Decking Experts...i have some questions :)

Fidgetsmum did it 'cos she didn't know any better!

 

Hi Fidgetsmum.
Well done you for taking on the job ,plenty wouldn't..
Many ways to undertake a decking job, and even though not done by the book don't worry ..
Maybe if Cooperidol was to dig out the soil and weeds under each slab (using the slab instead of the concrete block ) then lay slab on concrete base so it was just above ground level,this would then keep joist off the soil and still give enough clearance for the door frame.. (what size joists were you thinking of ? )
Dave

 

Hi dave... What do you mean by laying the slab on concrete? I'm gonna use 4x2 joists... I Only have 5 inches From grass to door cill at the moment, so had planned to take the top 2 inches of grass and soil off there by giving me enough room to lay the deck..... 1 1/4 paving slab + 4" joist + 1 1/4 deck board = 6 1/2
I suppose I just want someone to tell me that it definitely won't sink if I lay it on paving slabs alone... But I suppose there are no definates!

 

It would be easier to get your slabs level if they were laid on a bed of concrete of mortar..It would have been better with a bed of concrete but as you are tight for depth use a mortar bed instead (building sand and cement ) Maybe you could digout just a little deeper to allow for the mortar. I'm sure you can do it just plan it out before you start .

Dave

 

I've built quite a few decks before both ground lying and elevated and having tried the paving slabs and suffered leveling problems and sinking now always concrete posts into the ground. Bags of post mix mean you don't need to mix anything. Simply dig a hole about 1.5 to 2 feet deep, fill the bottom 4-6 inches with hard core, bricks, rubble etc and compact down then insert your over length 4x4, level up and fix in place with temporary stakes. Fill the hole with the post mix and add water. Wait about 12 hours then add water to some ready mixed cement to make a fairly stiff wet mix and trowel on top of the concrete to form a water run off angle. This will save the post somewhat and its all pressure treated so in theory should be good for 20 years unless you get wood worm. By then the whole lot should be ripe for replacement anyway as it doesn't last forever. If you have very wet ground, consider getting elm posts from a hard wood timber yard. Elm lasts pretty much indefinately when submersed in water. The wetter the better. It's then very easy to level up the joists. Simply level with a spirit level and screw to the posts. Once in place, saw the long ground posts flush with the top of the joists. I use joist hangers and angle brackets for extra strength. Just remember that nails hold better than screws going into end grain, the oposite is true going into side grain.

 

That all sounds very similar to how contractors constructed the supports for a neighbour's decking, except they drove lengths of 150 x 150mm preserved softwood into the clay subsoil (so perhaps piles rather posts?) then screwed the joists level all as above.