Ok...here's the situation....my house has a brick foundation. The previous owners added a room to the house with it with its own cinder block basement. The two basements butt up against each other and I want to connect them with a door. As far as removal of material and door installation, I can handle both easily. The concern I have is structural integrity of the wall. I have two questions:

1. Can I remove a 1 foot square section from one wall, to assess the situation between the walls, without the house falling down?

2. Would it be sufficent to support the joists nearest the pending opening with 4x4 posts until a proper header is installed?

Not hitting this project until spring, so I'm not in a big rush...any suggestions are appreciated

 

Yes a 1 foot square hole can be made in the wall (I suggest the brick wall) without the wall failing, barring doing it where there are large cracks or other problems with the wall. I suggest the brick wall because then you can build a frame out of 2x4 to place into the hole until you do the doorway later. Some drywall or plywood screwed to this frame will cover it over nicely.
As far as the doorway, if it were me, I would make the openings from floor height to the sill plate. Fill the floor area with concrete and level with the finished floors in the basement. It will depend on how deep the opening is when opened up as to what size frame you need to install. If the block was laid right against the brick then we are talking about a hole 11 1/2 inch wide. Perfect for a 2x12. Build this frame from floor to sill plate. 2x12 across top screwed to the sill plate. Then 2x12 sides toe-screwed to top plate and lagged to the blocks and brick sides. Then your built up header goes next with 2x12 sides holding it up. Depends on the height if you will need cripples on top the header or not. If it is 8 feet (96 inch) you can simply add an extra 2x12 to the one against the sill plate and a 2x12 header will fit nicely.
I would build the header the following way, double 2x12 on brick side, 2x12, 5 inch long spacers (3), and a 1/2 inch plywood piece between them. All this would be screwed to the extra 2x12 for the top before it was installed.
Then the 2x12 jack studs under the header would complete the doorway.
How big a hole you cut would depend on if you plan to install a door there. I would make the hole big enough to be able to install a 36 inch pre-hung door. that means the opening needs to be cut at least 44 inch wide.
If you notice I am trying to explain making the doorway the same as a doorway is built on a regular house wall. 2 king studs all the way to the top and 2 jack studs holding up the correct sized header. The only real difference is it will be built from 2x12 instead of 2x4.
You can cut the brick with a masonry blade for your circular saw.Then you use a hammer and chisel to remove the bricks starting at the top and working down. Then after that hole is finished you will need to cut through both sides of the block wall before you attempt to remove it. I believe you can still buy masonry blades for a reciprocating saw. That would work great on the block wall from the brick side. If not you may have a rough lookin opening when you bust the blocks out. NO don't just sledge hammer the thing open. You want to keep the hammering to a minimum to reduce the chance of cracking the walls where you don't want them cracked.
Put up a temporary support wall in each basement to keep the floor sag to a minimum before you start. Please don't take my measurements as correct. It was on the fly that I came up with those and yours may vary. But at least you got an idea of how to do it.

 

Wow...that was an even more detailed answer than I was hoping for...thank you! Still have one question though...for the temporary supports whilst installin g the header...is 4x4 post under the joists on either side of the proposed work opening on both sides of the wall enough support? Total of 4 post with 3 joist in between them. I suppose I could also put a temporary "header" between each pair of posts to ease the strain on the unsupported middle joists. I've only done window headers on a top floor before....lot less weight to deal with.

 

If I were doing it I would use a 4x4 across the top as a header and only support it with 2 more 4x4's. You would only be supporting a 6 foot span.
They are probably not even needed for a 4 foot wide hole but better safe than sorry. Be sure you screw the temporary support to the floor joists and each other so there is no chance for them to be knocked down.

 

Keep in mind that a 4x4 is no stronger than two 2x4's when used for a header. But like he says it would probably be fine. If it was me, I would just build a solid temporary wall under the area, 16" OC, and then screw a sheet of plywood on it for good measure. Depending on how much weight you are dealing with, of course.

 

Thanks, both of you. I feel a lot more confident moving forward. I will let you know how it goes.

 

I hope your floor joists are perpindicular to the wall the door will be installed in.

If the joists at this location run parallel to that you are going to have to remove a couple of blocks in top course just out side your rough opening for the door in order to support the rim or outside joist. Just take a heavy hammer and pop holes centering over the cores on each side of the center of block. Keep increasing the diameter of the hole until you get to the cross webs. Now, carefully remove the mortar from outboard block because you can tuck a replacement 8" block back in when the door header is in the wall and those 2x8 headers are gone. By removing those two blocks you should now have room to slide a 2X8 header perpindicular to the wall the door is in. If joists run parallel to door wall iinstall a length of joist doubling up the existing outside rim joist long enough to span block opening This information is assuming the floor joists are parallel to door wall. If they are perpindicular, you already have good useful help in this thread.

Once you have supported the joists it is time to cut the block opening. For this job, I have to say rent a 14" diamond blade concrete saw. Carefully pick the location. You are going to want to minimize cuttiing through as many block webs as possible. If you do have cut through webs you can do it with that saw. By the same token, be careful with the cut sides when the cut goes through a block core because it can be easily broken. Get the two vertical cut lines perfectly plumb, completely through the block and straight so when block are cut you can wedge your wolmanized 2x8 across the newly raw or cut end of block. These can now be your studs and btw use it as a form also. If you are crafty enough you can get a couple sacks of pea stone quick crete and grout those cores for a nice solid opening. Attach 3 3/8 or 1/2" bolts to your stud (mortise the nut and washer flush with inside of opening so as to leave room for your jack studs. For a 3/0 door the R/O would be as somebody already pointed out 44". I'd say that's right but you might add 1/4 to 1/2" to clear the inside measurement between studs & DOOR wood brick mold depending on where the door is set. R/O 38" + thickness of two studs and two jack studs.

if placed precisely in the right position of the block core, 44 1/2" will accomodate a nice grouted border on each side of door opening and give you a great place to anchor plugs for mechanical attachment. (wood stud to concrete block using three anchor bolts per side)

This is a job for a professional. If in doubt please hire one. Be careful out there.

bs5

 

By the way, you had mentioned opening up a one foot hole in a brick or block wall. go ahead and do it. Heck, you could shoot a 108 mm howitzer round right through that wall and it probably would not seriously damage the integrity. This is exactly what happened in Europe and Iraq during wartime and there are hundreds of pictures available of examples to prove it.

How can this be? Any opening or breach to a brick masonry structure forms an arch over the opening. The natural arch is present even if the hole is toothed by modular units. Stone and brick bridges over creeks and rivers have existed for years based on the physics of an arch. Of course an arch has to have certain a certain content or mass available on the sides and over the top to be secure.

Don't try this at home though. It doesn't take a world war to inspect a brick wall just a little sweat and a few tools will do nicely.



bs5