Ceiling cracks & bulging plaster on walls

[Mary7]

Hello,

We recently bought a 60 years old house. The house seems in a great shape, but since the temperature started going down, a number of cracks have showed up and the plaster on some of the walls is bulging. I am quite a newbie with this and must now turn to the wisdom of the internet for help.

A large crack has appeared in our bedroom ceiling over the last 2-3 weeks. One side of the ceiling appears to be going down, and the difference between both sides of the crack is almost 2 mm at the widest (IMG_1254). The crack is still spreading.

There are also small ceiling cracks in other rooms, but this one is the worst. The cracks only appear on the second floor ceiling (below the attic). The ceiling has been fixed in other rooms. Our home inspector mentioned that was normal in this type of older houses as the attic wasn’t initially isolated. As the previous owners isolated the attic, I had hoped this would take care of the cracks for good – apparently not!

Another problem we have is that the plaster walls on the second floor have been bulging slightly along a sort of brick pattern. Horizontal lines are the most obvious and are ~18 in. apart.

The bulging is mostly present on inside walls and on the outside wall of the room with the ceiling crack. It is not severe enough that I can break the plaster if I push on it, but it is unsightly.

What can be causing this and how can we address the sources of the problems?
Could attic aeration and humidity contribute to these problems? Our home inspector pointed out that our neighbour’s house had a type of metal screen that allowed air to go in and out of the attic, which we do not have. There are 5 air traps on our roof, but he said it would only allow air to go out, not in.

As for humidity, there is no fan in the bathroom (only a hole in the ceiling going to the attic). There are 2 windows, but I cannot really leave them open in winter. Installing extra heating and leaving the door open have helping preventing condensation, but might cause problems elsewhere.

Also, as the outside temperatures keep dropping, is there an ideal indoor temperature and level of humidity to minimize such damage?

My apologies for the long-winded description. And thank you very much in advance.


Mary

[pushkins]

Hi Mary, welcome to the site.
There can be numerous reasons for what your seeing, so I'll try to outline a couple and possibly narrow the field.
Cracks in plaster will often show up much more in winter when furnaces kick in, what actually happens is in the process of heating, moisture is drawn out of everything in the house, from walls to furniture even from us (evident by most people seeing dry skin in winter months), as the moisture is drawn out the material contracts thus cracking or showing existing cracks. Many people will actually add moisture during winter months for example with humidifiers or simply boiling water on a stove.
Moisture from the bathroom doesn't really count as it tends to be way too much in way to small a place.
If the attic was once not insulated then it is very possible that the cracks have been there for years and become more obvious in winter months as mentioned above, once plaster cracks, it's cracked and while it can be repaired, many times the repairs are fairly short term before the cracks show up again.
Another area to look at is I noticed you mentioned about a bathroom without an exhaust fan, as well as a hole allowing warm moist air into the attic this too is a big no no as well as allowing cold air from the attic to drop into the bathroom. Excessive moisture getting into an attic space causes all sorts of problems in the attic as well as possible damage to plaster ceilings.

It would be a good idea if you can get hold of a moisture meter and test the areas where the plaster is bulging, damp brick walls will often make plaster start to loosen, same for ceilings although usually in situations with water involved you will see water marks/staining. moisture meters are available at Lowe's/HD are are pretty cheap at around $10.

You do need to address the issue of soffit vents, like you mentioned you have roof vents but for these to work they NEED lower vents to suck air in from, most often these vents are in the soffit area as this allows air to be pulled into your attic from low and exit out through the top creating a good airflow. In fact it doesn't matter how many vents you have on top of your roof if they have no place to draw air from it creates a negative void meaning that it's like sucking on a straw and covering the other end with your finger.

Have you checked in your attic for any roof leaks ? this can also be a big problem for plaster ceilings and walls, the smallest of leaks are sometimes insidious enough to not leave water stains but enough to loosen plaster.

[Mary7]

Hi pushkins,

Thank you very much for your advice. I haven’t managed to get a moisture meter, but I got a humidity meter and the humidity level in the house is definitely too high (around 55%). I will try temporary solutions (geting rid of plants and opening windows) until we can get a bathroom fan and soffit vents installed. The roof is new (2007), but I will check it just in case. I cross my fingers that there is no leak...



Thanks again!
Mary