Thread: Deck Spacing

Hi All

Having some merbau decking 140 mm put down as a board walk.
The area will be exposed to the elements.( 4m x 4m L shaped)
I would like to have them tight for its appearance ( seen at some new display homes) but not sure what problems will arise in the future.

If gap is required, any experiences what is minimum for looks and fit for this size board.

Also, any suggestions for for weed control if gap required


Also using the same board in a covered gazebo 6m x 4m
As it wont be having rain on it, is having it without gap ok?

Im sure others will say this, but if you do put them down with no gap, they will shrink an soon enough a gap will appear. I am putting down some 140mm decking this weekend if I can get the timber today, and personaly i think it looks more stunning than the 90mm, but, i'll be using a nail to gap them..That way atleast I know the gap will be the same between all the boards...

Don't forget that boards don't only shrink when they dry, they also expand when they're wet. The wider the board, the more it will move.

I think that trying to set the gap with something referencing each board as you go along is almost guaranteed to result in wobbles. The best way to do it, (yeah yeah, broken record) is to lay every fourth or fifth board to a chalk line and then fill in between them, using wedges to set the gap. That way you are guaranteed to end up with straight lines. With your method, if one board is a bit fat at one end, or it springs back after you nail it, you can end up with an error that compounds itself as you lay successive boards. If I can convince one person on here to give it a try then I will consider my job done.

Silent C - So are you saying that I should screw down every 4th board (according to measurements) and then fill in the gaps with the remaining boards.

Forgive my stupitidty, but I cant see how this will keep the gaps the same could you possibly explain, what spacing do you reccomend for 140mm boards?

also, do u reccomend 3 screws in each board or just 2?

So are you saying that I should screw down every 4th board (according to measurements) and then fill in the gaps with the remaining boards.

Yes. Well, I do every 5th. It's not so much about keeping the gaps the same, although that is part of the objective, it's about keeping the lines straight, so that when you look along the deck, you see a nice set of parallel lines and no wobbles. It also ensures that when you get to the other side of the deck, your last board is not a trapezoid.

I've never had anything to do with 140mm decking. I use 90mm and I go for between 3mm and 5mm gap, depending how it works over the width of the deck. The bush fire building requirements here specify 5mm. Mine have opened up a mm or two since I laid them.

See this thread for my advice.

heheh thanks pawnhead...I knew of that thread, since I started it...but Im tryin to double check everythign before I do it, coz I have a feeling I will fudge something!!!

One day I'll convince him to try it my way

When you've laid a few decks on contract, then you try to save a bit of time and you get good at using your eye, but for a novice it may be wiser to set everything out using chalk lines as suggested by silent.

But if you can't see a bow in the boards by putting you're head down at the end, then it would be less than a couple of millimetres, and no one will see it by staring down at the finished product from above.

Actually I have to admit I did the first run of our verandah, and it was the longest - about 12 metres, before I found out about the method I now use. Considering how I did it, it's not too bad. I still put in only every fifth board, but I used a couple of spacers about 400 mm long to position the board on the joist relative to the first board. Then filled in the blanks using a couple of bits of fibro and a chisel to set the gap. It works OK, you just have to be careful.

The advantage of the method I now use is that it works really well if there's more than one of you. What I have done in the past with a helper is get them to help with cutting and nailing down every fifth board. That's the fiddly time-consuming bit. Then one cuts while the other calls out measurements and places the fill-in boards. Once all the boards are cut and in position, you grab a bucket of wedges and one goes along each joist with the wedges adjusting the gap to eye while the other nails. You let the wedge guy get a bit ahead. Then as you move along, he goes around and picks up the wedges behind you and continues on. Once you get a routine going, it is very fast.

But anyway, for a one off, the most important thing is that you keep this problem in mind - don't assume that every board is the same thickness and don't assume that if you just use a spacer and start at one end you will finish where you thought you would.

Hmm I see.
It will be only me on my own laying the boards, so it will take me longer..

How about this for an Idea:
Set a string line for where every 5th board should be and then I'll know once I get there how far out I am and then I can adjust each board a little till I get to the next string line.
I dont wanna stuff it up so once I get to the 5th board, the 4th board wont fit!

If you get to the fifth board and you're out of whack with your string line, you'll be chasing your tail to try and get it back on track. The way I do it, you can't possibly go wrong - as long as you make sure every fifth board is straight. Even if your deck is not perfectly rectangular, you can creep one end a bit so that you have even spacing.

If you want to use a string line rather than a chalk line, offset the line from where you want the board to be by 19mm and use an offcut of decking to check the gap between the board and the line at each joist and adjust accordingly, rather than trying to set the line to where the edge of the board will be. If you do the latter, it's hard to line the board up with it without moving the string line.

BTW my method doesn't necessarily take any longer for one person, but it really comes into its own if there are two of you.

Ok.
I will use your method Silent C...I have understood everything and if It fails me I will come looking for you!!
Just kidding. It sounds fairly easy.

Ahh, but it's not my method, it's Gerry the carpenter's method - I'm just his disciple, so you'll have to go looking for him

Whichever way you do it, if you take your time and think about it, you'll be fine.

My 2 cents worth.
I personally chalked every board because I was so paranoid about the look. This worked fine on the sections of my deck that were square to my house. Unfortunatley my pool was not square to my house and I ended up having to vary my gaps to 'fudge' 60mm. This allowed me lay the last board as a full board and avoid any trapezoid shapes that would've enhanced the problem.
I'm only a novice but, in my experience, definatlely chalk your lines and don't just rely on keeping your gaps uniform. You'll find the boards will vary greatly in size.

Thanks for the replies.

Decided for the 3mm gap for the board walk and deck as well for consistency.

will post some pics as it progresses.

I've just put down 5 boards and used a 3.75mm nail as a spacer. I think the gap is a little big so Im goin down to 3mm to see how it is.
Will let you know. Im also using the 140mm boards. They look amazing.