Roof structural check for solar panels and plant
A check that an existing roof can safely carry solar panels, plant, or a green roof, with strengthening designed if it can't.
About this service
Solar panels, battery enclosures, air source heat pumps and green roofs all add load to a roof that was not designed with them in mind. Panels themselves are fairly light, but racking, ballast on flat roofs and wind uplift can change the picture considerably. A heat pump on a flat roof is a concentrated load that also vibrates. Our roof load assessment checks whether the existing structure can take the new equipment safely before it is fixed in place.
We work for homeowners, installers, landlords and managing agents of small blocks. Installers often need an engineer's letter before they proceed, and Building Control may ask for one where the roof structure is affected. Pitched roofs on terraced and semi-detached houses are usually a quick check. Flat roofs on mixed-use buildings, especially with ballasted systems or green and blue roofs, take more work.
If the roof is adequate, you receive a concise letter confirming it. If it is not, we design fixings or strengthening so the project can go ahead, and larger repairs move into roof strengthening design. As with all our design work, calculations pass through three-step quality control with final sign-off by our Head of Engineering. Fees start from £300 + VAT.
When you need it
- You're installing solar PV or a battery system on a roof
- New air source heat pumps or plant are going on a roof
- You're adding a green or blue roof
What's included
- Review of the existing roof structure
- Load calculations for the new equipment, wind and snow
- Fixing and strengthening design if needed
How it works
- Gather equipment detailsWe need the layout, panel or unit weights, mounting system and ballast details from your installer. For green or blue roofs, the saturated build-up and any stored water depth matter most.
- Survey the roof structureWe inspect the roof from the loft or ceiling void where possible, recording rafter or joist sizes, spacing, spans and condition, and check how loads reach the walls below.
- Calculate the loadsWe combine the weight of the equipment with snow and wind loads for the site using Eurocode methods, including uplift at panel edges and corners, which often governs the fixings.
- Report or design strengtheningWe issue a letter or report confirming adequacy, or set out fixing and strengthening design with drawings. Where Building Control is involved, we send them the documents.
What you receive
Ballasted systems, wind uplift and green roofs on flat roofs
On a flat roof, panels are often held down by concrete ballast blocks rather than fixed through the membrane. That avoids penetrations but adds a lot of dead weight, sometimes concentrated along rails. Timber flat roofs over rear extensions and back additions were rarely designed for this. Wind matters too: ballast must stop panels lifting at roof edges and corners, where suction is highest. Similar issues arise with roof terraces on flat roofs.
Green roofs are heavier still once soaked, and blue roofs deliberately hold rainwater for a period after a storm. Both need a careful structural check and a sound waterproofing build-up. Where a green or blue roof forms part of a planning drainage requirement, our SuDS strategy work and this assessment can be coordinated so the roof meets both.
Frequently asked questions
Do I need a structural engineer for solar panels?
For a standard pitched roof in good condition, installers can often proceed on manufacturer guidance, but many ask for an engineer's check, and it is sensible where the roof is old, sagging or has been altered. Flat roofs, ballasted systems and larger arrays generally need a structural assessment. Building Control will confirm whether one is required for your installation.
Can my roof take the weight of solar panels?
Most sound pitched roofs can, because panels and rails add a modest load compared with the roof covering. Problems arise with undersized or damaged rafters, removed purlin struts, and flat roofs carrying ballast. A roof load assessment confirms capacity for your roof and your equipment, and designs strengthening if it falls short.
Can an air source heat pump go on a flat roof?
Often yes, but the unit is a concentrated, vibrating load, and timber flat roof joists may need a frame or platform to spread it onto walls or beams. Access for maintenance, noise and planning rules also need thought. We check the roof and design a support frame where one is needed.
What does a roof load assessment include?
A review of the existing roof structure, load calculations covering the new equipment, snow and wind, and fixing or strengthening design if the roof falls short. You receive a letter or report suitable for your installer and Building Control. Our typical turnaround is 10 working days, confirmed in writing with the fee.