# Forum Home Renovation Decking  How to join decking boards

## Poirot

There are often questions about here about joining decking boards; should you have double joists, or just butt join on a joist and have 4 nails or screws on the same joist.
Whenever I build a deck, I mitre the joints. That way your nails or screws line up unlike with double joists or other butt joints.
I'll add a few pics to illustrate:  
Mitre cut your first board, making sure that is sits just half-way or less than half way onto the joist.   
Best idea is to put a small galvanised nail in the first board, that will prevent the board from moving sideways later.   
Mitre cut your next board and put together.  
Now put your screws in the middle of the joist. 
Because your other board was not sitting on more than half of the joist, your screws will be about 20 mm at least from the edge of the top board, and will be lining up with the boards next to your mitred boards.
Once the joint is sanded flush and oiled, only a person who ever built a deck will spot the joint  :Smilie:  .

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## Bloss

Good photos and description with good result, but a butt joint with a slight undercut is all that is needed and for most DIYers will be faster and easier to achieve IMO. Most important at all ends is to properly pre-drill to prevent splitting.

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## Poirot

> Good photos and description with good result, but a butt joint with a slight undercut is all that is needed and for most DIYers will be faster and easier to achieve IMO. Most important at all ends is to properly pre-drill to prevent splitting.

  Absolutely no problem with that, except then your screws/nails do not line up with the rest of the boards on that joist. That is the main benefit of what I was trying to show; just try to spot the join in the first pic below.

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## jimj

It is always nice to see another technique- method in deck construction. Great photos & explanation. I am sure it will be adopted by someone who reads this thread. 
jimj   restore-a-deck.com.au

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## Bloss

:What he said:  yes good to have straight and aligned screws, but frankly like most things virtually no-one ever notices these minor details and few are prepared to pay extra for the time to do them. Most want a deck to use as deck and although a DIYer or even a new homeowner might be pleased to have such a finish that's transient. Like most work - what stands out just after it's been done as a great piece of work, or as a flaw, are forgotten so quickly as the structure becomes used for it total purpose. Doesn't mean we can't take pride in good work though - and that is good work!  :2thumbsup:   
I also like your corner treatment and have used that and mitres too - but that is simply an aesthetic choice. I have suggested various options for changes of direction at junctions or herring bone or chevron or other decking layouts to clients and often find my preference varies from theirs - they get to choose of course.

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## DylanB

That looks fantastic where you changed direction any more pics of that?

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## Poirot

> yes good to have straight and aligned screws, but frankly like most things virtually no-one ever notices these minor details and few are prepared to pay extra for the time to do them.

  Well, this is my problem:  This is my own houseI have to live here and look at it all the timeBut the biggest problem trying to build something is that I am a cabinet-maker by trade, so I end up applying cabinet-making perfection to carpentry which I have to learn to let go off; it's a bit of a curse really ...

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## Poirot

> That looks fantastic where you changed direction any more pics of that?

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## billyt

IMHO, the best method of corner treatment for a deck. Hers's one I'm doing at the moment. Boards are spotted gum 140mm x 25mm finished size.<br>
Sorry for the thread hijack<img class="inlineimg" title="Wink" border="0" alt="" src="http://www.renovateforum.com/images/smilies/standard/wink.gif" smilieid="655"><br>&nbsp;<br>

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## r3nov8or

Something I always avoid in exposed situations is 45deg mitres due to the limited durability of a feathered edge. I'll be interested how the OP's delicate exposed edges hold up over the years.

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## Bloss

> Something I always avoid in exposed situations is 45deg mitres due to the limited durability of a feathered edge. I'll be interested how the OP's delicate exposed edges hold up over the years.

  So long as well maintained should be fine - the cabinet maker precision and attention to detail shows through.  :2thumbsup:  A bit OC, but its his house!  :Cool:

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## Bloss

> IMHO, the best method of corner treatment for a deck. Hers's one I'm doing at the moment. Boards are spotted gum 140mm x 25mm finished size.
> Sorry for the thread hijack

  mmm - what are those shiny bumps - jimij will be apoplectic . . .  :Smilie:  :Wink:  not many fans of dome heads on here . . .  :Redface:

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## Poirot

> not many fans of dome heads on here

  There are for the blind, so they know they get to the edge of the deck; you know like at the pedestrian crossings etc ...  :Biggrin:

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## r3nov8or

> So long as well maintained should be fine - the cabinet maker precision and attention to detail shows through.  A bit OC, but its his house!

