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Workshop decking

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Workshop decking

Postby DomD » 31 May 2021, 15:47

Hello all,
This is my first post here over from UKW where most of my workshop build is. I thought I'd make this thread here as it seems to be more active for workshop builds now.

While my workshop is mostly complete, I intend to build a deck outside to make working outside possible and to store a water butt on the left side.

This is the current state of the workshop:
Image

And this is my decking plan so far:
Image

I am going to try and keep all the timber 150mm off the ground which will mean some excavation but will hopefully increase the longevity of the frame.

Lots of decks I've seen use timber posts cast into concrete/postcrete as supports; I can't imagine this will last very long so instead was planning to use brick/block piers - this is the area where I am most uncertain.
My initial thoughts are to do something along these lines:
Image
With DPC between the timber and the mortar capping. I'm not convinced this is the best way of doing it so would appreciate any thoughts.

Many thanks,
Dom

P.S. Also wanted to thank everyone that has posted workshop builds on here as they were really useful to look through during my build!
Last edited by DomD on 29 Jun 2021, 14:12, edited 1 time in total.
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Re: Workshop decking - Foundation piers query

Postby Mike G » 31 May 2021, 16:32

Hi Dom. Good to see you over here.

Before answering your question, I'd just say that for a little column like the one you are proposing, you could use concrete without Type 1, or Type 1 without concrete. You really don't need both.

Personally, I doubt I would be laying any bricks. I'd probably do a steel shoe/ bracket thing direct to the concrete. I might even cast concrete columns in an upside down plastic container, or ply former. Then I'd be looking for something to space the timber off the concrete. This could be something as unsophisticated as some pieces of slate or a cut-out from a piece of plastic pipe. There is probably some expensive proprietry thingamejig.
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Re: Workshop decking - Foundation piers query

Postby DomD » 31 May 2021, 20:41

Hi Mike - glad to hear from you :)

The reason I was thinking of doing brick piers is because 2m in front of the workshop is quite a steep slope:
Image

And my plan was to vary the height of the brick piers based on their location. Most will be similar in height except the one in the corner:
Image

I'm not sure if it would be feasible to form such a tall concrete post in this corner location to rest the frame directly on - though in the other areas it may be easier. Additionally, I'm not sure I'm going to close off the deck front so would rather bricks were visible than concrete.

I think if I were to pick one of type 1/concrete I might pick concrete for peace of mind and because it will give me a stable surface to lay bricks on - which would you recommend for this type of pier?

Many thanks,
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Re: Workshop decking - Foundation piers query

Postby Mike G » 01 Jun 2021, 07:06

Ah, right......I remember now. Then brick is your best choice, at least for the visible piers.
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Re: Workshop decking - Foundation piers query

Postby BigMonka » 01 Jun 2021, 22:00

Might be worth noting that, in general, a decking over 300mm high requires planning permission. I only found that recently before I built my decking and was surprised how low it was especially when you think of the height of the joists and deck boards being a decent proportion of that.
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Re: Workshop decking - Foundation piers query

Postby 9fingers » 02 Jun 2021, 08:22

As you are building brick piers I’d add one to come up through the deck to support the water butt. It takes a hefty point load off the decking and the risk of water being trapped beneath the butt and rotting the timber.

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Re: Workshop decking - Foundation piers query

Postby DomD » 03 Jun 2021, 18:24

9fingers wrote:As you are building brick piers I’d add one to come up through the deck to support the water butt. It takes a hefty point load off the decking and the risk of water being trapped beneath the butt and rotting the timber.

I definitely need to strengthen the deck in this area but fortunately, as it will be in the corner (just above 'A' in my diagram), its already going to almost directly under a pier / between a pier and the wall plate. I was hoping an extra joist or two would be enough.

I don't really like the look of plastic water butts so was thinking of getting an oak barrel style one - the deck side is sized so it would fit with the tap overhanging the edge for easy watering can filling. Hopefully with some potted plants along the deck the left side of the workshop will look a bit nicer.

BigMonka wrote:Might be worth noting that, in general, a decking over 300mm high requires planning permission. I only found that recently before I built my decking and was surprised how low it was especially when you think of the height of the joists and deck boards being a decent proportion of that.

I vaguely remember this from when I was looking into planning permission for my shed so thanks for reminding me. I believe this is measured from the highest ground level point around the structure so hopefully I am alright but I'll check the regulations again.

Thanks for all the advice so far,
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Re: Workshop decking - Foundation piers query

Postby DomD » 03 Jun 2021, 19:24

Mike G wrote:Ah, right......I remember now. Then brick is your best choice, at least for the visible piers.


Great - this is what I think I'll do for all of them as the area below the deck will be partially visible at all sides.

