# A Frame Cabin... More roof than siding



## kikikins567 (Apr 18, 2009)

We are going to be redoing our roof in a couple of weeks, and will be doing siding later this summer.  We have struggled keeping our house insulated and our electric bills are crazy.  With the new roof, some people have suggested insulating the roof before the shingles get put on because our roof is the biggest part of our home.  First off, is this a good idea?  and if so, how would you suggest we do that?


----------



## Clayton (Apr 20, 2009)

I live in an A Frame too so I know what you are talking about.  Insulating the roof before the roofing goes on is "the best way" but also the most expensive.  I didn't do it when I built my house 40 years ago (didn't know to do it and didn't have the money either).  I wish I had, but then I live in Tennessee and we don't have the cold you do so it as not that big deal with me as it is with you. If I were you I would find a way to do it.  

The best way is to build frames of 2 x 4 and lay them on the roof; sort of like building framing walls, then you insulate between the 2 x 4s just like you would do in walls. Then you have to resheet the roof with plywood and apply the new roofing on that new plywood.  This means you have to redo all the fascia boards so it's pretty involved.

Depending on how complicated your roof design is it might be possible to prefab most the roof framing and speed up the process. The folks that build log houses with exposed wood ceilings do this all the time. Maybe you could  find a contractor that builds log homes and get an estimate on the complete job, or maybe some other ideas.

Good luck,


----------



## inspectorD (Apr 20, 2009)

You could reinsulate the top of the roof with blueboard styrofoam or Structurally insulated panels, google cold roofs or SIP construction for more info.


----------



## gpglinka (Nov 21, 2019)

I have A frame home. Screwed 2" x 4" purlins to existing roof, right on shingles. Put styrofoam in between purlins. Then covered with steel roof panels.


----------



## Jeff Handy (Nov 21, 2019)

I think if you install 2x4’s on the old roof, and totally fill the space with insulation, you will get trapped moisture and rot.

You might be better with 2x6 framing.
Lay approx 1” foam board over the old roof, between the framing.
Leave approx 1/4 inch gaps for moisture channels at the sides of the foam board.
Put unfaced 3.5 inch fiberglass over that.
Leave the resulting approx 3/4“ to 1” air space open above it.
You could also lay a channel of styrofoam soffit type rafter vents on top of the fiberglass.
Put intake vents at the bottom of the roof, and a ridge vent or another system at the top.
Put plywood and shingles over that.
The new plywood and shingles can now breathe.
And any moisture that collects above the old roof surface can trickle down and out the bottom.

Oops, just saw OP posted ten years ago, but my idea is still good!


----------



## billshack (Nov 21, 2019)

I agree with jeffy handy. you must ventilate under the plywood soffits to vent  . if not then the shingles get very hot and deteriorate very quickly.


----------



## nealtw (Nov 21, 2019)

What is on the inside. If you have drywall insulation and venting. There would be much to consider. 
Many of these houses have nothing inside and foam would be the answer with some details to consider.


----------



## mabloodhound (Nov 22, 2019)

You can by 4xx8 insulated panels (with a variety of insul. thickness) that have an air gap between the insul & top wood sheet.  These are then screwed into the old roof with long screws.  Goes up fast and then re-roof over that.  http://cornellcorporation.com/products/therm1_2.htm


----------

