7 Pergola Design Decisions to Make Before Construction Starts

Six of the seven decisions below are locked the day the posts go into concrete. The one about what runs inside the frame is locked earlier than that, when the frame is fabricated. That short window is the whole problem with a pergola: it is a small project next to a pool or a kitchen, it gets decided quickly, and most of the regret afterwards comes from decisions nobody knew they were making.

Take them in the order below. Each one narrows the next, and running them out of order is how a pergola ends up the right size in the wrong place.

When each decision closes

Two decisions that are not on this list

Two questions come up first in almost every pergola conversation, and both are large enough to deserve their own answer rather than a paragraph here.

What it is made of. Aluminum and wood age very differently in Florida humidity, and the comparison is in aluminum versus wood pergolas over a Florida decade.

Whether it touches the house. Attached and freestanding are different structures with different post counts and different permitting, and that choice is worked through in attached versus freestanding pergola layouts.

Settle both before you start on the seven below. Everything here assumes they are already answered.

1. How big, measured from the furniture rather than the slab

The size of a pergola is not a design preference. It is the output of a furniture plan.

Decide what actually happens under it — a dining table, two loungers, a bar, a grill — and lay it out on the ground with tape before anyone draws a structure around it. Then walk it. Pull a chair back from the table the way people really do and see where your heel lands.

Two things about the numbers on a pergola drawing are worth knowing before you read one:

• The outside dimension is not the usable area. Posts sit inboard of the beam line, and the beams overhang the posts. A structure described as twelve by twenty has a smaller clear span between its posts, and that clear span is what your furniture has to fit inside. Ask for it separately.
• The shaded area is smaller than both, and it moves. A roof throws shade at an angle that changes through the afternoon. At the hours you actually use the space, part of the footprint is in sun. Which hours those are is decision three.

The structure should also be smaller than the paving under it, not the same size. A slab sized exactly to the pergola puts chair legs off the edge, and that is a mistake you notice every time somebody sits down.

2. Where the posts land

A post is the only part of a pergola that is genuinely in your way, and post positions are usually set by the structure rather than by you. That is fine, as long as you check them against how the space is used before the footings are poured.

Five places a post causes a problem, in rough order of how often it happens:

1. In the walking line between the house door and the pool or the grill.
2. Inside the swing of a slider or a French door.
3. At the edge of a pool deck, where it narrows the walkway to a squeeze. If a pool is part of this project, the features worth planning with a poolside pergola covers the rest of that overlap.
4. Centered on a window, so the view from inside the house now has a column in it permanently.
5. Where the mower and the irrigation have to get past, which is how posts end up with a permanent ring of dead grass around them.

Moving a post on a drawing costs nothing. Moving it after the footing is poured means breaking out concrete, pouring a new footing, and living with a patch in the paving.

The view from inside the house is the one people check last and regret most. Stand at the kitchen sink and the living room sofa, look out, and have somebody hold a broom where each post is going.

3. Which way the shade falls, at the hours you use it

A pergola does not shade a space. It shades part of a space, at particular hours, depending on which way its roof members run.

So the decision starts with a question about your week rather than about the structure: when will you actually be out there? Lunch on a Saturday and six o'clock on a Tuesday are different problems, and a roof optimized for one is mediocre at the other.

Three things follow from the answer:

• Roof density. Widely spaced slats read as an open frame and shade very little at midday. Tighter spacing shades more and darkens the space under it. If the hours you named are the hot middle of the day, you are probably looking for more density than the drawing shows.
• Which way the slats run. Fixed slats block sun from one direction better than the other. Running them the wrong way relative to the sun at your hours produces stripes when you wanted shade.
• What no roof can fix. Late afternoon sun comes in low and sideways, under any roof at any density. A west-facing patio at six o'clock is not a roof problem. It is a side problem, solved with planting, a privacy panel, or motorized retractable screens — and if screens are even a possibility, that has consequences in decision seven.

The cheapest way to check any of this is to stand on the spot at the hour in question, a week before the drawing is approved. Photographs of finished structures are useful for a different purpose — our project gallery shows how the same roof density reads on different houses — but they cannot tell you where your own sun is at five.

4. What the roof does when it rains

There are three families of pergola roof, and the choice between them is not really about how they look. It is about where the water goes.

An open slat roof is a sun structure, not a rain structure. That is a perfectly good thing to build, as long as you know it: a dining table under open slats is fine, and an outdoor kitchen under open slats is an outdoor kitchen in the rain. If appliances are going under this structure, see what an outdoor kitchen needs from the space around it before you settle the roof.

The moment the roof sheds water, a second decision appears that most homeowners never get asked about: where the downspout discharges. Concentrating a roof's worth of rain next to the house foundation, onto a pool deck, or at the top of a slope toward a neighbor is a worse problem than the one the roof solved. It needs a run of pipe to somewhere that can take it, and that pipe is buried — which means it happens before the paving, not after.

A solid roof also changes the structure itself. It catches wind in a way an open frame does not, which affects the frame, the footings, and what gets reviewed when the drawings are submitted. What that review involves where you live is in whether a pergola needs a permit in Florida.

5. What it stands on

A patio slab is not a foundation. It is a surface.

