Cathedral Ceiling Ice Dams Fix — Vaulted Ceiling With No Attic
Ice dams build every winter along the eave over the vaulted room, even though the rest of the roof is clear. There is no attic to crawl into, so the fix comes from inside or from the top.
A cathedral ceiling ice dams fix stops heat leaking into the roof deck over a vaulted ceiling with no attic. JMB Builders air seals the ceiling from inside where lights and seams leak, and during a reroof insulates from the roof side: vent channels with dense-pack below, or rigid foam over the deck. Across the Twin Cities and north metro, priced per project from photos.
- Priced per project
- Air sealing inside, insulation from the roof side
- Best done during a reroof
- Quote from photos in 1 business day
- Licensed MN contractor BC809005
In a vaulted or cathedral ceiling, the drywall is fastened to the rafters and the roof deck sits on top of the same rafters. The space for insulation is the depth of the rafter, and often there is no vent space above it at all. Warm air leaks up through can lights, the ridge beam, ceiling seams and fan boxes, and the insulation is too thin. The deck warms, snow melts, and the water freezes at the cold eave into an ice dam.
There is no attic to add insulation to, so there are three ways in. From inside: seal the leaks, which means airtight light fixtures or covers, sealing the ridge and wall joints, and fixing bath fans. From the roof side during a reroof: take the decking off in sections, install vent channels against the deck, fill below them with dense-pack or batts, and re-deck with a ridge and soffit vent. Or put rigid foam over the old deck, with new decking on top, so the roof never gets warm.
What does not work is filling a closed rafter bay with loose insulation and no vent path, or with foam that is too thin for Minnesota. That traps moisture against the deck. Which route fits your house depends on rafter depth, whether there are soffits to vent from, and when the roof is due. We lay that out from your photos.
What you supply
- Photos of the ice dams from outside, and of the vaulted ceiling inside with lights and fans visible
- Roof age, and whether you plan to reroof soon
- Rafter depth if you know it, or a photo of an opened fixture box or a gable end
- Any past leaks or stains on the vaulted ceiling
What JMB supplies
- Air sealing of can lights, fan boxes, ridge and wall seams from inside
- Vent channels against the deck, with soffit intake and a ridge vent
- Dense-pack or batts fitted below the vent channels
- Rigid foam over the old deck with new decking on top, when that route fits
- Ice and water membrane at the eaves and the new roofing when combined with a reroof
- Photos of the insulation before the deck goes back, in your job folder
How it is priced: per project
Quoted in writing from your photos within one business day. What moves the number:
- Air sealing only versus insulating from the roof side
- Whether the roof is being replaced anyway, which saves the tear-off cost
- Rafter depth and whether vent channels fit
- Rigid foam thickness and new decking over it
- Number of can lights, fans and penetrations to seal
- Roof pitch, height and size of the vaulted area
If a reroof is coming in the next few years, say so; the insulation from the roof side costs far less when the roof is already open.
How long it takes
Air sealing from inside: a day. Roof-side insulation on a vaulted section during a reroof adds one to three days to the roof job.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized quote within one business day. We only come out to measure first when the job needs a tape measure — no pressure, no games.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Air seal from inside
Airtight covers or fixtures at can lights, sealed fan boxes, ridge and wall seams caulked. The smallest job, and it helps every other fix work.
Vent channels and dense-pack, from the roof
Decking off in sections, vent channels against the deck from soffit to ridge, insulation filled below, and new decking and roofing on top.
Rigid foam over the deck
Foam laid over the old deck and new decking fastened through it, so the deck stays cold. Raises the roof edge, so fascia and trim are extended.
Cathedral Ceiling Ice Dams Fix — Vaulted Ceiling With No Attic: questions, answered
How do you fix ice dams on a cathedral ceiling?
Stop the heat getting to the roof deck. Seal the air leaks from inside at lights, fans and seams, and add insulation and a vent path from the roof side, usually during a reroof. Heat cables and roof rakes treat the ice, not the cause.
Why do I get ice dams over my vaulted ceiling but not the rest of the roof?
The vaulted section has only the depth of the rafters for insulation, often with no vent space above, and warm air leaks through can lights and ceiling seams straight to the deck. The rest of the house has an attic with deeper insulation and air to carry heat away. The warm deck melts snow that refreezes at the eave.
Can you insulate a vaulted ceiling with no attic?
Yes, from inside or from the top. From inside, the ceiling can be air sealed or, in a remodel, opened and filled. From the roof side, the decking comes off in sections to add vent channels and insulation, or rigid foam goes on top of the deck. The roof-side routes make the most sense when the roof is being replaced.
Can you blow insulation into a cathedral ceiling?
Only with a vent path above it or with the right kind of foam. Filling a closed rafter bay with loose insulation and no vent can trap moisture against the deck in a Minnesota winter. Dense-pack goes in below vent channels installed against the deck, which usually means working from the roof side.
Do can lights in a vaulted ceiling cause ice dams?
They are one of the biggest causes. Older can lights leak warm air straight into the rafter bay and some are not rated to touch insulation, so there is a hot, uninsulated spot above each one. Swapping to airtight, insulation-rated fixtures is done by a licensed electrician, and the bay is then sealed and insulated.
Should I fix my cathedral ceiling ice dams when I reroof?
That is the best time. The shingles are coming off anyway, so opening the deck for vent channels or adding rigid foam on top costs much less than doing it separately. Tell us when the roof is due and we plan the insulation into the reroof.
Recent JMB work, from our job log
59 installs recorded across 30 Twin Cities communities since Dec 2025. Window and door installs for homeowners and for the builders and dealers we sub for. Counts come straight from our job log; no customer names.
Get a written quote for this job
Three photos and a sentence is enough. You hear back within one business day. Or text the photos to 763-204-2099.
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Read morePage reviewed September 26, 2026 · JMB Builders LLC, MN license BC809005 · All insulation pages
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