I’ve decked teh rear of the garden on 150mm decking joists as it’s elevated.

I need to deck another portion of the garden, essentially on top of the old patio.
realistically, I can only ‘fit’ 70mm tall decking joists there as I need to bring the fisished decking level with the bifold doors, and, well, only 70mm decking will fit.

I guess this will be OK, right, as it’s essentially NOT elevated, but jsut resting on the patio/packers below….?

I’ll have noggins to prevent twisting etc….

DrP

Aye, that’ll be plenty.

It’s not the Empire State Building you’re constructing .

I’d imagine the risk of death to be relatively low.

As a highly trained construction professional of 25 years standing I give you my express permission to crack on.

Plenty of scurrying  room for teh rats underneath that.. all good to go

Mines on 70 my joists and me and the missus have jumped up and down on it and haven’t fallen through.

I’d imagine the risk of death to be relatively low.

What are we talking…like, 7-12%?? I can live with that I guess….!!

I’m a perfectionist and over-engineerer…I simply don’t want it to be flexing and creaking!!.. seems like well packed out 70mm joists will be dandy!

Will update with pictures once didded….

DrP

What are we talking…like, 7-12%?? I can live with that I guess….!!

You disappoint me.

Han Solo would never want to know the odds.

Be like Han

I’m a perfectionist and over-engineerer…I simply don’t want it to be flexing and creaking!!.. seems like well packed out 70mm joists will be dandy!

Just pour concrete between the 70mm joist to hold them in place. Couple of sheets of rebar as well for good measure. Have you thought about adding some 5m piles, just to make sure it’s OK?

I’m getting the structural engineer to assess for possible ground movement, before I drive in the piles (only 4m though…eek…)

😉

DrP

Make sure you take some groundwater samples to make sure you aren’t disturbing any previous contamination that might have been re-mediated.

Can’t be too safe 😉

You’ll need to hire Party Wall Surveyors for both neighbours as well, just in case you collapse the street into a sinkhole…

 before I drive in the piles (only 4m though…eek…)

This is one of the scariest sentences that a Doctor can say to you.

Whatever you do, don’t start work on-site before you’ve completed a full Paranormal Survey.  Building decking of any joist dimensions atop ancient burial grounds is a big no-no.

^^ LOLZ…

Anyway, this might all never happen if full planning permission (including ‘change of use from patio to decking’) and the arial survey aren’t granted….

DrP

I simply don’t want it to be flexing and creaking!

I find 70mm joists really make the patio come alive.

Wildlife survey complete?

Archeology survey complete?

Whatever you do, don’t start work on-site before you’ve completed a full Paranormal Survey.

Yep, I once saw a documentary about some housing estate built on an old burial ground. Didn’t end well for their daughter…

Archeology survey complete?

Under a patio? Nothing to see under there surely.

 I need to bring the fisished decking level with the bifold doors

Serious question, will this still give a difference in height between the deck and damp proof course?

I assume he’s extending the damp proof course over the whole decking as per STW regs 1026:109.6

Under a patio? Nothing to see under there surely.

He’s a doctor, got a whole system to dispose of his problems without getting his hands dirty, Harold Shipman never laid a patio in his life.

RE DPC… so the DPC is still a few inches above the decking…

Plus more was laid around the threshold of the doors, with a sort of return on it..

My decision is whether to have the finished level of the decking ‘as level with the threshold’ (top image) or level with the sil (bottom).

Of course, there’s be a gap around the decking plank on the top diagram, to let water run off/under…

Hmm..

DrP

I think you need the outside either level with the inside or there to be a noticeable difference. My experience of watching thousands of medical professionals negotiating exhibit stands suggests that small differences confuse the brain and cause people in a hurry to pick up a free pen to somehow miss their footing and throw themselves to the ground.

firstly, if I’m reading right, the 70mm will be sitting on the patio. If so, you’re good to go. Not sure where you think the joists are going to move too with decking screwed through at the same intervals that noggins would space at, but if it makes you feel better you go for it!

Height next to DPC, won’t be an issue. The water won’t sit at decking level, it’ll drain down to patio level. It’s standing water / damp ground you’re protecting against so it’ll be fine.

Be careful that there is a gap from the decking to the bifold door sill however as if it’s touching, or within a few mm you’ll have water sitting there and the sill / decking will rot. Again, not an issue with aluminium frames and composite decking of course!

As a highly trained construction professional of 25 years standing I give you my express permission to crack on.

He’s saying this because he kniws you can cut costs. Which as a QS means he can justify his massive cut if the total budget.

I’ve decked teh rear of the garden on 150mm decking joists as it’s elevated

I hope it’s either not elevated more than 30cm, or you had planning permission for it?

Plenty of scurrying  room for teh hedgehogs underneath that.. all good to go

That’s if you’ve got hedgehogs around; ideal hibernating spot, put nice dry bedding hay underneath, they’ll love it.

Under a patio? Nothing to see under there surely.

That’s the hope, usually…

Greybeard…. nah it’s only 60mm AT MOST (plus the 150mm joist).. The rear corner of the garden is simply a tad uneven..

DrP

it’s “northshore”, not decking

err, dood

Dear god it’s got to be the 150mm ones although you may need to whittle them by 80mm or so.