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Question DetailsAsked on 10/10/2015

Can insulation be added to top of roof in 1940's 400 sq ft pool house that has beam and board ceiling?

We bought a house that has a permitted 1940's 440 sq ft pool house. Somewhere in the 1970's and again around 2000, previous owners framed in part of the porch across the front adding more square footage but giving it a slump roof look on the front. Both flat sides of the pool house are just over 6 feet and the peak in the middle is about 9 feet.
Just beam and board ceiling; no insulation. Gets like an oven in the summer and an icebox in the winter.
Too costly to raise the roof to add insulation, but not enough space to add a drop ceiling with insulation. Is it possible to take off the shingles and add insulation etc to the top of the roof? No insulation in the walls either but it's the roof that carries the heat. You can smell hot wood when you walk in if the wall a/c isn't on. Ceiling so low, nowhere for the heat to go.

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2 Answers


If you remove old shingles to add a dense high R value insulation you will in affect be also reroofing. If you are NOT in love with interior underside look, here are two choices.

1)Cellulose insulation mixed with glue can be spray applied to ceiling. With both ceiling can be covered with drywall or chip board for fire safety.

2)Spray foam insulation (by company that does new construction) can be applied.

You can also use a foam company that specializes in remodeling to insulate side walls or remove exterior siding and drill and blow cellulose in existing cavity. I suggest you explore your choices.

Jim Casper Guy who has worked home shows next to spray foam companies and old energy guru.

ps for ideas on gutters and gutter covers see my blogs

Source: www.heartlandmastershield,com

Answered 4 years ago by jccasper


I would not go with cellulose - especially if your area gets cold in the winter, because you might get condensation up at the underside of the roof and cellulose holds moisture and can support mold too.

As JC said - spray foam on the underside of the roof is an option (the more expensive closed-cell would be better as it limits interior moisture flow into the roof the best), sealed from the living space with fire-rated drywall ceiling - though you lose the exposed rafters doing that. Putting foam under the sheathing makes for a hotter roof, which can result in shorted asphalt and wood single life, and also seals-in the roof sheathing so any leaks in the roof, instead of possibly (unless large) drying out on the underside of the sheathing (planking in your case) will cause mold and rot, so the life of the sheathing is likely to be decresed, at least locally, by any roofing leaks through the water barrier.

Rigid foam board over the roofing sheathing, then water barrier over that, then shingles or metal roofing also works to some exteant, but with a couple of major issues. Generally, because of the difficulties with fasteners in foam board, it is easier to put metal roofing over it then regular shingles because using 6-10 inch shingle nails to get through the sheathing for holding power is expensive and requires hand nailing. OR, you have to put nailing strips (usually 1x3) for the shingles, so as say 5" spacing. The problem is foam board (expanded polystyrewne like Dow HI-40 say) is a vapor retarder or vapor barrier, depending on how sealed at the joints. This means any moisture getting to it form the inside will condense at its surface, causing rot in the sheathing planks. Likewsie, because it cannot promote wicking from the back of the shingles, they will stay wet after windy rain events or any leaks or backup from ice damming, also causing detearioration of the back of the shingles - especially if wood, which needs to breathe to avoid decay.

So - darned if you do, darned if you don't - but if you do it, I think I would go with an exterior foam board application if you had to choose, and at least if wood shingles-shakes provide a ventilation space between them and the tarpaper with nailing battens.

Other possibly cheaper solution that would prolong the roof life - especially if this pool house if not in constant use - air conditioning or swamp cooler combined with ceiling fans to mix the air, and additional heating for winter. Of course, if constantly inhabited, that gets expensive.

Answered 4 years ago by LCD

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