The slab that is too hot in July and too slow to dry in November

Buy nothing yetMove the table before you buy the pergola.

Before you buy a pergola, move the table.

Every change below is put into the plan and the whole model is run again. That is why a pergola's winter cost shows up here without anybody having written it down, and why the cheapest thing that actually buys hours back is allowed to win.

Fixing

For

Reading at

11:00 AM·October

In the sun. The sun is 24° up.

Where it stands now

Crossing it barefoot

Barefoot crossing works for crossing barefoot at this hour.

“Works” means the model's weighted checks support this use, and no reading is past its own limit. A reading listed as close still needs attention; it does not mean every reading passed.

Close to the limit Direct sun is 100 / 100 — 15 over (at most 85)Worked out: Computed from the geometry, the sun and the weather you gave it.
Direct sun is on this spot right now.
Sun on the crossing is only a problem because of what it has done to the slab for the last four hours.

What would change this. This would change if direct sun moved. A reversible test is how you find out whether the model named the right mechanism.

Confidence low (37%). Treat this as a starting hypothesis, not an answer.

What this answer was built from

Use: Crossing it barefoot
Place: Barefoot crossing
Weather: Temperate maritime, mild, grey, damp (scenario shape), scenario (from a published source)
Method: Traced geometry and radiation at this hour, measured against what this use needs

The smallest thing that helps at this hour

A 6 ft 11 in panel to the south-east

A 6 ft 11 in panel to the south-east fixes direct sun.

Summer solstice, 21 June: still 7 hours usable.

Winter solstice, 21 December: still 7 hours usable.

No extra hours this daya project

Nothing on the list buys extra hours on this day, so this is the least effort that still moves a limit.

Not offered, and why

Glare is not what is limiting this seat, so turning it changes very little.
No observer is marked, so there is no sightline to interrupt yet.
No observer is marked to screen from.
Wind is not the limiting factor at this spot, so a windbreak solves a problem you do not have.
Every fixture here is already fully shielded.
Nothing overhead here to hang a curtain from yet.
Nothing here is low enough for a step up to see over.
There is no boundary here to build on.
No observer is marked to screen from.
No observer is marked to screen from.
No observer is marked to screen from.
Wind is not what is limiting this spot.
Wind is not what is limiting this spot.
Wind is not what is limiting this spot.
Wind is not what is limiting this spot.
This point is a place for people, not a place for a plant.
Every fixture here is already warm.
There is no lighting here to rearrange.

22 changes, tested at 11:00 AM in October

One at a time, so you can tell what caused whatLook at the plan

Does it have to suit you?

All 22 changes, in the order the engine ranked them. Say something about your situation and the ones that would not suit you get set aside.

I rent, so nothing permanentRules out anything that cannot be taken away again.
Nothing that needs a builderRules out changes that need footings, trades or a structure fixing to the house.
I want it working this seasonRules out planting and anything else that only works once it has grown.
I will not maintain itRules out anything needing regular watering, pruning or seasonal putting away.

TestA projectYou can undo it

A 6 ft 11 in panel to the south-east

ForecastWorksstill Works

A 6 ft 11 in panel to the south-east fixes direct sun.

A solid panel about 6 feet 11 inches high and 9 feet 10 inches wide, standing 7 feet 3 inches to the south-east. Low sun arrives almost horizontally, and only something vertical stops it.

Gained: Direct sun
Lost: Nothing here.
Unchanged: Nothing here.
Still unanswered: Nothing here.

The test: A 6 ft 11 in panel to the south-east
If it worked: direct sun no longer stops the hour.
If it didn’t: If the hour feels the same after you try it, the model guessed at the wrong thing.
Next evidence: Measure the actual height available before ordering: this is sized at 6 feet 11 inches and about four inches either way changes whether it works.

+0 hours of usable time on this day. Opens 11:00 AM to 6:00 PM.

Summer solstice, 21 June: still 7 hours usable.

Winter solstice, 21 December: still 7 hours usable.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

Summer beam up about 0 per cent, winter beam down about 92 per cent at this hour.

CommitmentA projectPermanentYears to work

A deciduous tree 23 ft south-east of the seat

ForecastWorksstill Works

A deciduous tree 23 ft south-east of the seat fixes direct sun.

A medium deciduous tree planted 23 feet to the south-east, grown to about 26 feet, with a crown roughly 19 feet 8 inches across.

Gained: Direct sun
Lost: Nothing here.
Unchanged: Nothing here.
Still unanswered: Nothing here.

The test: A deciduous tree 23 ft south-east of the seat
If it worked: direct sun no longer stops the hour.
If it didn’t: If the hour feels the same after you try it, the model guessed at the wrong thing.
Next evidence: Measure the actual height available before ordering: this is sized at 26 feet and about four inches either way changes whether it works.

+0 hours of usable time on this day. Opens 11:00 AM to 6:00 PM.

Summer solstice, 21 June: still 7 hours usable.

Winter solstice, 21 December: still 7 hours usable.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

It does not meaningfully change the beam in either season.

