# Breeze block shed base supports



## Torx (19 May 2022)

Hi folks,

I’m designing a shed which will be 4.8 x 2.4m. I’m not planning to insulate the floor or anything, it’s mainly for storage although I might put a wood lathe in there at some point in the future. 

I was planning to put 3 rows of 5 paving slabs down below the framed base, but have come across people using breeze blocks (like below) which are cheap and easy to handle. Thoughts? What base, MOT? Depth? 







I’ve read some of the threads here about using 1m deep concrete piers etc. and it’s all made me a bit nervous about whether my approach will be enough, but I really need to make this just a shed and not over engineer it too much. 

I’m planning on using treated 2x3 for the floor construction followed by 18mm ply, walls likely the same with OSB / gap / featheredge. 

Tips appreciated!


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## Torx (19 May 2022)

Floor construction


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## John Brown (20 May 2022)

I doubt they are breeze blocks. More likely high density concrete.


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## John Brown (20 May 2022)

And I'm no expert, but my shed floor is 6 X 2. I very roughly followed Mike G's instructions. He doesn't post here anymore.


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## Jameshow (20 May 2022)

Torx said:


> Hi folks,
> 
> I’m designing a shed which will be 4.8 x 2.4m. I’m not planning to insulate the floor or anything, it’s mainly for storage although I might put a wood lathe in there at some point in the future.
> 
> ...


I'd go for 4x2 on blocks every 4ft apart. 

I'd dig out a shallow hole and fill with a weak concrete mix and then the block on top of it.


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## eribaMotters (20 May 2022)

I really would be thinking about insulating that floor as I'm sure you'll regret it at a later date. Look out for 2nd hand/damaged/offcuts of sheets on the likes of Gumtree, Facebook Marketplace, Preloved etc.





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## Jones (20 May 2022)

I would consider concrete lintels, these are dense concrete which will be better than light weight blocks and will be easy to level , the 3x4 ones will be quite cheap. Your floor design has a lot of superfluous timber, if you space the joists out to 400 centres it will be stronger and less bouncy, the noggins are doing nothing .


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## Torx (20 May 2022)

John Brown said:


> I doubt they are breeze blocks. More likely high density concrete.



You do seem to be able to buy some that are approved for use below a DPC, but you’re probably right 



John Brown said:


> And I'm no expert, but my shed floor is 6 X 2. I very roughly followed Mike G's instructions. He doesn't post here anymore.



I read Mikes thread, but 6x2 seems a bit overkill for this, since your average bought shed is 1 x 1 or something like that? 



eribaMotters said:


> I really would be thinking about insulating that floor as I'm sure you'll regret it at a later date. Look out for 2nd hand/damaged/offcuts of sheets on the likes of Gumtree, Facebook Marketplace, Preloved etc.
> 
> 
> 
> ...



I don’t plan to be working in there in cold weather, it’s basically for storage, are there other benefits to insulation? 



Jones said:


> I would consider concrete lintels, these are dense concrete which will be better than light weight blocks and will be easy to level , the 3x4 ones will be quite cheap. Your floor design has a lot of superfluous timber, if you space the joists out to 400 centres it will be stronger and less bouncy, the noggins are doing nothing .



I’ll look into those, thanks. I designed it to be made in smaller parts which I can fix together but perhaps it’s not worthwhile if I’m not gaining anything from the doubled up timbers. How do I make the noggins do something?


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## Spectric (20 May 2022)

Concrete blocks are cheap, or at least they were and so just bed these on mortar at regular intervals and don't overthink it which will lead to over engineering and increased cost.


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## morqthana (20 May 2022)

John Brown said:


> I very roughly followed Mike G's instructions. He doesn't post here anymore.


Not heard from since the tragic shed sinking incident?


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## Jameshow (20 May 2022)

I would just put one row of noggins in. 

Also the extra timber around the perimeter isn't needed tbh. You have the floor and then the wall plate which will be strong enough.


