Old Homes without Vents

Hello All,
I live in a part of the country with many old homes. I am noticing that some of them don't have vents or the vents are not done well.
My Question: If a person was to be renovating a bathroom or designing a new one for a home like this and had to run a new vent where is it best to run the vent? Many of these homes have very narrow exterior walls (more narrow than even 2X4 framing. Also if you were to go up an exterior wall (not on the gable end of a home) and cut almost a complete section out of the top plate of a wall, how much does that weaken the top plate, could that eventually cause sagging of the roof? Just wondering about retrofitting vents on existing old homes.

Thanks,
Molo

I had never seen a house without a vent until we got this one, and the only option I could see was to run it up (from the basement) in a corner through the floors (1st and 2nd) where the center wall of the house meets the back wall. We got this place with a complete remodel in mind, and a bedroom closet on the first floor and the wall at the end of the shower/tub on the second will eventually hide the new drain and vent lines.

plate

The studs beneath the top plate are holding the roof up. The double plate just holds them together and provides something for the roof joists to set on. If cutting a piece out does anything bad, it would be the the double could crack there and the wall bow out, or in, but since the roof joists are fastened to it, they then hold it in place. So to answer your question, cutting, or drilling a section has little practical effect on the structure.

A recent remodel I did gave me the same headache. I used a door knob hole saw to go thru the top plate and straight thru the roof where I ran a 1 1/2" pvc vent pipe. Other places I have run up thru closets and have installed second walls in inconspicuous places like closets to hide the pipes. Another option is to use air admittance valves to avoid the venting problems.

Can you also add a dryer vent to this new bathroom vent?

We recently acquired a small cottage that has two bathrooms without vents. There is also a washer/dryer, with a creative, but ineffective dryer vent that has a vent hose directed to a water bucket in the furnace room! The clothes dry in the dryer, but moisture goes back into the house! When we remodel our bathrooms, and add the exhaust fans, can we also tie in an exhaust for the dryer?

You don't want to pipe the dryer vent into the plumbng vent...lint can build up and cause lots of problems in the plumbing. Someone will give you a better and more complete answer. I would definitely pipe it to the outside but may incorporate a lint catcher in it some way depending on whether it goes up or down and how far away it is from an outside wall.

You will be much better served to keep the bathroom exhaust vents and the dryer vent separate. Adding check valves in the vents is not reliable, and you'd end up directing not only the moisture, but the lint back into the bathrooms. You also want to keep the dryer exhaust run as short as possible to prevent condensation which can leak out and damage things.

Now, there are systems that will allow you to vent more than one location (bathrooms, kitchen,etc.) with one fan motor which is nice. The motor is remote, so it is very quiet.