Hello,

We have a 111-year old Victorian with a walk-up 3rd floor attic. It is currently unfinished, but does have a floor. We want to finish this space for an art studio and small bath.

The problem we're having is trying to figure out the correct way to ventilate and insulate the space. Currently, the only ventilation it has is 3 windows that I put screens in during the warm months (we live in Wisconsin).

When we finish the space, we intend to leave a fairly large space in the peak area. If we then put ventilation in the gabled ends, will that be sufficient, or do we need to do more?

Regarding insulation, we intend to insulate under the roof deck, but I'm not sure what else we need to do in regards to ventilation.

Also, the attic floor is already insulated (with blown in insulation). Is there any reason we would need or want to add additional insulation before we cover everthing with a new subfloor?

Thanks in advance for any advice!

 

You have a huge amount of design and code issues to consider before even determining if this project is feasible, and I would recommend hiring an architect before you do anything.

You may not be able to meet minimum insulation depths with any type of insulation given the current depths of your rafters and wall studs.

Unless you have vented soffits all around the house, it isn't possible to insulate and properly ventilate the rafter spaces.

Bathrooms require minimum headroom clearances which may not be attainable given the sloped roof.

The floors and joists may be acceptable structurally for minimum storage but not for use as habitable space.

Best place to begin here is with a local architect or other design professional.

 

Since you live in the republic of Wisconsin you would be wise to talk to your local building official.

Wisconsin now has the same code as many other states, but there are some additional requirements and often the interpretation of the requirements is different due to differences in climate and other items when you are dealing with insulation and moisture control.

You may have a few problems with a new bath on the 3rd floor.

You will have to satisfy the local inspector, so you should talk to him now instead of later.

Good luck with your Victorian!!!

Dick

 

Regarding the insulation depths, we are planning to add firring strips to bring out the rafters and studs enough to put in insulation with an R value high enough (at least R19 or higher).

I find it hard to believe that the only way to get enough ventilation is to add vented soffits. Depending on how we insulate under the roof, we may only end up with a small portion of the roof deck actually insulated (because of the knee walls and peak).

The entire 3rd floor has very tall ceilings and we will have more than adequate headroom for a bathroom. The center of the room (from the floor to the peak is at least 15' high). This is a very tall Victorian home. Actually, at one point, one portion of the attic was completed as living space (with plaster and lighting).

Regarding the floors, we know that the floor joists are the same size as the rest of the house. We intend to put a new subfloor over the existing floorboards.

Really, our biggest issue is trying to figure out how to ventilate properly without tearing up half the house.

 

Thanks for the quick reply Dick. Actually, we live in a very small community along the Mississippi (just across the river from your state). They don't even have a local inspector - basically they review what your building permit says and make sure it isn't out of line. No inspections at all.

Like I stated to the previous post, our main issue is determining how to correctly get enough ventilation without ripping up half our house. (We already are going to be lifting it off the foundation this year and replacing the foundation).

 

You will either have to install perforated soffits or ventilate the 'attic' spaces behind your knee walls with gable vents to give you enough air flow up and through each rafter space.

In addition, each rafter bay will need to have rafter vents installed that either run from the perforated soffits or from the 'attics' behind the knee walls up to the 'attic' at the top of your cathedral ceiling.

There must be air flow into to rafter spaces that equals the air flow up-through-and out of the vented cathedral ceiling attic either via ridge, roof, gable, or other type of venting.

But the point is that you need to get ventilation air into each rafter space and that needs to come either from perforated soffits all around the house or gable type vents in the spaces behind the knee walls.

Without knowing the precise layout of your attic, it is impossible to say just HOW yours needs to be accomplished.

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By the way, Wisconsin has not yet come on board with the rest of the US as a far as Codes are concerned and still uses its own unique brand of Codes for building.

Best to contact your local code office for details as has been already stated, but you can find Wisconsin code here:

http://www.legis.state.wi.us/rsb/code/comm/comm020.html

 

Thanks for the reply Manhattan...

After taking another look at our house, I think we'll be able to put in soffit vents without too much of a headache (except for the height - our roof is 3 floors up)...

I hadn't thought of gable venting into the attic-type area behind the knee walls. That might be a possible solution, depending on how it looks from the outside.

We do want to get the ventilation correct, otherwise that 3rd floor attic will be extremely hot (and lead to LOTS of other problems)...

Thanks for the link on the state of WI codes - I'll check them out...