Can my existing flat roof take the extra weight?
Roof area alone cannot answer this. Ask the solar designer to identify the proposed array, mounting positions and loads, then arrange a competent assessment of the existing construction. A garage, extension and commercial roof may have very different supporting structures.
K2 Systems' load-distribution guidance highlights additional loads on the supporting structure, insulation and roof covering, including changed snow-load distribution. Insulation beneath a sound-looking membrane also needs assessment; the visible surface is only one layer.
Ballasted or mechanically fixed: what changes?
A ballasted system uses designed weights to restrain the array. It avoids some penetrations but adds weight; the ballast layout must come from the selected system's project design. Do not use a guessed number of paving slabs. K2 warns that specifying stones by quantity can result in over-ballasting.
An anchored design introduces roof connections which need coordinated structural fixing and waterproofing details. Ask who designs and installs those interfaces and who accepts responsibility for leaks. The appropriate option depends on the building and selected system.
Should the roof be renewed first?
Record existing leaks, patch repairs, ponding and known roof age before a quotation is agreed. Ask a roofer to explain what can be inspected without opening the build-up and what remains unknown. Installing equipment over a roof already needing substantial repair can make the later work harder to organise.
Compare two written scopes where relevant: roof work followed by solar, and solar on the retained roof. Include access, removal and reinstatement responsibilities if later roofing work is needed. Do not assume a solar warranty covers the roof or a roofing guarantee covers the mounting installation.
What should I send for a roofing assessment?
- Property postcode and whether the roof is a garage, extension or main building
- Existing roof specification, installation date and guarantee if available
- Ground-level photographs, any internal stains and a description of previous repairs
- The solar installer's proposed layout, mounting system and load information
- A request to agree drainage access, membrane protection, maintenance access and warranty responsibilities
What your quotation should confirm
- Condition and limitations of the existing roof survey
- Structural assessment and project-specific mounting design
- Compatibility of insulation, roof covering and support pads
- Waterproofing responsibility at any penetrations
- Any roof repairs priced separately from solar equipment
- Access and future removal/reinstatement responsibilities
Useful primary sources
These links provide regulatory, trade-body or manufacturer information. Product guidance does not replace a property-specific specification.
What to check next
- Confirm structural capacity
- Avoid blocking drainage routes
- Coordinate penetrations with the roofing system provider
When should you ask a roofer to inspect it?
Arrange a survey for recurring leaks, soft or deflected decking, persistent ponding, split details, blistering or an unknown build-up. Openings may be needed before anyone can responsibly confirm whether an overlay is suitable or the roof must be stripped.
Safety first: do not climb onto a roof without suitable access, training and protection. Keep clear of loose coverings, unstable ceilings and water near electrical fittings.
Would you like a property-specific answer?
Request an inspection and written quotation from J&L Welch.
No deposit is required. Payment is due on completion within seven days, with the agreed scope and price confirmed in writing.