CommitmentA projectPermanentYears to work

An evergreen group behind the deciduous planting

ForecastWorksstill Works

An evergreen group behind the deciduous planting fixes direct sun.

A group of evergreens to about 8 feet 6 inches set behind Dense deciduous tree. In summer it disappears into what is already there; in February it is the only thing standing between the seat and the view in.

Gained: Direct sun
Lost: Nothing here.
Unchanged: Nothing here.
Still unanswered: Nothing here.

The test: An evergreen group behind the deciduous planting
If it worked: direct sun no longer stops the hour.
If it didn’t: If the hour feels the same after you try it, the model guessed at the wrong thing.
Next evidence: Measure the actual height available before ordering: this is sized at 8 feet 6 inches and about four inches either way changes whether it works.

+0 hours of usable time on this day. Opens 11:00 AM to 6:00 PM.

Summer solstice, 21 June: still 7 hours usable.

Winter solstice, 21 December: still 7 hours usable.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

Summer beam up about 0 per cent, winter beam down about 85 per cent at this hour.

TestMove itYou can undo it

Move the table 6 ft 7 in north-west

ForecastWorksstill Works

Move the table 6 ft 7 in north-west does not move this in any way worth the effort.

Slide the seating about 6 feet 7 inches toward the north-west and change nothing else.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Move the table 6 ft 7 in north-west
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Mark 6 feet 7 inches out on the ground and stand there before committing. The geometry is only as good as that distance.

+0 hours of usable time on this day. Opens 11:00 AM to 6:00 PM.

Summer solstice, 21 June: still 7 hours usable.

Winter solstice, 21 December: still 7 hours usable.

Solstice hours are how long this use can happen on those days. The beam sentence is one clock time, and a different number.

It does not meaningfully change the beam in either season.

TestMove itYou can undo it

A second seat 19 ft 8 in north-east

ForecastWorksstill Works

A second seat 19 ft 8 in north-east does not move this in any way worth the effort.

Put two chairs 19 feet 8 inches to the north-east and leave the main table where it is. The point is not to fix this spot but to stop needing it at the hour it does not work.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: A second seat 19 ft 8 in north-east
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Mark 19 feet 8 inches out on the ground and stand there before committing. The geometry is only as good as that distance.

It does not meaningfully change the beam in either season.

TestMove itYou can undo it

Sit under Dense deciduous tree

ForecastWorksstill Works

Sit under Dense deciduous tree does not move this in any way worth the effort.

Move the seating under Dense deciduous tree, which is already standing and already casting something. Costs nothing and takes an afternoon of trying it.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Sit under Dense deciduous tree
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Try it on the plan, then go outside and see.

It does not meaningfully change the beam in either season.

TestMove itYou can undo it

Two 8 ft 2 in parasols instead of one

ForecastWorksstill Works

Two 8 ft 2 in parasols instead of one does not move this in any way worth the effort.

Two parasols about 8 feet 2 inches across, set 7 feet 3 inches apart along the table. Between them they cover a rectangle, which is the shape a table actually is.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Two 8 ft 2 in parasols instead of one
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Try it on the plan, then go outside and see.

It does not meaningfully change the beam in either season.

TestAn afternoonYou can undo it

A 9 ft 10 in umbrella

ForecastWorksstill Works

A 9 ft 10 in umbrella does not move this in any way worth the effort.

A 9 feet 10 inches canopy at about 7 feet 7 inches, tilted toward the low sun.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: A 9 ft 10 in umbrella
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 7 feet 7 inches and about four inches either way changes whether it works.

It takes the summer sun and leaves most of the winter sun, which is the behaviour worth paying for.

TestAn afternoonYou can undo it

Two low shielded lights instead of one high one

ForecastWorksstill Works

Two low shielded lights instead of one high one does not move this in any way worth the effort.

Add a pair of shielded 200 lumen fixtures at knee height near the seating, so the useful light is where people are rather than thrown across the garden.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Two low shielded lights instead of one high one
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 1 foot 8 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

TestA projectYou can undo it

A shade sail over the seating

ForecastWorksstill Works

A shade sail over the seating does not move this in any way worth the effort.

A sail about 16 feet 5 inches by 13 feet 1 inch, set at about 9 feet 2 inches and angled to shed water.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: A shade sail over the seating
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 9 feet 2 inches and about four inches either way changes whether it works.

It takes the summer sun and leaves most of the winter sun, which is the behaviour worth paying for.

TestA projectYou can undo itYears to work

A deciduous climber on tensioned wires

ForecastWorksstill Works

A deciduous climber on tensioned wires does not move this in any way worth the effort.

Wires strung about 8 feet 6 inches above the seating with a vigorous deciduous climber trained across them. In leaf it shades like a light pergola; bare, it gives back most of the winter sun a solid roof would have kept.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: A deciduous climber on tensioned wires
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 9 feet 6 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

TestA projectYou can undo it

Raise the bed 1 ft 4 in

ForecastWorksstill Works

Raise the bed 1 ft 4 in does not move this in any way worth the effort.

