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A Westchester County homeowner is considering an over-roof to replace a failing, nearly flat EPDM roof and improve drainage and insulation. The homeowner’s proposed assembly aims for roughly R-60 while preserving the house’s low-profile design, but the source is a question seeking advice, not a report of approved plans or completed work.
A Westchester County, New York, homeowner is considering an insulated over-roof to replace a failing EPDM membrane, correct water ponding and improve the energy performance of a contemporary early-1970s house. The proposal targets a roof assembly near R-60 while retaining the home’s distinctive low, horizontal profile, but the account does not establish that the design has been reviewed, approved or built.
The house has a post-and-beam structure, with large glulam beams supporting tongue-and-groove 2-by-6 roof decking. The homeowner says the current EPDM covering is poorly installed, patched and near the end of its service life. The roof has little slope, and sections of drip edge along the intended drainage side are higher than the roof surface, contributing to ponding water.
The proposed work would strip the existing roof layers and cover the decking with taped 7/16-inch ZIP sheathing intended to form an air barrier. Above it, the homeowner describes 1.5 inches of Rockwool Comfortboard, a new sloped frame made with 2-by-8s, mineral-wool batts between the framing, and a further four inches of polyiso insulation beneath a new EPDM membrane. The homeowner estimates these layers would provide just under R-60, including about R-6.3 from the Comfortboard, R-30 from the batts and approximately R-23 from the polyiso.
The proposed slope is 0.5 inches per 12 inches, draining toward the back of the house. Short parapet walls on three sides would conceal the raised roof over the living space; existing overhangs would remain largely unchanged. The homeowner also proposes removing and covering existing skylights. These are design intentions and estimates in the question, not independently verified specifications.
Drainage and Insulation in One Rebuild
The proposal links two problems that often need to be addressed together during a flat-roof replacement: where water goes and how the roof controls heat flow and air leakage. Correcting the slope and drainage edge could reduce standing water, while added insulation and air sealing could improve comfort in a house the owner describes as having little existing roof insulation and very leaky original sliding doors.
For readers planning similar work, the case also highlights the trade-off between performance and appearance. Raising the roof can create space for insulation and a drainage slope, but it affects structure, roof height, parapets and interfaces with existing walls and overhangs. The homeowner’s target is not proof that the proposed assembly will perform as intended; design, moisture control and construction details require project-specific review.
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A Low-Slope Roof With Legacy Layers
The homeowner places the house in Climate Zone 4A and describes a glass-heavy design with large original sliding doors. The stated longer-term goal is to improve comfort and energy efficiency while retaining the home’s architectural character, including its exposed interior ceiling in some rooms.
The existing roof may include the original torch-down roofing beneath fiberboard and EPDM, but the homeowner says the layer history is uncertain. That matters because removing or building over existing materials can affect the condition and behavior of the assembly. The source also notes that the roof’s glulam beams span between posts and cantilever roughly four feet beyond the front and rear walls. Those details make the added framing and load a matter for structural assessment, not just an insulation choice.
Design and Site Questions Remain
The supplied source is a homeowner’s question, not an engineering report or a record of completed construction. It does not include an expert response, final drawings, permit status or a contractor’s assessment. The excerpt ends mid-sentence while the owner is discussing why tapered roof foam may not be preferred, so the full comparison of options is unavailable.
Unresolved issues include whether the existing beams, posts, connections and foundations can support the added framing and roofing; how the proposed layers will manage moisture and condensation; and how the new slope, parapets, roof membrane and drainage will be detailed. The source gives no drainage calculations, site review, product-specific assembly testing or confirmation that water can be discharged safely at the rear. The estimated R-values and the assumption that the cavity beneath the new framing needs no additional insulation are the homeowner’s, not independently established findings.
Engineering Review Before Construction
The next step described by the source is not a scheduled construction milestone. Before proceeding, the owner would need project-specific design and review, including evaluation of the roof structure, moisture-control strategy, drainage, flashing and connections to the existing house. Local building and permit requirements also need to be checked. Because this work changes a roof assembly and adds loads, a qualified building professional and structural engineer should assess the design before construction.
Further updates would be needed to establish whether the proposed assembly is revised, permitted or built, and whether its drainage and insulation targets are achieved. Until then, the over-roof remains a proposal under consideration, with its final design and performance unconfirmed.
Key Questions
What is an over-roof?
An over-roof is a new roof assembly built above an existing roof or roof deck. In this proposal, the raised framing would create room for a slope and added insulation above the home’s existing tongue-and-groove decking.
What problems is the homeowner trying to address?
The owner reports a deteriorated, poorly patched EPDM membrane, areas of ponding water and a roof with little insulation. The proposed work is intended to improve drainage, air sealing and thermal performance.
Is the roof design expected to reach R-60?
The homeowner estimates the proposed materials would bring the assembly to just under R-60. The source does not provide independent calculations or confirm that the assembly has been built or tested, so that figure remains a design estimate.
Has the over-roof been approved or constructed?
The source describes a homeowner asking about a proposed design. It does not report engineering approval, permits, construction or measured results.
What should be checked before building an over-roof?
A project-specific review should address structural capacity, moisture and condensation control, roof drainage, flashing and local code and permit requirements. A qualified building professional and structural engineer should assess the design before work begins.
Source: greenbuildingadvisor.com
