Some basic building advice needed ?

[tigler]

Am rebuilding an Octagonal summer house in my mums garden and have a slight problem.
It's being re-assembled on a base topped with concrete slabs layed on concrete. I was being helped by a guy with building the base and as it happened he layed the slabs, a while ago now, when I wasn't there.
Now I come to look at them in detail they haven't been layed very level ! The surface undulates by about as much as 3/4" !
As we want to improve the summer house this time I am putting in a floor, made from 20mm shuttering board, this will need joists which will be resting on the slabs, which aren't level !! And there is my problem, how to create a level surface for the joists to rest on.
One idea I have is to lay bricks on the slabs in short runs of 2 or 3 to act as supports for the joists. They could be levelled up with mortar ? Would that work ok ? Although there is little load on the floor I'm a bit concerned that the mortar may break up over time and the joists would lose the support.

The only other solution I've come up with is to lay the joists with a slight gap under them and cut packing to suit. Time consuming that one though !

Another issue I'd appreciate advice on please, originally the structure was just resting on a hardwood plinth around the edge, this has started to rot. This time I'm going to use a course of bricks to act as the plinth, what is the best mortar / cement to use to prevent the bricks loosening over time ? It will be a single course layed directly on the slabs.

 

[rtbcomp]

I'd use bits of slate &c on top of a membrane to pack the joists, this should keep them dry and allow a bit of air to circulate.

 

[MarkMG]

try these http://www.screwfix.com/search.do;jsessionid=VKdXTjZRkYZ1p5HdQnkp7yfRFH8QxNCv92nZ1gqwDS1mvFwS2p1s!-1693905658?fh_search=plastic+shims

 

[Windy Miller]

I think I'd go for the brick option - like a really small dwarf wall. Find the highest point and set a brick on a fairly stiff (about 4:1) mortar base. Set that as your datum point and level off that to all the other bricks.

When everything has dried out nicely lay your joists on top of strips of DPC, and nail/screw short lengths of timber in between the joists to stop them twisting. This should prevent anything moving about and breaking up the mortar, although a stiff mix like this is likely to be stronger than the brick anyhow! Something like this:

http://www.photographersdirect.com/buyers/stockphoto.asp?imageid=820254

That should give the floor a nice solid feel without the bounce that you find in a cheap shed.

 

[Robotstar5]

I did what's been suggested to put an 8x6 shed onto slabs. Mortared a brick on the highest point and levelled the rest to it using slate as packers then 3x2 tannelised timber to support the shed. Hasn't moved in 7 years

 

[Jack]

i would use the plastic packer option, much quicker than trying to level with a course of bricks

 

[mike os]

depends if you want to raise it up that much... bricks looking at 75mm over the highest point.

slate or plastic packers is simplest... use a bit of silicone or mortar to hold them in place.

 

[the snooper]

is the base bigger then the summer house ?
if so the joists will need raising anyway so as not to soak up water when it rains, i think i would go for the bricks as it provide ventilation for the joists and a means to stop the water