Having trouble building a shed base.

Mark A · 16 Mar 2012 at 13:12

Hi,

I am having a bit of trouble building a shed base. I decided on a 2" x 4" pressure treated frame, but I was going to sit this onto piers to lift it off the ground. Only trouble is that I have bought medium density concrete blocks, that I have now found out wont do as they crumble over time :/.

I bought ballast and cement to make concrete and was going to dig out 8 holes, 4 each side, then put the blocks onto the concrete pads. Then sit the timber frame on top of this.

Is there anything else I could do? I don't really want to spend any more money on this if possible. I'd also like to use the blocks up some how. Maybe smash them into hardcore?

The shed is fairly large at 10' x 8' and the site its going on is turf at the moment, with clay soil under.

TIA

touch · 16 Mar 2012 at 13:24

Is there a reason for having it off the ground?

When we put up our shed, we had it sitting straight on a base of paving slabs.

Gregster · 16 Mar 2012 at 13:28

I built my shed from 305cm lengths of 14cm x 3cm. I leveled the ground and placed 12 patio slabs down and built the base on that. They keep it nicely off the ground.

Hagar · 16 Mar 2012 at 13:33

Keep to your plan,

bed and render the blocks in sand cement mortar 1/2" all round, this will weatherproof them. Some old quarry tiles on top or a thin steel plate to provide a bearing and spread the load.

anything I don't mind · 16 Mar 2012 at 13:36

I was always taught to put that black thick plastic sheeting down under concrete/cement/stones/paving etc.

Gregster · 16 Mar 2012 at 13:42

groen said:
I was always taught to put that black thick plastic sheeting down under concrete/cement/stones/paving etc.

Yes Sir. I did this.

Mark A · 16 Mar 2012 at 13:47

I was going to go for paving slabs but with the soil being heavy in clay I was advised I would have had to put a thick layer of hardcore down. So that would mean a lot of digging out, having to get rid of the topsoil, having to buy a lot of hardcore and then having to buy the paving slabs. Would have also had to hire a wacker to compact it and my local tool hire charge £45 for the day.

Just seemed simpler, cheaper and quicker to use pier foundations and a timber frame. Just wish I had read up properly and got a suitable material for the piers.

Keep to your plan,

bed and render the blocks in sand cement mortar 1/2" all round, this will weatherproof them. Some old quarry tiles on top or a thin steel plate to provide a bearing and spread the load.

That's a good idea. I didnt think about rendering them. I dont have any materials for on top to spread the load though, so If I have to go and buy something I may as well just buy bricks or something and use them instead.

One Idea I did have was to dig out a trench the same size as the timber frame. Then fill it with the all in ballast that i ordered to make the concrete. Then sit the Timber frame onto the ballast. That way the ballast would provide drainage so the timber isnt sitting on damp ground.

The timber is pressure treated so should last a while before it starts to rot. I do also have some pvc trim that i could nail to the under side to help stop water getting to the timber.

Would this work?

Hagar · 16 Mar 2012 at 14:34

Mark A said:
.

One Idea I did have was to dig out a trench the same size as the timber frame. Then fill it with the all in ballast that i ordered to make the concrete. Then sit the Timber frame onto the ballast. That way the ballast would provide drainage so the timber isnt sitting on damp ground.

The timber is pressure treated so should last a while before it starts to rot. I do also have some pvc trim that i could nail to the under side to help stop water getting to the timber.

Would this work?

My shed, not as big as yours at 8' x 6' sits on a 4" x 2" treated (tanalised)timber frame on ballast so that the base of the frame is at ground level. This has worked for about 8 years. The shed floor is 4" above the ground. We had the same ground, thick clay. I placed a 6" layer of ballast, then levelled the frame on blocks, then tamped ballast around the frame and blocks using a 4" x 2" pole with a piece of 9" x 3" nailed to the end

Frozennova · 16 Mar 2012 at 14:45

Our 12x10' metal ship lap shed sits on a 6" concrete base with 4" of hardcore, base is around 14x12' iirc. bit overkill but it does the job and we'll never have to worry about it going anywhere

Mark A · 16 Mar 2012 at 15:07

nkata said:
My shed, not as big as yours at 8' x 6' sits on a 4" x 2" treated (tanalised)timber frame on ballast so that the base of the frame is at ground level. This has worked for about 8 years. The shed floor is 4" above the ground. We had the same ground, thick clay. I placed a 6" layer of ballast, then levelled the frame on blocks, then tamped ballast around the frame and blocks using a 4" x 2" pole with a piece of 9" x 3" nailed to the end

Thanks. I might give this a shot then. If the worse comes to the worst it wont be too hard or costly to replace the treated timber frame if it did rot.

