Patio roof

[JohnBishop]

Hi Gents,

  I am planning to build a 4-leg patio this winter/spring. The patio will be covering my backdoors so the rainwater does not get into the kitchen. I reckon 3m x 4m
The roof is going to be simple slope. The patio will not be connected with the building barely touching it. I have external insulation and I don't want thermal bridging.
I think about some transparent material to put on the top as I don't want shade.
What material would you recommend?

 

Edited December 28, 2023 by JohnBishop

[JohnMo]

Make sure you allow for wind lift. Not quite the same, but we had a wooden structure with a roof, pinned down to lawn, one very windy night, it took off and parts of it went over a 6 foot wall. Luckily no one injured or cars damaged on the road where they landed.

[JohnBishop]

I am going to put some concrete bases for this and heavier timber I reckon 150x150mm

[gaz_moose]

twinwall polycarbonate sheeting. but i think its just going to be a massive sail. make sure you screw the roof down solid.

[JohnBishop]

I come across this man who done his pergola:

 

Very meticulous job however I think it's a bit overkill to my liking, feel too heavy over the head I think too much timer for this size of a pergola. I reckon rated for 100mph gusts. I think it creates too much shade though.
I would go for 6 posts tops but the concrete bases make sense. He used the twinwall polycarbonate sheeting.

Edited December 30, 2023 by JohnBishop

[JohnBishop]

Hi again, I am going back to this patio project.

3m by 2m between the posts.

The overhanging roof 4.2m x 2.60m at a sufficient slope.

 

I decided to go for 4x 6x6" posts.
All 4 will stand on 4x Simpson Post APB100/150 bases.

There will be two concrete bases forward, the back two Simpson bases will be screwed to the existing concrete base (by the wall).

I have no experience but I really like the mortis and tenon joinery. In this case I would use 5x5" timbers to marry it together.
I reckon it would be easier to use 2x12 girders instead however I want these not to obstruct the view from the window so the beam has to be 220cm above the ground (front). On the sides it does not matter but it will end up lower.

Then a roof structure on top made of 2x4" to accommodate polycarbonate sheets.

The wall is insulated on the outside so I cannot use it to support the patio like it is the case in most scenarios - it has to stand on its own millimetres away from that wall.

what do you think about his concrete bases. Is it sufficient or an overkill?

 

I have to put it all together in Sketchup.
Any advise welcome.

Thank you

[Onoff]

5 hours ago, JohnBishop said:

what do you think about his concrete bases. Is it sufficient

 

Insufficient imho. Our neighbour did similar for his fence posts. Cast concrete footings, let them set, then drilled and used expanding anchors for 4-hole metal post shows. Wind took the lot out. 

 

The kids tree house base here, 6+ 4x4 posts. I had galvanised brackets made up. 10mm side plates are bent at 90deg where they go into the concrete about a foot down.

 

 

 

Then with my 100x100x6 steel gate posts, I cross drilled and put 20mm dia stainless bar to anchor into the concrete.

[JohnBishop]

should I use different than Simpson bases? or something that is literally embedded into the cement while it is still fluid. Or even welded into the steel rebars that are sunken in cement?

[JohnBishop]

I understand the idea of vertical anchors is unreliable in this case because if the wind decides to lift the roof up it will take these anchors with ease but not if the anchors were horizontal or embedded in concrete.
Where can I get these brackets/anchors? How are they called?

[Onoff]

Loads about like this, all variations on a theme:

 

https://www.ebay.co.uk/itm/324527521877?gad_source=1&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338723872&toolid=20006&customid=e2YxEO0dAAAAI_-RymarhmEgWqwFAAAAAA

 

Think @ProDaveused similar on his?

[JohnBishop]

On 27/04/2024 at 16:10, Onoff said:

Loads about like this, all variations on a theme:

 

https://www.ebay.co.uk/itm/324527521877?gad_source=1&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338723872&toolid=20006&customid=e2YxEO0dAAAAI_-RymarhmEgWqwFAAAAAA

 

Think @ProDaveused similar on his?

so this 150mm variant would work for my 6" posts. I would do this for front posts.
 

What would be a better way of anchoring the back posts (near the wall) if I already have concrete there?

