How many screws in boards and joists?

Ok, So i bought the 140x22mm boards. They Look great so far (sittin in the garage!)
I went and bought stainless steel square head deck screws, 53mm type 17, 9Guage. Got myself a nice makita impact driver too : )

I cant find any info on how many screws are required for the boards. I was told I need 3 screws, and I then I was told 2 screws will do, and then I was told to alternate between 3 and 2 screws....

My joists are 450mm, Do i screw teh boards down on every joist or every second joist?

I will be pre drilling every hole and countersinking them. The screws are self countersinking however I am afraid they will split my boards from another thread that is on this forum!

Any advice would be great. Im gonna start tomorrow morning! Will post pics.

I've always heard 2 are sufficient. I'm not sure on the placing from the outer edge, but someone maybe able to help out.
I have seen a deck recently built using 140 merbau and there were only 2 screws in these.
The most important thing is to use a jig for a consistent line of screws. As they're going to be a feature you don't want them wandering along the deck.
Some also say you need to put them off-centre to each other on the boards.
There was one drawn up on how to make one on this forum, so you could do a search for this.

Sorry I wasn't a huge help. You could use the search option, I find that most of my questions have already been answered here!
Hope it all goes well

Definitely screw every joist. I'd just put two in, 25mm from the edges.

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Originally Posted by clackerz

Some also say you need to put them off-centre to each other on the boards.

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That's to stop the joists splitting, but I doubt you'd have a problem with pine joists, so it's just a matter of what look you prefer.

OK so 2 it is. I have found thats its 20mm from the edge. I'll have to remake my jig.
I am not off centering them. Treatied pine joists should be fine. Sorry for asking the same questions..I want to get this right.

20/25mm, wouldn't really make much difference. Perhaps there's a technical manual out there somewhere if you want to get fussy, but I was just envisioning it in my head. :wink:

cool, stainless steel screws look realy good in a deck. Here is a good tip. A lot of people dont get there deck sanded after the install, but i can tell you that the difference between getting it sanded and not is worth the process of getting it done. It is simple and can be done with a orby. It just cleans up every thing just nicely before you coat it. In north Queensland, i used to sand heaps of them for builders. But trhey were big decks and we used our floorsanding machines. the deck was crisp and clean before we coated it. Also We always used oils, Feast Watson or cabots is good,. Gotta go, my 75 year old motherin law wants a cuppa tea.

O buy the way 2 screws countersunk 3mm 20-25 in from the edge in a staggered line is good.

140mm wide boards 22mm finish we'd generally go stainless bugels 75mm 2 per joist as the bigger boards have more power to move around plus the customer who wants wider is usalll after the jetty look so the bigger fixings go with the bigger board and bigger budget LoL...
Either way bring the screws in approx 30mm from the edge to spread the holding power .... 9 gauge ???? thought it was 8 or 10G

cheers utemad

Im with Utemad Gav,

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Originally Posted by Larry McCully

Im with Utemad Gav,

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Geeeeez thanks Larry ...... I might get round to putting the stair photo's up ....What do ya reckon ....could give you a plug aswell but have to wait and see....LoL

Should see the deck on the front and the pergola now .... 6x6 merbau posts and chunky as you know what... I will get a happy snap when i go back and post it for all the hardwood fans amongst us along with a before to see the change.... Boy did that one cost in timber and milling

Cheers utemad

Yeah I thought 8 or 10g but I will take a foto of the box and show you taht its actually 9g and they are 53mm long...strange sizes...

I've gone 20mm in, I only laid 5 boards today..too much stuffing around trying to work everything out....
Got a good production system going now so I'll be able to lay heaps. I been countersinking them..

I have noticed that I have to stand on the board when Im screwin them down as the boards lift up a little when they are getting screwd down. Im so glad I bougt the impact driver...screws go in like they are in butter.

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Originally Posted by oohsam

Yeah I thought 8 or 10g but I will take a foto of the box and show you taht its actually 9g and they are 53mm long...strange sizes...

I've gone 20mm in, I only laid 5 boards today..too much stuffing around trying to work everything out....
Got a good production system going now so I'll be able to lay heaps. I been countersinking them..

I have noticed that I have to stand on the board when Im screwin them down as the boards lift up a little when they are getting screwd down. Im so glad I bougt the impact driver...screws go in like they are in butter.

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The impact driver is definately the go.... we use 3 when doing large decks so as to rotate them and save burning them out as we screw off the whole deck in one go generally....
The board shouldn't stand up if your pilot hole in the board is 1/8 inch for a 10g screw and the tip is a type 17 point to cut into the joist....

cheers utemad

Hmm...
Im using a 3mm bit for the pilot hole for the 9g Screws and they are type 17...
I was looking at the deck this morning, one of the boards a little thicker than the others and you can notice it when walking on the deck..Should I pack out the other boards just a little to compensate?

I would measure the difference in thickness and plane down the thicker one to match. But first make sure it is just the board that is thicker and not your framing .

I see. I have a good electric plane that I will put to use.
When planing merbau, will you be able to notice its been planed..ie, in the colour?
You can tell with most wood once its been planed.

Not unless you climb under your deck to look at it. :wink:

heheh oh...from underneath! Silly me..Here I am thinking i'd plane the top of it off once I've screwd it on...Derr....sorry.

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Originally Posted by pawnhead

Not unless you climb under your deck to look at it. :wink:

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Aw har hae har har har harrrr, Arrr that was good

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Originally Posted by UteMad

The impact driver is definately the go.... we use 3 when doing large decks so as to rotate them and save burning them out as we screw off the whole deck in one go generally....
The board shouldn't stand up if your pilot hole in the board is 1/8 inch for a 10g screw and the tip is a type 17 point to cut into the joist....

cheers utemad

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Hey Utemad,
I'm gonna be using the square drive Type 17 point to go into F17 120 x 45 joists. I assume they need pre-drilling all the way down? Or can I get away with only drilling and counter sinking the merbau board.
Also, what do I need to do when coming to joins. I'm reading all this 20mm from the edge stuff. Your thoughts on 140 x 22 merbau decking joins on 120 x 45 F17 joists would be greatly appreciated. Oh, and I'll be driving them in with my Pana 14.4v Li-Ion Impact Driver.

Awaiting your reply,
Cheers,
Akilas.:?

You dont predrill all the way into the joist. The screw will go into the joist without any trouble, but you just want to predrill and countersink the merbau. You want the screw to grab the joist and thread its own patterin int the joist, hence the need to not predrill in joist.

The 20mm in from the edge really has nothing to do with the joist, its all about the merbau. The further in from the edge you are the less likely your board will crack at the edge. 20mm is a safe distance, just make sure you hit the joist!

I used a makita 14.4v impact driver. I gave it a rest every 45mins or so coz I didnt want to kill it. Had a battery on charge and a battery on the go at all times. You'll find you get better results if you blip the impact driver as the screw goes down.

I found some boards lifting a little, it may have been becuase my pilot hole was too small, but I was using 3mm. I just sat or kneeled ont he boards when screwing them in, and letting the impact driver spin the screw 1 or 2 more times once the screw is flush with the board to pull it down a little if need be.

Some of my countersinking was too deep, so keep an eye on that. I used a sperate drill for a countersink, I should have tapped it so i knew where to stop but i was lazy.

Good luck. Cheers.