New Tuckpointing in Older Basement Walls

Reading through this forum is a lot of fun....thanks to all the experts who contribute their time and expertise. Slowly I'm realizing how much I'm learning..and how much time it all takes, but it's fun!

I have a 110 year old house, with basement walls consisting of rubble stone topped with red brick. I have a few questions.

These were covered with a coating of mortar that is coming off in big sheets and bits. The tuckpointing is turning to sand in many areas. I am about to start new tuckpointing, but wanted to get some expert advice on the cement/mortar mix. I have heard of issues with old bricks not agreeing with new cement/mortar.

In addition, I have several bricks that are flaking apart, even though they are dry. Am I correct in thinking they should be replaced as there is noting that can really be done to prevent them from deteriorating further?

Lastly, some of the brick sections have been painted white. What is the best way to remove the paint, light sandblasting? I want to return the walls to their natural brick and stone.

As always, thanks!

vince

1victorianfarmhouse said:

These were covered with a coating of mortar that is coming off in big sheets and bits. The tuckpointing is turning to sand in many areas. I am about to start new tuckpointing, but wanted to get some expert advice on the cement/mortar mix. I have heard of issues with old bricks not agreeing with new cement/mortar.

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There are several issues you need to address. First off, you want to ensure that the mortar mix you use is softer than the brick. That's because if excessive moisture gets into the masonary and expands as it freezes, you want the mortar to break rather than the bricks. So, the first thing to do is check with your local masonary contractors to see if a standard Type N mortar is suitable for use on your walls. Also, if there are areas of exposed bricks and mortar, it's worthwhile to experiment with various mixes if what and grey portland cement to match the colour of the old mortar so that your repair is less noticable.

In addition, I have several bricks that are flaking apart, even though they are dry. Am I correct in thinking they should be replaced as there is noting that can really be done to prevent them from deteriorating further?

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"Flaking" of the surface of the brick is called "spalling", and it's caused by excessive moisture getting into the brick and freezing. As the H2O freezes into ice, it expands and the brick breaks in the direction it's least able to resist breaking, which is near it's face. Take a look at the the way the bricks in the picture below are breaking. This kind of breaking away of the surface of the brick is due to excess moisture inside the brick freezing into ice.

Lastly, some of the brick sections have been painted white. What is the best way to remove the paint, light sandblasting? I want to return the walls to their natural brick and stone.

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I'd say sandblasting or with a water jet. The paint used on the brick may have contributed to the spalling. Oil based paints are impermeable to moisture, so they tend to trap moisture in the wall behind them. If you ever paint masonary, be sure to use a paint specifically made for painting masonary. Such paints are called "masonary paints" and they will normally be a latex paint whose resins are chosen specifically because of the ability of H2O molecules to pass through the paint film easily.

You don't need to know the rest:
Often people cannot understand how it is that a masonary paint can prevent liquid water from passing through the paint and into the wall, but that same masonary paint will allow moisture in the wall to evaporate through the paint.
Think of an acrylic resin as a wire that's been scrunched up into a ball. There are small gaps between the segments of wire in the ball. With masonary paints, those gaps are larger than the diameter of an H2O molecule, but smaller than the average distance between H2O molecules in liquid water. So, individual H2O molecules can pass through the paint relatively easily, but liquid water cannot pass through the paint. Consequently, a masonary paint allows moisture in a masonary wall to dry out without allowing rain to pass through the paint into the wall.

http://www.cement.org/masonry/cc_mortar_types.asp

Hi Nestor,

Thanks for the great and dvery informative post, especially about the mortar mix.

The spalling on some bricks has me stumped. Not all bricks suffer from it, and they are random. Some are high and dry on both sides

The basement is pretty dry; I have not seen any humidity issues or flooding, even with heavy rain and ground moisture from melting snow. I do know that in the past the basement has been flooded with an inch or two of water, but this was probably due to leakage from the plumbing and not from outside (like when the washer drain tube came undone recently).

I have noticed that there are two walls, an outer (with decorative limestone on the outside) and an inner, and there is a gap between them. Hitting the bricks with a hammer sounds like there is a hollow back there. Is this normal?

Sandblasting will probably be the way of choice for paint and tar like stuff on some apots.

Once again, thanks!

vince

Well, y'all know more about this than I do...

I agree on excavating the outside and am planning to do this as my cousin is a long time waterproofing/drain tile contractor and will let me use his equipment and hire a few guys to help. Definitely later this year.

The part that I want to ask him about is the hollow walls. Hmm. The spalling isn't consistent, and may well have been that some of the 110 year old bricks are not from a good batch.

No plans to paint the inside walls. Interesting comment about the peach pits or walnut shells. I've done this with car and cycle stuff and again, this is something I want to look at carefully.

Thanks!

vince

The void between the walls is normally the way it is done. Usually about a 1" gap.

The void allows for expansion movement when the back wall and front wall are constructed of two different materials and the void also allows for a place for the purging mortar to go during wall construction.

Hi Bud,

Thanks for the good info about the gap. Makes sense....but my gap is about 8" deep. Some loose bricks have been pushed into the wall and fallen down there. That is why I was curious.

vince

....but my gap is about 8" deep

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I have no idea what that's all about!

I told me cousin about the void...and his reply was "Whats wrong with 8 inches?"
He says he's seen similar odd situations in some older homes, but why is unknown. The outer wall seen from the outside is cut limestone. I want to see if there is another brick wythe, then the limestone and how thick that side is.

I want to look at other sections of the basement as well as how the joists and beams are set on the walls. There is a center beam that runs the length of the house, and is supported by other posts in several areas. From the way the rest of the house was built, it doesn't look like anybody was trying to cut corners, but why they did what they did with the walls is still unknown.

I like the idea of once it's all cleaned up and retuckpointed, filling the voids. Makes sense.

Thanks, guys!

vince

Bringing an older thread back to life....

I decided to wait before doing anything to the basement to see how the spring and summer rains would affect it. The house is high on the lot, with what looks like good drainage all around it and is above the water table.

Summer has passed, and several heavy rain storms have passed, including a few that flooded nearby culverts and streams. No water or flooding in the basement. So, it looks like there are no outside moisture problems, just the usual dampness of an old basement on very humid summer days.

For the walls, further investigation and excavation revealed that the walls were filled with chunks of old bricks, some old 2x4 bits, and sand. Over time the sand settled and critters tunneled into and around it.

I do wonder if the experts here have any recommendations for a non-shrink grout and the mix ratios so it is thick enough but also flows into the various nooks and crannies as I pour/scoop it in?

Thanks,

vince
Big Rock, IL