  Weatherboards are no longer installed with mitres for the reason I've suggested (unless possibly for heritage reasons).  
Anyway, kudos to Poirot for taking the time.

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## billyt

> mmm - what are those shiny bumps - jimij will be apoplectic . . .  not many fans of dome heads on here . . .

  Not my call........it's what was specified.

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## jimj

Gotta love those specifying folks behind the scenes. Sometime down the line or even when this deck is built it can't be sanded to coat. As I sand brand new timber to coat I would be in a quandry.  So will the owners of this house sooner or later. Yes it is under a roofline but the coating on the  outside boards will still eventually give up and need fixing. As long as they are happy to have the nails punched then no problems. However, when I arrive at these scenarios the hapless owner will either ask me why they used them in the first place? Or they have already contacted the designer,builder & first time painter all to be fobbed off with thats what was specified and we don't want to know about it. 
A case of buyer beware & builders today putting forward the pros& cons of nails versus countersunk screws or educating the %%^&*% specifyers.
 Its been awhile since a good ole sunday rant. Starting to feel better already!  :Biggrin: 
jimj   restore-a-deck.com.au

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## ringtail

> mmm - what are those shiny bumps - jimij will be apoplectic . . .  not many fans of dome heads on here . . .

  
I still like them  :Biggrin: . I'd be more concerned with the no primer anywhere and lack of joist protection

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## jimj

Thanks Bloss ! I always wondered what I was suffering from. Nice to know I am apoplectic. Now, if I only knew what the word meant! 
jimj

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## METRIX

> IMHO, the best method of corner treatment for a deck. Hers's one I'm doing at the moment. Boards are spotted gum 140mm x 25mm finished size.<br>
> Sorry for the thread hijack<img class="inlineimg" title="Wink" border="0" alt="" src="http://www.renovateforum.com/images/smilies/standard/wink.gif" smilieid="655"><br>&nbsp;<br>

  Nice work, As much as the dome heads are not liked, you have done a fantastic job of lining everything up, from the boards tot he gaps to the nails in both directions, well done, hope the owner appreciates the amount of extra work it takes to do this.

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## gpkennedy

Hi Poirot, those are very good ideas and pics of a well finished deck. I look at my well seasoned 15 yo deck and wonder why I didn't think of your ideas earlier. How do you efficiently countersink the screws into the deck? Damn good job.

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## intertd6

By joining boards with a mitre like shown would seem to me like a place for a squeaking board to appear & there is not much timber actually holding the end of the board structurally, if a point load were to be placed on the board between that end & the next joist it could be weaker than the usual butt joining method where the fasteners have more timber around them.
regards inter

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## stevoh741

x2 on where is the joist protection (spotted gum deck). Also my concern with the dome heads is that when those 140 boards want to cup (and they will - I use them all the time), dome heads aint goig to give much holding power. I only batten screw them and even then some cupping (minimal though) still occurs. 
Great job on the setout though  :Biggrin:

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## ringtail

> Well, this is my problem:  This is my own houseI have to live here and look at it all the timeBut the biggest problem trying to build something is that I am a cabinet-maker by trade, so I end up applying cabinet-making perfection to carpentry which I have to learn to let go off; it's a bit of a curse really ...

  
I hear ya. When I changed trades from a motor mechanic to chippy, going from measuring in thousands of an inch to + or - x mm was hard to deal with. Drove my boss mad  :Biggrin:

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## ringtail

> By joining boards with a mitre like shown would seem to me like a place for a squeaking board to appear & there is not much timber actually holding the end of the board structurally, if a point load were to be placed on the board between that end & the next joist it could be weaker than the usual butt joining method where the fasteners have more timber around them.
> regards inter

  I still like the undercut butt join myself. I'd like to see a bit more board over the joist too. I'd be very anal with getting the join smack in the middle of the joist so each board has adequate bearing. I do really like the set out though. Top work billyt and poirot

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## Poirot

> By joining boards with a mitre like shown would seem to me like a place for a squeaking board to appear & there is not much timber actually holding the end of the board structurally, if a point load were to be placed on the board between that end & the next joist it could be weaker than the usual butt joining method where the fasteners have more timber around them.
> regards inter

  Both boards have 19mm bearing on a 38 mm joist, just like a butt joint. 
In a butt join installation, the distance from the screws to the end of the board is about 15 max, in the case as illustrated here, the screw is about 20 to 25 in from the end of the top board.
No squaks if you use screws; and in a deck that is about 10 year old which I did back then, the joints were fixed with galvanised deck nails, and the joins are still all flat (hardwood joists, not pine).