Build the bed up about 1 foot 4 inches with free-draining material. Roots sitting in water kill more plants than the wrong hardiness zone does, and lifting the root zone out of it is cheaper and far more reliable than trying to make the ground below drain.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Raise the bed 1 ft 4 in
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 1 foot 4 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA projectPermanent

An 8 ft 2 in awning

ForecastWorksstill Works

An 8 ft 2 in awning does not move this in any way worth the effort.

A folding-arm awning projecting 8 feet 2 inches from the house wall at about 8 feet 6 inches, retracted out of season.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: An 8 ft 2 in awning
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 8 feet 6 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA projectPermanent

Lift the crown of Dense deciduous tree

ForecastWorksstill Works

Lift the crown of Dense deciduous tree does not move this in any way worth the effort.

Raise the underside of Dense deciduous tree from about 7 feet 3 inches to 12 feet 2 inches. Light comes in sideways under the canopy, morning and evening, without losing the shade overhead at midday.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Lift the crown of Dense deciduous tree
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 12 feet 2 inches and about four inches either way changes whether it works.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

A pergola with open slats

ForecastWorksstill Works

A pergola with open slats does not move this in any way worth the effort.

A pergola about 13 feet 1 inch square at 8 feet 6 inches with open slats, slats running roughly south-west.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: A pergola with open slats
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 8 feet 6 inches and about four inches either way changes whether it works.

It takes the summer sun and leaves most of the winter sun, which is the behaviour worth paying for.

CommitmentA buildPermanent

An adjustable louvred roof

ForecastWorksstill Works

An adjustable louvred roof does not move this in any way worth the effort.

A louvred roof about 13 feet 1 inch square at 8 feet 6 inches, blades running south-west and closable.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: An adjustable louvred roof
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 8 feet 6 inches and about four inches either way changes whether it works.

It takes the summer sun and leaves most of the winter sun, which is the behaviour worth paying for.

CommitmentA buildPermanent

A paler paving

ForecastWorksstill Works

A paler paving does not move this in any way worth the effort.

Replace Mixed-exposure concrete slab with a paler paving of similar mass. The surface itself runs cooler underfoot; the trade is that more light bounces back up at a seated person.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: A paler paving
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

A solid canopy over the seating

ForecastWorksstill Works

A solid canopy over the seating does not move this in any way worth the effort.

A solid roof about 11 feet 2 inches above the seating, 13 feet 1 inch by 11 feet 6 inches, guttered on the low edge. Unlike fabric it works in rain, and unlike a pergola it takes the winter light too.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: A solid canopy over the seating
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Measure the actual height available before ordering: this is sized at 11 feet 2 inches and about four inches either way changes whether it works.

It takes the summer sun and leaves most of the winter sun, which is the behaviour worth paying for.

CommitmentA buildPermanent

Horizontal fins above the opening

ForecastWorksstill Works

Horizontal fins above the opening does not move this in any way worth the effort.

A run of fixed horizontal fins projecting about 2 feet 4 inches from House, set above head height. Geometry does the work: high summer sun is cut, low winter sun passes under, and the view out is barely touched.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Horizontal fins above the opening
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It takes the summer sun and leaves most of the winter sun, which is the behaviour worth paying for.

CommitmentA buildPermanent

Relay it as a permeable surface

ForecastWorksstill Works

Relay it as a permeable surface does not move this in any way worth the effort.

Relay Mixed-exposure concrete slab as permeable paving or resin-bound gravel over an open sub-base. Water goes down instead of sideways, so the spot dries hours earlier after rain and stops holding the film that makes it slippery and green.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Relay it as a permeable surface
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

A ventilated timber deck instead

ForecastWorksstill Works

A ventilated timber deck instead does not move this in any way worth the effort.

Replace Mixed-exposure concrete slab with a ventilated timber deck. Heavy paving charges all afternoon and radiates back until well after dark, which is why an evening terrace can feel hotter than the air. A light deck over an air gap is done within the hour.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: A ventilated timber deck instead
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It does not meaningfully change the beam in either season.

CommitmentA buildPermanent

Take up the paving and plant it

ForecastWorksstill Works

Take up the paving and plant it does not move this in any way worth the effort.

Lift Mixed-exposure concrete slab and plant it. Nothing else on this list moves surface temperature as far: paving in full sun sits twenty degrees or more above the air, while planted ground transpires and typically sits at or below it. It is also the only change here that gets better rather than worse over ten years.

Gained: Nothing here.
Lost: Nothing here.
Unchanged: Direct sun
Still unanswered: Nothing here.

The test: Take up the paving and plant it
If it worked: Barefoot crossing works for crossing barefoot at this hour.
If it didn’t: If direct sun still stops the hour after you try it, this was not the mechanism.
Next evidence: Try the reversible version first, even badly. A week with a borrowed umbrella tells you more than a drawing.

It does not meaningfully change the beam in either season.