Designing with Grillo Panels

Most people come to a veranda thinking about the roof, reasonably enough — it is the expensive part and the part that keeps the rain off. Once the roof is settled, the conversation moves sideways to the two ends. Leave them open and the space still catches low afternoon sun down its length and gives the neighbours a clear view of your dining table. Close them in glass and you have something closer to a room, with the cost and loss of airflow that implies. The slatted panel sits between those positions, and answers more questions than most homeowners expect.

Grillo panels are modular aluminium slatted click panels, and they are among the components we find ourselves suggesting most often at Roma Verandas once we understand how a garden is actually used rather than how it looks in a photograph. This guide explains what the panel is, how slats behave differently from glass or solid infill in light, privacy and wind, the jobs they can do beyond closing off a side, and where they are the wrong answer.

What a Grillo Panel Actually Is

The panel is a framed run of aluminium slats. The blades click into an outer frame drawn from the same profile family as the veranda itself, powder coated in the same colours and gloss levels, and the assembly is rigid and self-supporting rather than something needing a fence post at each end. It is modular too: an opening is filled by repeating a standard unit rather than fabricating a one-off. That distinction matters. A timber trellis has to be attached to something structural; a panel of this kind is a system component, sized to the opening between two posts or between a post and the house wall, and fixed into the frame much as a glass side element would be.

Because it is powder-coated aluminium rather than timber, it does not move seasonally, need treating, or grey and warp the way slatted timber does after three or four winters. The blades are a consistent profile at regular spacing, so the effect reads as a deliberate architectural element rather than fencing. Panels can fill an opening completely or sit as a partial infill above something else, and much of their usefulness comes from that second option.

Light, Privacy, Wind and Airflow

The behaviour worth understanding is how a slatted panel handles a sightline. Seen square on you look through the gaps at whatever lies beyond. Seen from an angle — which is how almost everybody sees a garden screen — the blades overlap visually and the panel reads as solid. That is why slats give real privacy from a neighbouring garden or an upstairs window without the shut-in feeling of a solid infill: the people you are screening from look obliquely, while you look through it from much closer and squarely on.

Light follows the same logic. A solid aluminium infill panel at the end of a veranda casts a hard shadow and darkens that end, particularly on a west or east elevation where low sun would otherwise run in along the length of the structure. Obscure glass keeps the light but gives a bright, blank surface and no air movement. Slats let some daylight through and break the rest into bands that move through the day, which in a space meant to feel like part of the garden is the more comfortable result.

There is an assumption that a solid panel must be the more robust choice because there is more of it. Structurally the opposite is often true. A solid side element two metres wide and two and a half metres tall is, in engineering terms, a sail: in a gust it passes the full pressure of the wind into the post, the base plate and the foundation beneath. A slatted panel lets some air through and spills the rest, so the peak pressure across it is lower. That does not make wind loading irrelevant, but it does make slats the more sensible choice on an exposed plot.

Ventilation is the other consequence, and the one people notice in the first warm week of the year. A veranda closed on three sides under a glass roof becomes a greenhouse quickly; warm air has nowhere to go, and the space is least usable in exactly the weather you built it for. Slatted panels keep air moving at low level, which makes a genuine difference in July.

The Jobs a Slatted Panel Can Do

Used as a side element the panel is straightforward. The more interesting uses come from treating it as a component you can put anywhere. A common and effective arrangement is a partial infill: a glazed panel at the lower level, so the view from a seated position is unobstructed and the wind is kept off your ankles, with slats above to break the sightline from a neighbouring first-floor window. You get the view where you want it and privacy where you need it, and the division reads as intentional.

On their own posts, away from the structure, the same panels work as garden screening — dividing a seating area from the working end of a garden, enclosing a hot tub, hiding bins or plant, or forming a short run of boundary screen where a close-boarded fence would look too heavy. Around equipment be precise: an air source heat pump needs a specified clear airflow zone, and those clearances are not negotiable. They also make good climbing plant supports, with nothing behind the plant to rot as timber does — though a mature evergreen turns a porous screen into a nearly solid one, which changes the loading the posts see. Say so at survey stage rather than three summers later.

Colour, Alignment and Getting the Look Right

Three things separate a slatted screen that looks designed from one that looks bolted on. The first is colour. Panels should match the veranda frame exactly — the same RAL reference and gloss level, not an approximate grey. Anthracite, RAL 7016, is the most common UK choice, and suits slats because a matt or fine-texture finish absorbs light along each blade rather than throwing a highlight off every edge.

The second is slat direction. Blades running horizontally emphasise the width of an elevation, read as calm against the horizontal lines of a veranda beam, and screen a level sightline from next door particularly well. Running them vertically lifts a low structure and suits a tall, narrow opening, but it draws the eye upward and sits less comfortably beside a run of glass. Keep one direction across a whole elevation rather than mixing.

The third is alignment and rhythm. Mixing slatted panels with glass, the vertical divisions want to line up: consistent module widths across the elevation, and any transom at the same height in every bay. Where a slatted panel sits above a glazed one, that junction should relate to something else on the structure rather than landing at an arbitrary height. Settle this at mood board stage, because post positions follow the module layout. Photograph the elevation from the positions you actually sit in, mark where the sightlines matter, and work the panel positions out from that.

Where Slats Are the Wrong Answer

Slats are not weather protection, and it is worth being plain about that. Rain driven at an angle comes through, and on an exposed elevation in a westerly it arrives with enough energy to wet the floor a metre or more in from the panel. Leaves and fine snow blow through. If you want genuine shelter at that end — somewhere to sit on a wet February afternoon — the answer is glass, sliding side elements or a zip screen. They do little for noise either, whatever they do for the view.

Proportion matters too. On a narrow veranda of, say, two and a half metres projection, a full-height slatted end on both sides can make the space feel like a corridor even though the panels are visually light. One screened side and one open side is often better, and that judgement is easier standing in the garden than looking at a plan.

Deciding Where They Go

Slatted panels are among the few elements of a veranda that are genuinely flexible in use, which is why they repay being thought about early. Working out at design stage where privacy is needed, where the wind comes from and where the view should stay open tends to produce a layout that needs fewer panels than people assume, and looks better for it.

We would rather walk the garden with you and establish which sightlines genuinely bother you than specify screening on every elevation as a matter of course. Some customers find one well-placed panel does the whole job; others want a full run and are right to. Either is reasonable, but it is a far better decision to make while the structure is still on paper, and worth talking through before anything is manufactured.