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## morqthana (20 May 2022)

You do know that Cheshire is full of animals as will love to take up residence under there? Foxes, rats...


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## okeydokey (20 May 2022)

However you build the concrete related base I would put some damp proof membrane between this and the wood to reduce the chance of moisture migrating into the wood.


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## Fitzroy (20 May 2022)

I built a 6x3m shed a few years back, build thread here, using concrete blocks (not breeze blocks) for the frame to sit on. I dug a hole below each one slightly larger than the block and rammed hardcore into it, the block sits on top, mortar would likely be better but harder work. I would not have been happy stacking multiple blocks without mortar between them. 

My base is 6x2 and I had a block roughly every meter. I don't know if it was insufficient support of poor workmanship but when I cam to lay the floor I found I had dips between the blocks and I had to addsome extra, see the post how. A 3x2 frame will just need more support points than a 4x2 or 6x2 frame. How many more I have no idea.

I placed DPM between the concrete blocks and the frame base as suggested.

I insulated the floor with glassroll and was told I'd made a rat heaven. Had no issue in 6years but my garden has 4' high solid granite walls and lots of cats with neighbours. Your milage may vary!

The method means the shed is not anchored down, but mine has not yet blownaway, again our garden is quite sheltered.

Fitz.


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## Jones (20 May 2022)

Concrete blocks will be ok but I suggested lintels or fence posts as they're denser so will be less prone to rising damp and will be easier to level up. Noggins or strutting in floors are needed to stop joists capsizing if the joist is tall relative to its width and the span is over 2.5 m which yours is not so no noggins required. A glance at the span tables shows a 2x5 can do a 2.4 m span either c16 or c24 grade which would mean you can miss out the centre block support, might be worth considering the cost/ effort difference. I would use class 3 treated or better class 4 for the base and put a small piece of dpc or slate under the joists where they sit on the support.


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## Torx (20 May 2022)

Jameshow said:


> I'd go for 4x2 on blocks every 4ft apart.
> 
> I'd dig out a shallow hole and fill with a weak concrete mix and then the block on top of it.





Spectric said:


> Concrete blocks are cheap, or at least they were and so just bed these on mortar at regular intervals and don't overthink it which will lead to over engineering and increased cost.



Like these? 






Tarmac Standard Dense Block - 7.3N 100mm | Wickes.co.uk


Tarmac Standard Dense Block - 7.3N 100mm




www.wickes.co.uk







morqthana said:


> You do know that Cheshire is full of animals as will love to take up residence under there? Foxes, rats...



Can’t see what I can do about that, same as all sheds? I like foxes and I’ve got a cat…



Fitzroy said:


> I built a 6x3m shed a few years back, build thread here, using concrete blocks (not breeze blocks) for the frame to sit on. I dug a hole below each one slightly larger than the block and rammed hardcore into it, the block sits on top, mortar would likely be better but harder work. I would not have been happy stacking multiple blocks without mortar between them.
> 
> My base is 6x2 and I had a block roughly every meter. I don't know if it was insufficient support of poor workmanship but when I cam to lay the floor I found I had dips between the blocks and I had to addsome extra, see the post how. A 3x2 frame will just need more support points than a 4x2 or 6x2 frame. How many more I have no idea.
> 
> ...



Thanks, that’s an amazing build I’m working my way through the thread. I think the price of cladding like that at the moment is out of my budget but it looks lovely. This is a bit of a practise run for a second building which Id like to think would be a similar style. 



Jones said:


> Concrete blocks will be ok but I suggested lintels or fence posts as they're denser so will be less prone to rising damp and will be easier to level up. Noggins or strutting in floors are needed to stop joists capsizing if the joist is tall relative to its width and the span is over 2.5 m which yours is not so no noggins required. A glance at the span tables shows a 2x5 can do a 2.4 m span either c16 or c24 grade which would mean you can miss out the centre block support, might be worth considering the cost/ effort difference. I would use class 3 treated or better class 4 for the base and put a small piece of dpc or slate under the joists where they sit on the support.



