Some pictures of what you are seeing, access and inside would help.

My thoughts are, if possible, insulate and air seal the perimeter which would allow you to add some heat to that space. warming it up would directly help the floors above. Burying it in insulation could restrict air circulation and invite moisture and mold.

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Old 02-19-2019, 01:30 PM   #3
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Re: Insulating "void" in basement


Thanks for replying so quickly. I'll try to clear some things up for you.

1) I'm just North of Boston

2) The construction debris look mostly like brick that was knocked out during the construction of the expanded basement. If there's wood in there, it's minimal. Even if it is, I would have to knock out the existing brick wall to get to it, likely bringing the house down on me; this isn't an option.

3) The space is approximately 7' tall and the small opening would then be almost 6' from the floor. I can only reach 2 of the 4 walls, and cannot tell where the air is coming in from, except that I can feel a frozen breeze when I stick my head and/or arm in there. Since I can't get in there, and the drop is so far into a pile of jagged debris, I don't know how to insulate any other way than blowing in insulation.

4) I'll try to post photos to help make it more clear what I'm talking about.
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Old 02-19-2019, 01:45 PM   #4
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Re: Insulating "void" in basement


Is the ceiling height inside this isolated area 7'? I guess the pictures will tell.

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Old 02-19-2019, 01:46 PM   #5
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Re: Insulating "void" in basement


Attached are 4 pictures. The dimensions of the void are 6x4x6.5'

The outer 2 walls are concrete poured during the addition, and I can't get to them from the outside. The inner 2 walls are brick.
Attached Thumbnails
Insulating "void" in basement-20190219_143537.jpg   Insulating "void" in basement-20190219_143530.jpg   Insulating "void" in basement-20190219_143519.jpg   Insulating "void" in basement-20190219_143420.jpg  
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Old 02-19-2019, 02:10 PM   #6
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Re: Insulating "void" in basement


Above the missing brick, that looks like a substantial beam, if it is, you can open a bigger hole in that area.


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Old 02-19-2019, 02:20 PM   #7
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Quote:
Originally Posted by Nealtw View Post
Above the missing brick, that looks like a substantial beam, if it is, you can open a bigger hole in that area.


My biggest concern is that's the original beam for the back of the house from when the house was originally built, as is that brick is the original border of the basement from when the house was built. And since the house is 3 stories tall, the concern of a collapse is greater.
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Old 02-19-2019, 02:29 PM   #8
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Re: Insulating "void" in basement


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My biggest concern is that's the original beam for the back of the house from when the house was originally built, as is that brick is the original border of the basement from when the house was built. And since the house is 3 stories tall, the concern of a collapse is greater.
Yes the size of the beam required is related to the load above and the width of the opening. I am not an engineer so can't do those calculations but we can see that there is no problem with the hole you have now so just making that hole deeper would not change much to any calculation.
Normally a header for that would be like a 2 ply 2x10 unless there is a more extreme load above. You have a sewer clean out inside so the plan must have been to have an access to the area. I would not be afraid to make a 30" wide opening where the brick is already missing.
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Old 02-19-2019, 03:37 PM   #9
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The cleanout is for the line coming from the 2nd floor to the main stack. Whoever put it in put the line parallel to the earth so I'm glad they put that in the line since I'm snaking it every few months.

If I go with knocking that wall out, how do I prevent it from weakening while I knock it out? Obviously I can't shore the beam until the wall is removed. And I can't afford to pay a contractor to do it for me.
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Old 02-19-2019, 03:58 PM   #10
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Re: Insulating "void" in basement


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The cleanout is for the line coming from the 2nd floor to the main stack. Whoever put it in put the line parallel to the earth so I'm glad they put that in the line since I'm snaking it every few months.

If I go with knocking that wall out, how do I prevent it from weakening while I knock it out? Obviously I can't shore the beam until the wall is removed. And I can't afford to pay a contractor to do it for me.
With out an engineer I would not knock down the whole wall but I would continue down from that opening, that beam is plenty for that.
I would rent something like this, one that has a hose attachment to keep the dust down. and just cut straight done.
https://www.amazon.ca/Evolution-Powe...95987666&psc=1
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Old 02-27-2019, 08:17 PM   #11
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Re: Insulating "void" in basement


I agree that you need to enlarge that hole and get in there in order to address the cold air problem.

It looks like the underside of the wood floor does not have insulation and the rim joist is uninsulated and not sealed with spray foam. I think you need to seal and insulate the rimjoist. Maybe even the floor. Depending on what walls there are exterior walls, you could also apply foam insulation sheets to the walls to keep the cold out.
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Old 02-28-2019, 05:14 AM   #12
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Re: Insulating "void" in basement


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I agree that you need to enlarge that hole and get in there in order to address the cold air problem.

It looks like the underside of the wood floor does not have insulation and the rim joist is uninsulated and not sealed with spray foam. I think you need to seal and insulate the rimjoist. Maybe even the floor. Depending on what walls there are exterior walls, you could also apply foam insulation sheets to the walls to keep the cold out.
The floor has what looks like R11 insulation, but it's poorly shoved in there and obviously a remnant of before the addition was added to the house. 2 of the walls are to the outside that look like they tried to at least insulate the spaces between the framing and the concrete foundation, but there's waaaaaaay too much air coming in still. I can't find it without going inside.

I got a quote from a masonry contractor who said it will cost me $750 just to cut the wall out and brace it for me to get in there. Then I have to get the spray foam, which I only was able to find for $550 (including the sprayer). I hope it's worth it... At the very least my feet won't be turning to ice as soon as I step into my bathtub anymore (it's directly over the void). If this doesn't fix that, then I know there's a hole that leaks into the space under my tub and I'm NOT looking forward to tearing that out to find it...
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Old 02-28-2019, 07:13 AM   #13
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Re: Insulating "void" in basement


I would listen to what the mason was saying he would do ... and then do that myself.

Or how about this:

1- Run an extension cord in there and hang 2-3 temporary lights from the ceiling so you can see what your doing.

2- out of 2x4s build a ladder sized to allow you to climb up and in to that hole.

3 - build another ladder that you would slide through the hole so that you can climb down on the other side.

4 - Cover the jagged tops of those bricks that you have to shimmy over with a couple layers of heavy moving blankets from Harbor Freight. This will minimize the cuts and scrapes you get coming in and out.

5 - Once in there you can assess what needs to be done

Spray foam is great, though I have never used those DIY kits. But you should be able to achieve the same result with a few cans of great stuff ($10 each) a pro gun for spraying them ($50) and a bunch of foam sheet insulation. Around here you can buy recycled (used) foam sheets on CL for about half what they cost at HD. That would work perfectly for your situation.
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