Landscape & Garden Design
Jul 15, 2009 8:26 pm
Hello all, I have some questions which I'd like you guys to help me out with.
I have just built a colourbond c section gable patio structure attached to the back of my house. Its dimensions are 11.3m long x 5.6m wide. 4 poles on the 11m side and attached to the house on the other. Passed and approved by council.
Because it is fully undercover and will rarely be getting wet I want to build my deck with virtually no spaces between the boards.
I will be using 100x100 bearers, with 100x50 joists. I will have 5 bearers evenly spaced to cover the 5.6m. Bearer 1 nearest to house, possibly freestanding on stirrups or as a ledger attached to the house. Bearer 5 will be furthest from the house. Bearer 4 and 5 may have joists within bearers using joist hangers to keep some height above ground level to aid in ventilation.
I will be ( with the use of a car jack) pushing the 90x22 treated boards up against each other nice and tight to eliminate any gaps. I have done this in the past and have found there to be no adverse effects of having less ventilation between boards due to no gaps. I have found this to look and feel better, in my opinion, compared to a deck with 3mm gapsthat grow as it dries out further.
Has anyone else done this, and are there any issues I should consider, the deck will be quite large and reasonably low to the ground. I dont know if ventilation is such a big problem as because it will be undercover it should only be getting wet on occassion when I might be hosing it off.
Re: Near ground level deck question, no spaces between boards.2
Jul 15, 2009 8:32 pm
You will have a few issues.
You might not get direct precipitation, but you will get side rain and moisture if there is nowhere for the water to go, or for it to dry out. Dont spill anything or wash it down?
Also movement will be an issue, as you will find in time your deck will move as the earth and the house does (and they will). I would leave an expansion join somewhere so the boads can move a little. Perhaps off the house by 2-3mm might e enought.
Davinci would be able to give a good idea.
Re: Near ground level deck question, no spaces between boards.3
Jul 16, 2009 7:55 pm
min. 150mm below bearers to soil. if deck area is a low point then aggy drains maybe needed. min. 4mm gap to allow for expansion etc as per Adrian b. use screws ie: bugle not nails (screw shank, ring shank on wide boards 90mm + width) if plating to house make sure you dont cover vent holes in brick work, use galv nails in subfloor etc
Da Vinci Outdoor Living Architectural landscaping http://www.davincioutdoor.com
Re: Near ground level deck question, no spaces between boards.4
Jul 16, 2009 8:34 pm
Thanks for the replys guys.
There are no vents on house walls that will be covered up.
Deck will not be attached with ledger to house but free standing.
There is an ag drain that runs the length (11m) of the patio cover approximately 1500mm from the house. Ground slopes in the direction to the ag drain. Ground level has been levelled to slope slightly and additional bluemetal added to ag drain to aid drainage.
Yes in the event of wind and rain at an angle some of the deck could get wet.
I was hoping that there would be enough airflow beneath the bearers, ranging from 50mm to 125mm to allow for no spaces between boards.
I have a section 6.6m long and 3.8m wide on the NE side of my house, 600mm off the natural ground level, that has the decking boards pushed together tight in the same fashion. I prefer my deck finished this way, as it feels and looks better in my opinion. It is mostly under the House roof, with the exception of 1m at 6.6 long and gets wet whenever it rains. Its been erected for 18 months now and shows no sign of damage due to getting wet, but admittedly it dries out well probably due to the extra height clearance.
I will try and add some pics tonight after work.
Re: Near ground level deck question, no spaces between boards.5
Jul 17, 2009 1:21 pm
You can make up a jig to make your nail/screw holes all the same line as your joists. Just use a piece of offcut decking timber with 2 nails in the bottom to sit either side of the 45mm joist, and pre-drill a hole that lines up with the decking boards to where you want to drill your pilot hole. Then you can nail or screw to the deck with always the same spacing and measuremet off the edge of the board. It's very easy to use one of the nails as a spacer between the decking boards, just use a few lightly tapped in along the length of the boards while you install them, then take out to move to the next board. Just remember to test your parellel every few boards to make sure it is still square.
You will need the gaps between the boards, as during the hot/cold/humid weather extremes the timber expands and contracts; if they were butted together they would buckle if this happened.
Re: Near ground level deck question, no spaces between boards.6
Jul 17, 2009 7:20 pm
Have seen treated pine decking pop up off the nail when it was laid in tight with no gaps. I've also seen hardwood decking snap screws when its been butted in tightly.
A 3mm-4mm gap is perfect.
Why the heck would you need a car jack to push softwood decking boards together??
The only time you would lay decking boards butted up together is if you are using unseasoned decking boards, which are seldom used these days
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