Good tips, thanks. I think I’ll go back to the drawing board this weekend!


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## Jameshow (20 May 2022)

Yes like those Wickes ones...


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## morqthana (20 May 2022)

Torx said:


> Can’t see what I can do about that, same as all sheds? I like foxes and I’ve got a cat…


Do you like the smell of foxes?

Pressure treated timber, or composite decking boards, at ground level, screwed into the blocks, fill in the gap between those and the frame with perforated aluminium sheet, galvalnised expanded metal etc. Basically anything that will keep ventilation but won't be chewed through by vermin.


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## JimMc (21 May 2022)

There is an old method ( rule of thumb) for sizing floor and roof timbers. It’s take the span ( in feet ) and half it, add 2 and thats the depth in inches. For roof rafters take the span in feet and that’s the depth of timber you need.
For example, If your floor timbers are spanning 6 feet then you need a joist to be (1/2 of 6 = 3 plus 2 ) ie 5 inches by 2 inches.
if you are sizing timbers for your flat or pitched roof then for an 12 feet span you will need (1/2 of 12=6) a 6 by 2 inch timber.

Put in insulation, it’s easy to do at this stage, is not expensive and worth it for storage. Think condensation. You can drape rolled insulation ver the timbers and just nail the flooring on top. This future proofs the shed, if not for you then for a future owner. 
Hope this helps.


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## Torx (21 May 2022)

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?


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## JimMc (21 May 2022)

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.


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## IBmatty (21 May 2022)

Torx said:


> 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.


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## JimMc (21 May 2022)

IBmatty said:


> 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.


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## Bob Chapman (21 May 2022)

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.


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## morqthana (21 May 2022)

JimMc said:


> 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.


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## Torx (21 May 2022)

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.


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## Torx (22 May 2022)

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.


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## JimMc (23 May 2022)

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


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## BucksDad (23 May 2022)

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


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## Humf (31 May 2022)

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.


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## JimMc (31 May 2022)

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.


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## Humf (31 May 2022)

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.


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## JimMc (31 May 2022)

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!


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## flying haggis (1 Jun 2022)

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.


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## Humf (1 Jun 2022)

JimMc said:


> 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.


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## Spectric (1 Jun 2022)

Humf said:


> 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.


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## Humf (1 Jun 2022)

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.


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## Jameshow (1 Jun 2022)

Humf said:


> 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.


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## Humf (1 Jun 2022)

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


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## Jameshow (1 Jun 2022)

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?


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## Humf (1 Jun 2022)

Jameshow said:


> 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?


Yep gotcha. A block work pillar sounds a lot easier than mixing and filling form work. I like it


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## morqthana (2 Jun 2022)

It's on sloping ground. You could use the strongest, least falley-over pillars known to man, and you still risk the whole lot sliding downhill without some sort of piling or deep footings.

Cut and fill to level the site, and retaining walls?


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## Humf (2 Jun 2022)

I should really start a new thread but just briefly, the ground is mainly rock. The word is in our address and I’ve read that a nearby cathedral was built using stone from a nearby quarry. 

But you are still making me doubt myself…!


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## Jameshow (2 Jun 2022)

morqthana said:


> It's on sloping ground. You could use the strongest, least falley-over pillars known to man, and you still risk the whole lot sliding downhill without some sort of piling or deep footings.
> 
> Cut and fill to level the site, and retaining walls?


So long as the pillars are cut into the rock / shale etc and not leaning I don't see how it can fall down the hill. 

If your worried about it slipping drill some holes through the blocks and drive rebar into the hard ground.


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## morqthana (4 Jun 2022)

Jameshow said:


> So long as the pillars are cut into the rock / shale etc and not leaning I don't see how it can fall down the hill.


I sort of got the idea that he was planning blockwork pillars on the normal sort of footings you'd use on level ground for a normal shed.

Apologies if that's not the case.


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