My old shed was just sat on red bricks, directly on top of the soil and that lasted a good 15 years

. It was a lot smaller though at about 5' x 8'.

j.col · 16 Mar 2012 at 16:18

a good tip, even though the base of the shed is already pressure treated, i always give it another coat of fence paint, its not going to be seen.

Mark A · 16 Mar 2012 at 16:31

j.col said:
a good tip, even though the base of the shed is already pressure treated, i always give it another coat of fence paint, its not going to be seen.

Thanks. I have some Ronseal shed and fence treatment. I was wondering if you could use that over the top to add more protection, so its good to know you can. The shed I have bought is also pressure treated so I'll probably give that a coat as well.

Tom0 · 16 Mar 2012 at 16:41

Here is a shed me and mate built from scratch last year on a base, granted it was easier because we had slabs to build on but could get the same base with hardcore/rubble to keep things level and such.

Edit: Sadly I don't have a picture of the completed thing.

kwerk · 16 Mar 2012 at 17:40

I would do 4 concrete piers using sonotube forms and strongtie connectors, like this:

http://www.shedking.net/shed-foundation-piers.html

I've built a deck that way and it's fairly easy to do by yourself with a post hole digger and wheel barrow. Just make sure you get the forms square and level and that the concrete goes down below the frost line.

When I built mine I did total over kill but my deck is about 1000 sq.ft.
Rented a tow behind hydraulic auger (great fun, cuts like butter).
Holes dug 4-1/2 feet deep, wider at the bottom than top.
12" sonotube forms.
Few inches of gravel at the bottom.
Rented a cement mixer, ended up mixing about 100+ 80lb bags uggg
Stuck 2 pieces of 1/2" rebar vertically in each pier.
Set some massive hot dipped galvanized J-bolts in the middle of each pier before it set.
Attached 6x6 posts with HDG strongtie post bases.

It's solid as ****.

Mark A · 16 Mar 2012 at 17:41

Tom0 said:
Here is a shed me and mate built from scratch last year on a base, granted it was easier because we had slabs to build on but could get the same base with hardcore/rubble to keep things level and such.

Edit: Sadly I don't have a picture of the completed thing.

That is one strong base! Looks great.

Hmm, that gives me an idea. What if I was to dig the holes for the concrete pads. Then make up some 1' square by 4" timber frames and sit them on top of the holes, then fill in the concrete up to the top of the timber. So it would be just like using the concrete blocks but it would be solid concrete instead of the blocks.

Would I be able to smash up the concrete block to use as hardcore?

Arnie · 16 Mar 2012 at 17:42

I like the base, I like the brickery, concrete base.

Mark A · 16 Mar 2012 at 18:09

kwerk said:
I would do 4 concrete piers using sonotube forms and strongtie connectors, like this:

I think what I'm planning to do is similar to this, albeit on a much smaller scale.

Something i just noticed in that article:

I always suggest that buyers of my storage shed plans check with their local building inspector to make sure which method of anchoring your shed floor is acceptable in your particalar locality.

Do you have to get planning to build a shed in the states?

bitslice · 16 Mar 2012 at 18:49

As long as the base is kept dry, out of standing water and well ventilated it should be good for 10 years at least.

kwerk said:
I would do 4 concrete piers using sonotube forms

I see Americans using these all the time and they are such a great idea, pier foundations are a much more efficient use of concrete, but does anybody know where I can get Sonotubes in the UK/Staffordshire?

kwerk · 16 Mar 2012 at 19:44

bitslice said:
As long as the base is kept dry, out of standing water and well ventilated it should be good for 10 years at least.

I see Americans using these all the time and they are such a great idea, pier foundations are a much more efficient use of concrete, but does anybody know where I can get Sonotubes in the UK/Staffordshire?

You could probably use a thick cardboard postal tube if you packed the earth around it before you pour so it didn't burst. You probably have to coat the inside with grease or something so the cardboard doesn't suck the moisture out of the concrete as it's setting. That's all a sonotube is, basically a waxy cardboard tube. 8" piers are big enough for a shed I'd think.

Fuzz · 16 Mar 2012 at 20:27

cut bottom out of a bucket.
Dig holes for you piers
Fill hole with concrete mix
When filled to ground level place bucket upside down over hole and continue to fill.
Level off at required datum height.
Repeat for other piers until complete

Having trouble building a shed base.

Wise Guy

Wise Guy