Breeze block shed base supports

[JimMc]

No. If you are using 4by 2 then they will only span 4feet between supports.
Between the timber and the support ( concrete block of paving slab) there should be a DPC ( damp proof course) this stops the timber getting wet and rotting.

 

[IBmatty]

I’m being persuaded on the insulation, even if I just do floor. With a 50mm air gap below the floor joists using 4x2 is there any reason not to insulate the full depth of the joist?

I don’t think you’ll regret insulating the floor be it the full depth of the joist or not (no reason not to btw). I built a 5m x 3m shed for storage near 20yrs back. Used concrete blocks as you question and it‘s been fine, no movement at all and there is a lot of weight in there. Built a small attached but separate extension to it a couple of years back with the only difference being I didn’t insulate the floor…just straight to OSB. Condensation..lots of it! Moist air coming up through the floor. Last summer I rebuilt the floor as with the original - 40mm polystyrene board, vapour barrier and then refit the OSB. Condensation problem solved for an extra 30 euros.

 

[JimMc]

I don’t think you’ll regret insulating the floor be it the full depth of the joist or not (no reason not to btw). I built a 5m x 3m shed for storage near 20yrs back. Used concrete blocks as you question and it‘s been fine, no movement at all and there is a lot of weight in there. Built a small attached but separate extension to it a couple of years back with the only difference being I didn’t insulate the floor…just straight to OSB. Condensation..lots of it! Moist air coming up through the floor. Last summer I rebuilt the floor as with the original - 40mm polystyrene board, vapour barrier and then refit the OSB. Condensation problem solved for an extra 30 euros.

Bang on, learn from other peoples mistakes not your own.

 

[Bob Chapman]

Torx my shed is only 6ft x 4ft, so nowhere near as big as yours, but I did exactly what you are suggesting. Breeze blocks at each corner. It's on a very slight slope so the number of breeze blocks varies from one to three in order to get them to the same level. Only soil underneath them, DPM on top of the blocks then a wooden framework (roughly 3in x 3in) and shed on top. It's been there three years now with absolutely no problems. Make of this what you will but I'd beware very expensive (in terms of cash or labour) solutions. Good luck, whatever you decide.

 

[morqthana]

Bang on, learn from other peoples mistakes not your own.

If it's true that you learn from your mistakes I've had the most fantastic education.

 

[Torx]

A bit of playing around trying to take everyone's advice on board...it seems there are many ways of doing this.

I'll upgrade to 2 x 4 timbers and will insulate too if I can get it cheap enough.

1. Built in situ. Could build it on the blocks I suppose. I don't like how every other noggin would miss supporting the edge of the boards, but probably my OCD.

2. Build in two large chunks...for some reason I like the heavy duty feel of doubling up the timbers in case I change my mind about the intended use in the future.

3. Build in 4 chunks. I like this the best as I can't get anything done quickly and it's likely to go together over several weeks.

@Fitzroy you seemed to think building in this fashion might be an issue and did it from outside in? Why was that?


Any comments - strength, ease of assembly, positioning of blocks etc?

Thanks.

 

[Torx]

Another 15 minutes of playing around in 2D today while getting the kids off to sleep...

Not sure how to work out the roof pitch, but that sort of looks right?

I've got questions about windows (above inspired by @Fitzroy again). Is it worth doing a build thread or are you lot bored of them? It won't be anything like the standard of some I've seen on here.

 

[JimMc]

Variation 3 is better. In 1 and 2 the joist spans are too big.

 

[BucksDad]

Build threads are always appreciated... every build is different and new builds bring up new discussions / new topics. Links to products used from a thread in 2014 probably don't work anymore so a 2022 build with up-to-date links is always good... and a forum needs new interesting content to keep it interesting

 

[Humf]

Quick question for those in the know…

Is there a max size building that this type of base can be used for? I notice MikeG in his ‘no concrete’ thread says only to be used upto 20m2 I think.

 

[JimMc]

It all depends on the soil, you need a firm base and consistent bearing pressure.
there will be some settlement of the supports but it’s not so much about the amount of movement but that it is the same at all supports. if you get differential settlement then it can cause problems in the structure. Less important in a shed than say a brick or block building.
so my answer would be “ no max size but consider the ground and firmness of the soil. If it was a very soft silty clay than you might want to make the supports larger.”
Most soils below the topsoil are more than adequate for small building never mind sheds.
Hope this helps.

 

[Humf]

Very helpful thanks. I live in the Cotswolds and our ground is virtually rock. Removing it to then replace with type 1 always feels expensively wasteful. You end up removing well compacted stone and grit, only to replace with the same.

 

[JimMc]

Hi, on the soil you’ve got there will be no settlement. Any size you like.
I once had to design a post office garage in Lairg. A long way from Edinburgh.
Travelled up the night before. Met a jcb ( -10, jcb pipes froze while travelling) and eventually tried to dig some trial pits, the bucket hit Rock at 75mm. Bit of a waste of 2 days and the hire cost. I was quite young!

 

[flying haggis]

If you go with building in four sections you could fix chicken wire to the underside (fix to top then flip over...!) screw sections together, then lay roll insulation over the chicken wire then fit a floor.

 

[Humf]

Hi, on the soil you’ve got there will be no settlement. Any size you like.
I once had to design a post office garage in Lairg. A long way from Edinburgh.
Travelled up the night before. Met a jcb ( -10, jcb pipes froze while travelling) and eventually tried to dig some trial pits, the bucket hit Rock at 75mm. Bit of a waste of 2 days and the hire cost. I was quite young!

I’ve had a mini digger in this garden a few times. Grading the driveway was just about ok but further up in the garden I’ve worked on ground which really needed a breaker attachment. Without it the whole thing was lifting quite controllably off the ground.

On the topic of my base, I have approx 400mm of fall from front to back. I’m nervous of stacking blocks so exploring the idea of creating concrete pillars using twin core drainage pipe to cast them. Saw it being done by Liam of Oakwood and looks good.

 

[Spectric]

On the topic of my base, I have approx 400mm of fall from front to back. I’m nervous of stacking blocks so exploring the idea of creating concrete pillars using twin core drainage pipe to cast them.

I am not sure why you are nervous of stacking blocks, that is the way walls and such are made but if you want another option then just make some shuttering for each of the required pillars and fill with concrete, much easier and stronger than trying to cast objects not in situ using drainage pipe.

 

[Humf]

Yes I know you’re right. I’m in danger of over thinking and introducing unnecessary complications. I guess my thinking was that without achieving depth for the higher piers (with solid ground being hardwork) I could instead gain some width. Btw - the pipe is placed in position and then filled with concrete mixed on-site. So essentially form work rather than cast. Some timber shuttering I’m sure would achieve similar.

 

[Jameshow]

I’ve had a mini digger in this garden a few times. Grading the driveway was just about ok but further up in the garden I’ve worked on ground which really needed a breaker attachment. Without it the whole thing was lifting quite controllably off the ground.

On the topic of my base, I have approx 400mm of fall from front to back. I’m nervous of stacking blocks so exploring the idea of creating concrete pillars using twin core drainage pipe to cast them. Saw it being done by Liam of Oakwood and looks good.

400mm is only the length of a block so you will be making perfect squares, so you would only need 8 blocks per Pillar that is next going to fall over. If worried cement it together.

 

[Humf]

Belly down, just 4 needed? Sorry I might be misunderstanding…

 

[Jameshow]

You could just put 4 belly down.

I was thinking pillars 2 blocks belly down an 2 going perpendicular etc.

A few more blocks isn't going to make much difference surely?