base for lean to shed

[Jupiter01]

I have now started designing this lean to shed and based on responses to another post on the roof construction, I am now able to increase the length of this shed to 4.5 metres. The depth will still be around 60cm. I like the idea of the concrete posts but wanted to check if there is something similar which is not too chunky (as I will be losing space inside) and something I can cut with my 4.5 inch grinder. Given the length, I think I will need to place these concrete supports along the 60cm depth, running from the house wall to the end of the base, rather than across the 4metres length. Also, when levelling these concrete posts (or whatever I go with) can I use plastic spacers to level them?

Thanks for your support.

 

[cwhaley]

I have now started designing this lean to shed and based on responses to another post on the roof construction, I am now able to increase the length of this shed to 4.5 metres. The depth will still be around 60cm. I like the idea of the concrete posts but wanted to check if there is something similar which is not too chunky (as I will be losing space inside) and something I can cut with my 4.5 inch grinder. Given the length, I think I will need to place these concrete supports along the 60cm depth, running from the house wall to the end of the base, rather than across the 4metres length. Also, when levelling these concrete posts (or whatever I go with) can I use plastic spacers to level them?

Thanks for your support.

You could use any concrete post, railway sleeper, treated fence post (they will rot, but not for at least 10 years). I would honestly go for the concrete posts -- they will provide a very strong, permanent base for the shed which will be stable and secure and importantly, free from rot!

The PVC spacers look good, but they are small and won't raise the shed high enough. You'll get splash back up the side of the shed and even worse, it'll provide a nice low gap for rats to build nests in. The gap provided by the posts will be too high and open for a rat to want to nest in.

Yes you can use plastic spacers, but I'm not sure they're UV-proof? I'd check that, otherwise they'll go brittle and snap. Alternatively you could use sand/cement, slate, etc.

I'm still trying to find the picture of the base, but I think it was taken on a different phone and iCloud hasn't saved it! We had laid a large area of 3' x 2' "council slabs" and on top of that, concrete fence posts, perpendicular to the joists on the bottom of the shed. The shed is essentially a workshop and we have no concerns over the floor with it being done that way.

 

[Jupiter01]

Some follow-up questions please:
- Can these posts be cut to size using the grinder that I have?
- Can I use plastic spacers to level these or do you recommend something else?
- What size timber should I use for the frame underpinning the OSB base? Trying to understand how far off the ground the eventual floor will be.

Thanks again

 

[Harry Bloomfield]

The depth will still be around 60cm. I like the idea of the concrete posts but wanted to check if there is something similar which is not too chunky (as I will be losing space inside) and something I can cut with my 4.5 inch grinder.

Scaffold poles, maybe alloy ones?

 

[cwhaley]

Some follow-up questions please:
- Can these posts be cut to size using the grinder that I have?
- Can I use plastic spacers to level these or do you recommend something else?
- What size timber should I use for the frame underpinning the OSB base? Trying to understand how far off the ground the eventual floor will be.

Thanks again

Yes they can be cut with a grinder if you have the suitable disc size and type, however why not buy 10ft posts? This will cover the whole length of your shed (at 3m long). At 60om wide, you could probably just use two posts -- intermediate posts are about 10cm wide so you would only have an unsupported span of 40cm.

If you can find shims (rather than spacers) which would be okay outside, then go for it. Most plastics degrade in contact with UV light, that's why I suggested something else. For me I would feel comfortable laying them all on a bed of sand and cement, tapped into place level.

I would just use 2" square (2x2) timber. This is readily available.

The posts will give you a nice air gap, the 2x2 will give you a nice solid frame to mount the floor on and you'll have a nice solid dry shed.

 

[Jupiter01]

This will cover the whole length of your shed (at 3m long)

I am now planning to go 4.5 metres and hence considering to run the posts in the other direction.

 

[cwhaley]

I am now planning to go 4.5 metres and hence considering to run the posts in the other direction.

Sorry if you stated that and I missed it!

The intermediate posts can definitely be cut down with a grinder. If not those, maybe look at lintels. Ones that width would only have a single rebar in the middle.

 

[Jupiter01]

This might be better as it's flush all around and 65mm tall.

Expamet Concrete Lintel, (L)2100mm (W)100mm | DIY at B&Q

Use this pre-stressed reinforced concrete lintel 2100mm x 100mm to optimise single wall applications.

www.diy.com

 

[Odds]

How will it cope with standing water under the shed - is there a gradient to allow for run-off?
Can you take up the existing slabs, cut them to size, and use an EcoGrid Bloxx instead?

This helpful chap shows how...

 

[Jupiter01]

How will it cope with standing water under the shed - is there a gradient to allow for run-off?
Can you take up the existing slabs, cut them to size, and use an EcoGrid Bloxx instead?

This helpful chap shows how...

There's a definite slope away from the house with the existing concrete path. Hence the questions, about how I level the concrete lintels that the shed will be resting on. Standing water should not be an issue I think. I wasn't planning to mechanically fix the base to the lintels or the floor but the frame built on it will be anchored to the wall as will the lean-to roof section. I think that should be adequate?

 

[Jupiter01]

I would just use 2" square (2x2) timber. This is readily available.

Do you think 2x2 is also adequate for the studwork and roof rafters? As you know its only around 60cm wide and will be wrapped with plywood and some sort of cladding. I want to preserve internal space as much as I can.

 

[Odds]

There's a definite slope away from the house with the existing concrete path. Hence the questions, about how I level the concrete lintels that the shed will be resting on. Standing water should not be an issue I think. I wasn't planning to mechanically fix the base to the lintels or the floor but the frame built on it will be anchored to the wall as will the lean-to roof section. I think that should be adequate?

If you place concrete posts around the shed then water will collect against them, according to the gradient of the slope, surely. The solution to that is to support the corners and leave a gap along the sides, allowing water to flow away beneath the shed.

 

[Jupiter01]

If you place concrete posts around the shed then water will collect against them, according to the gradient of the slope, surely. The solution to that is to support the corners and leave a gap along the sides, allowing water to flow away beneath the shed.

I was planning to (hadn't considered your very important point re. flow of water) have the concrete lintels running along the 60cm width. This is also the direction of the slope.

 

[Odds]

I was planning to (hadn't considered your very important point re. flow of water) have the concrete lintels running along the 60cm width. This is also the direction of the slope.

If you're not planning to store anything heavy in there then support for the corners should be sufficient. You can add a central support if you think the floor needs it.

 

[Jupiter01]

If you're not planning to store anything heavy in there then support for the corners should be sufficient. You can add a central support if you think the floor needs it.

There will be a fair amount of power and hand tools. My chop saw weighs a chunk on its own!
Also, the floor is around 4 metres in length and I want to make sure it doesn't bow over time. Perhaps I should put in a few concrete lintels across that 4 metre length (but running in the direction of the slope).

I was going to build the shed floor with an OSB board mounted on a 2x2 frame as per earlier suggestion.

Please let me know if you think any different.

Also, can I please have some guidance on the timbers I need to use for the upright and rafters. The shed is only around 60cm wide and I want to maximise the space inside.

Thanks for the support.