Pergola posts have to resist uplift, which is the load that matters for a roof in Florida, and that resistance comes from footings under the posts rather than from the slab around them. On an existing patio, the normal sequence is to saw-cut the slab at each post, dig, pour the footing, and patch. The patch is visible unless the paving can be re-laid over it.

Which gives a simple piece of sequencing that saves real money:

• If new paving is part of this project, the footings go in before the paving is laid, and the patch never exists.
• If a pool deck is being poured, the pergola footings and any sleeves for water, gas or power go in at the same time. The same logic governs the rest of that deck — see what to plan before a pool deck is poured.
• If the paving is staying, budget the cut and the patch openly rather than discovering it as a change order.

How deep and how wide the footings are is an engineering answer for your specific site and structure, not a rule of thumb, and it is one of the things a submitted drawing exists to show. A contractor who can tell you what the footings are and why is a contractor whose drawings have been through that review before.

6. What runs inside the frame

Fans, lights, a heater, speakers, an outlet, a screen motor: every one of them is wire, and on an aluminum pergola the wire runs inside the posts and beams.

That makes it a fabrication decision, not a shopping decision. The frame is cut, drilled and assembled with those runs in it. Adding them afterwards means surface conduit stuck to a finished structure, which is exactly as good as it sounds.

Two details that get missed even when the wiring is planned:

• A fan needs structure, not just power. A fan hangs off a beam and moves while it does it. The beam that carries a fan is specified differently from the beam that holds a light, and that specification happens before anything is cut.
• Circuits, not just outlets. Lights, a couple of fans, a heater and a television are not one circuit. What the panel can give this structure is worth knowing before the trench is dug, because the trench is the expensive part.

The split is the same one that governs pool equipment: you can defer the purchase, you cannot defer the buried half. Buy the fan next year if you want. Put the conduit and the blocking in this year.

7. What you are leaving room for

The last decision is about the version of this backyard that exists in three years.

Provisions are cheap while the frame is being made and expensive afterwards. The ones worth asking about:

• A column profile and header depth that will accept a screen track, whether or not screens are being bought now.
• A gas, water or drain stub to the corner where a grill or a kitchen would go.
• Conduit toward the house for a controller, a television, or lighting you have not chosen yet.
• Enough footing and frame capacity for a heavier roof, if the roof might change.

That last one is where the money is. Our estimator prices a pergola at $8,500 and a louvered roof at $18,000 as line items on a backyard project, and the arithmetic looks like it favors starting small. It usually does not, because replacing one structure with the other means paying twice for footings, permitting and installation, and the second set is more expensive than the first — it happens inside a finished yard. If a louvered roof is what you actually want, the comparison to make now rather than later is in pergola versus louvered roof.

Those estimator figures are starting configurations, not quotes, and the estimator shows every total as a range of plus or minus ten percent for exactly that reason. What moves a pergola away from its starting figure — span, roof type, footings, finish — is broken down in what changes an aluminum pergola's price. You can run your own combination through the backyard project estimator.

The order, one more time

1. Settle material and attachment first; they are separate questions.
2. Lay out the furniture. The footprint comes from it.
3. Place the posts against doors, walkways, sightlines and the mower.
4. Name the hours you will use the space, then choose orientation and roof density.
5. Decide whether the roof sheds water. If it does, decide where the water goes.
6. Put the footings in before the paving.
7. Put the wire and the blocking in before the frame is cut, and leave the provisions for later in while it is cheap.

Every one of those seven is permanent once the structure is up. None of them are expensive to get right at the drawing stage, and all of them are expensive to correct afterwards — which is the only real argument for spending an afternoon on a roll of tape and a broom handle before anything is ordered.

How we work through this sequence, and what ends up on the drawing before anything is fabricated, is on the custom aluminum pergola builders page. A project estimate starts with a site visit, because decisions two through five cannot be made from a floor plan.

Common questions

What should I decide first when planning a pergola?

The furniture layout. Size and post positions both come out of it, and both are permanent once the footings are poured. Tape the furniture plan onto the slab and stand in it before anyone draws a structure around it.

Can a pergola be built on my existing patio slab?

Usually, but the slab is not the foundation. Posts carry uplift and need footings under them, which normally means saw-cutting the slab, digging and pouring, then patching. If you are laying new paving anyway, the footings go in first and the patch never exists.

Do I have to choose fans and lights before the pergola is built?

You have to choose whether they are coming. The wiring runs inside the posts and beams, and the beam that carries a fan is not the same beam that holds a light. The fixture itself can be bought later; the conduit and the structure to hang it from cannot be added later without opening the frame.

Does a pergola need gutters?

Only if its roof sheds water rather than letting it through. An open slat roof does not. A solid or translucent roof does, and that turns into a second decision most people skip: where the downspout discharges. Next to the house foundation or onto a pool deck is worse than the problem it solved.

Should I build a pergola now and upgrade to a louvered roof later?

Only if the upgrade is genuinely years away. Our estimator prices a pergola at $8,500 and a louvered roof at $18,000, but replacing one with the other later also means paying for footings, permitting and installation a second time. If the louvered roof is the real goal, the cheaper path is usually building it once.