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## Poirot

> Hi Poirot, those are very good ideas and pics of a well finished deck. I look at my well seasoned 15 yo deck and wonder why I didn't think of your ideas earlier. How do you efficiently countersink the screws into the deck? Damn good job.

  I used the Macsim Clever Tool. Butr because that is made for softwood, the drill (3.2mm) is not big enough for hardwood, so I predrilled with a 4mm bit, then countersunk with the Macsim Clever Tool (with a shortened drill bit just long enough (6mm) to line up with the 4mm hole and so it does not keep breaking).

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## ringtail

> Both boards have 19mm bearing on a 38 mm joist, just like a butt joint. 
> .

  
Not really. The darker board is sitting 19 mm on the joist as you say but, the *full thickness* section of that board is only just on the very edge of the joist. Its unlikely to give you dramas but in the right situation with the right point load it could fail. (Think 120 kg women in stillettos  :Biggrin: )  50 mm joists would give ya heaps more to play with.

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## Bloss

> I hear ya. When I changed trades from a motor mechanic to chippy, going from measuring in thousands of an inch to + or - x mm was hard to deal with. Drove my boss mad

  Chippies use precise fine measures eg: 'move it a 'poofteenth' to the left will ya", " yeah, its a 'beesdick' from fitting right" or "just tap it a 'smidgin' over will ya" - those measures ensure it all fits together tightly . . .  :Wink:  :Biggrin:

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## jimj

> Chippies use precise fine measures eg: 'move it a 'poofteenth' to the left will ya", " yeah, its a 'beesdick' from fitting right" or "just tap it a 'smidgin' over will ya" - those measures ensure it all fits together tightly . . .

   Thanks Bloss,no doubt these technical terms ( phrases) in building must be linked to the word apoplectic. Although, I would be totally censored if I used my apoplectic phrases. :Biggrin:  
jimj

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## jimj

Technical phrases used, expressed, uttered, yellled ,screamed, mumbled,thought of,should have thought of at the time but didn't, could result in a new thread! 
jimj

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## ringtail

Just finished making a box with all the fancy dovetails etc.( poirot the cabinet maker rolls eyes  :Rolleyes:  :Tongue: )...and there was much beesdicking and poofteenths  :Biggrin:  :Biggrin:

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## stevoh741

> (Think 120 kg women in stillettos )

  I am trying my hardest not to.....no doubt they are sporting lycra tights too :No:

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## intertd6

> Both boards have 19mm bearing on a 38 mm joist, just like a butt joint. 
> In a butt join installation, the distance from the screws to the end of the board is about 15 max, in the case as illustrated here, the screw is about 20 to 25 in from the end of the top board.
> No squaks if you use screws; and in a deck that is about 10 year old which I did back then, the joints were fixed with galvanised deck nails, and the joins are still all flat (hardwood joists, not pine).

  This method is actually defective in a couple of ways because there is not the required amount of fasteners in the lower board, the fasteners in the top board miss the bottom board completely, furthermore even if the required amount of fasteners were in the bottom board they are not holding structurally in the full thickness of the timber either, with the  end bearing in this method the full thickness of the bottom board is not supported with the minimum end bearing distance.
regards inter

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## ringtail

> I am trying my hardest not to.....no doubt they are sporting lycra tights too

  Thanks for that Steve, I have stuck a fork in my eyes due to the Lycra image  :Biggrin:

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## seemax

My son's school has a deck using this mitre joint method and merbau 140x19mm decking. 
After 3 years at least 50% of the joints have splayed up or cupped, not only does it look average but it creates a splinter risk.  
Might be less risk with thicker (eg 32mm) boards.

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## Dean38

> My son's school has a deck using this mitre joint method and merbau 140x19mm decking. 
> After 3 years at least 50% of the joints have splayed up or cupped, not only does it look average but it creates a splinter risk.  
> Might be less risk with thicker (eg 32mm) boards.

  
Would a flexible or rigid glue help the mitre join or does it need to allow movement there?

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## Bloss

> Would a flexible or rigid glue help the mitre join or does it need to allow movement there?

  No . . .

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