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Question DetailsAsked on 7/3/2014

What would be a ballpark figure for the cost of widening the dormer in the back of a Cape Cod to widen the bathroom

Looking at a house to purchase and don't like the narrow bathroom that's squeezed into the existing dormer. It would be fine with an extra 2-3 feet of width and an updated bathroom. Just trying to understand if this is something that I could afford to do so I can factor it into what I'm prepared to offer for the house. Looks like the original bathroom. House is 58 years old.

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2 Answers


Without a bunch of photos it would be very tough to provide any accurate estimate. You could be looking at $19K - 30K.

Unless you can get this propery CHEAP, you are better off just buying something else. That could be a really major revenovation and major PITA.

Good luck!


Answered 6 years ago by Jefferson


I am going to presume the $19-30,000 number jefferson gave you is for widening the dormer AND upgrading the bathroom, because you can totally replace your whole roof structure and roofing for something typically in the lower end of that range or even less, so that amount does not make sense for just a dormer widening.

For the expansion of the dormer only - depends on your roof and supporting system of course, but I have seen it done for in the $4-8000 range, assuming your current dormer is not too wide already so you are not carrying a majority of the roof. Easier with rafters than roof trusses generally, and easier if you have an intermediate load bearing wall midway across the house that can support new floor joists - assuming the floor joists run in the same direction as the dormer does. Basically, , preferably on only one side of the existing dormer (typically gain 22-1/2 to 24" per rafter taken out) and bring the roof load for everything on those rafters being cut and now stopping at the dormer bumpout down onto a wall - presumably the bathroom entrance door wall. That wall then is carried on new or beefed-up (doubled or tripled) floor joists bearing on the outer wall, passing under the bathroom, and supported at the other end on the mid-attic bearing wall, or in worst case all the way across to other wall. Easiest case is if was built with bathroom in the floor plan, so a load bearing wall exists on the lower floors right under the bathroom wall furthest into the attic - presumably the doorway wall.

That $ amount does NOT include replacing flooring disturbed to put in the new joists or any bathroom construction costs other than roughed in new bumped-out wall, plus modified completed (structural and roofing) dormer.

If attic floor joists run the other way (cross-ways to the dormer ridgeline, can be a REAL problem - doable, but typically requires carrying load-bearing columns down through the attic floor all the way down piers penetrating the house slab, or modifying the roof system all the way across the roof at the dormer location to transfer the roof load away from that area, which also means opening up a good chunk of roof to the weather and requiring protection against the elements for at least several days at a minimum - and could drive costs up substantially.

Since you are looking at cost as part of a buy offer, you need a good detailed estimate for this - which would call for an architect or general contractor to do a takeoff and moderately detailed estimate, to which you should attach a 20-25% contingency.

Answered 6 years ago by LCD

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