[Onoff]

4 hours ago, JohnBishop said:

so this 150mm variant would work for my 6" posts. I would do this for front posts.
 

What would be a better way of anchoring the back posts (near the wall) if I already have concrete there?

 

A case of horse bolted but hey ho. One option is to dig out the slab and recast proper pads. I imagine you're keen to avoid that.

 

Without seeing a photo and considering it's existing, then maybe a 4 hole base plate type but use stainless steel studs resin anchored into the concrete. Concrete needs to be a certain thickness ideally. 

 

Using resin anchors as opposed to expanding types anchors has a number of advantages.

- You can drill closer to the edge and have the bolts set closer together.

- Resin is better in cracked concrete.

- The anchor method itself doesn't put lateral (expanding) forces into the slab, with an expanding anchor too close an edge distance risks breakout. 

- The resin / stud combo fills the hole completely like a waterproof plug. Expanding anchors, even in stainless steel, can allow water to get in and freeze/thaw. Sometimes enough to crack the concrete.

 

The key with resin anchors is to have a clean hole to start with. Drilled to size and properly brushed and puffed out. 

[Onoff]

The Rawlplug load / depth table for their R-KEM II is a pretty good go to for resin anchors. Attached PDF. Note they say it's not for use in cracked concrete.

 

I happen to prefer Fischer products, specifically FIS V 360. They do give data for cracked concrete.

 

With any resin product I find it best to use the specific resin gun. You can mind get various resins in a single, silcone tube size for use with a normal mastic gun. I find that hard work. I did a little write up with pictures somewhere on here, will see if I can find it.

22828.RAWLPLUG.EN.R-KEM II POLYESTER STYRENE FREE RESIN CONCRETE.pdf LT_01_FIS-V-T2_F_SEN_AIP_V1.pdf

[Onoff]

Have a read on page 8:

 

 

[JohnBishop]

8 hours ago, Onoff said:

 

A case of horse bolted but hey ho. One option is to dig out the slab and recast proper pads. I imagine you're keen to avoid that.

 

Without seeing a photo and considering it's existing, then maybe a 4 hole base plate type but use stainless steel studs resin anchored into the concrete. Concrete needs to be a certain thickness ideally. 

 

Using resin anchors as opposed to expanding types anchors has a number of advantages.

- You can drill closer to the edge and have the bolts set closer together.

- Resin is better in cracked concrete.

- The anchor method itself doesn't put lateral (expanding) forces into the slab, with an expanding anchor too close an edge distance risks breakout. 

- The resin / stud combo fills the hole completely like a waterproof plug. Expanding anchors, even in stainless steel, can allow water to get in and freeze/thaw. Sometimes enough to crack the concrete.

 

The key with resin anchors is to have a clean hole to start with. Drilled to size and properly brushed and puffed out. 

In my case anchoring is quite important because polycarbonate roof is going to be a sail and it won't have that much weight like the guy's patio in the video. His is heavy on its own, has 7 posts and is wall mounted!

[Onoff]

5 hours ago, JohnBishop said:

In my case anchoring is quite important because polycarbonate roof is going to be a sail

 

You're not in Kansas anymore!

[JohnBishop]

This is the concrete. Not sure how thick it is. I reckon 3 inches?

 

Edited Monday at 22:25 by JohnBishop

[JohnBishop]

I dug into the concrete expansion gap and in two places I was not able to hit the soil but it looks like more concrete.
The gap is between 3-4 inches deep but how thick is the concrete below the gap I don't know? I cannot check around it as there is kerb all around it.

[Onoff]

Only you can decide on this at the end of the day but let just propose you use these at the back where the existing slab is. 

 

https://www.ebay.co.uk/itm/175719585849

 

It has x4 14mm fixing holes in the base. That dictates you'll use 12mm studs, (stainless of course). You reckon the slab is 3 to 4" deep. Look at the table, page 3 of the Rawlplug PDF as a rough guide for minimum substrate thickness, embedded depth etc.

 

This one takes 10mm fixing bolts:

 

https://www.amazon.co.uk/Heavy-Galvanised-Concealed-Support-Bracket/dp/B08FQV9XYW?

 

Tbh unless you pay a structural engineer to calculate all this it's best guess / a chance you take.