I drew out another pier detail which might be closer to what I actually do given I don't need both type 1 and concrete:
Image

I am hoping one brick piers will be sufficient at the spacing I've chosen. As you suggested I've drawn in slate at the top but was unsure how I would fix the joists to the piers. Maybe some galvanised strapping set into the brickwork?

I want to avoid having to dig down to subsoil if at all possible as it is ~60cm below the surface (this area was originally a slope and has been backfilled). Can these concrete pads just be poured on compacted topsoil or would that be inadvisable?

Thank you for your help,
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Re: Workshop decking - Foundation piers query

Postby DomD » 13 Jun 2021, 16:06

I have now cleared out the area around the shed so the deck will have a 150mm void below it. I plan to cover this area in a weed control fabric and bark (to match a lower area of the garden).
Image

The joists will need to be 5x2 rather than 6x2 so when a deck board is added it is at the level of the doorway.

The subsoil is ~0.7m below the surface which means with a 150mm concrete pad at the bottom I would need an 11 course brick plinth to support the deck. I could always pour more concrete to reduce bricklaying time - a full wheelbarrow should almost fill up the hole leaving only a few bricks to lay.

Image

I will hopefully get started on this soon but first need to install some guttering and underground pipe.
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Re: Workshop decking - Foundation piers query

Postby 9fingers » 13 Jun 2021, 16:53

Hot work if you’ve been doing that today!

Coming on
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Re: Workshop decking - Foundation piers query

Postby DomD » 15 Jun 2021, 20:37

9fingers wrote:Hot work if you’ve been doing that today!

Yes, fortunately there is some shade up there but its 28C tomorrow when I'm panning on digging the rest of the holes :|

When digging the back right one I seemed to hit solid clay. The soil changes colour again from an orange to a deep red. Hopefully this is a reasonable surface to pour concrete on - I know there can be issues with expansion after rain.

Image
This is the footprint of the foundation - I have reduced the size but think a slightly larger area than the brick pier should be fine considering this is just a deck. The concrete will range from 150mm to 700mm deep - I'm not planning on reinforcing it at all.

An unrelated point - I keep changing my mind about what sort of drainage is required for this type of building. I was going to do it the 'proper' way with underground pipe to a soakaway but think that may be a bit overkill.
Another option which I am warming to is just to run the overflow from the water butt under the deck to drain into the soil - I don't forsee any issues with this as long as it doesn't damage the foundations.

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Re: Workshop decking - Foundation piers query

Postby RogerS » 15 Jun 2021, 22:03

DomD wrote:
9fingers wrote:Hot work if you’ve been doing that today!

Yes, fortunately there is some shade up there but its 28C tomorrow when I'm panning on digging the rest of the holes :|

....

Dom


Please. Don't rub it in 'cos you'll get scant sympathy from these chilly parts. 9 degrees early morning.
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Re: Workshop decking - Foundation piers query

Postby DomD » 17 Jun 2021, 19:38

The temperature did thankfully drop a bit today and I finished off digging the holes and started to buy materials.

Image

The price of treated softwood seems to have skyrocketed at all suppliers (I knew there was a shortage but didn't realise it was so significant). Cement is also out of stock in lots of places but the DIY stores seem to have some and are limiting quantity per customer. Tomorrow I'm going to try and source all the aggregates and bricks.

For the joist-brick contact I think I will just use DPC. Any ideas on the best way to fix metal tie-downs to bricks? I could use some sort of chemical fixing with a threaded rod but maybe wall plugs and screws are enough.

Many thanks,
Dom
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Re: Workshop decking - Foundation piers query

Postby DomD » 23 Jun 2021, 20:47

Today I started to mix and pour the concrete:

Image

Image

Image

I'm using C20 (1:2:4, cement:sand:aggregate).
So far I've done 3/7 - mixing without a mixer is exhausting


I also got the first few joist hangers, these are the corner ones and are actually masonry hangers:
Image

I chose these as they won't stick out at the edges; the rest will be standard timber hangers. I'll need to cut a rebate in the wall plate for these ones so they sit flush with the top of the timber.

Hopefully will get some good weather over the next few days so I can finish the concrete and start at the brickwork.

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Re: Workshop decking - Foundation piers query

Postby NickM » 24 Jun 2021, 08:38

Looking good. I bought some unsorted redwood from Sydenhams last week and the delivery driver told me I'd done well to get hold of it.
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Re: Workshop decking - Attaching wall plate

Postby DomD » 28 Jun 2021, 13:16

I've now poured all the concrete and moved on to attaching the wall plates to the shed foundation,
Image

This timber is attached with throughbolts which I think are really meant for steel fixtures but seemed to work well here. I spaced the board off the concrete with galvanised penny washers to create a 10mm ventilation and drainage gap. The throughbolts are at 600mm centres and staggered diagonally.
Image

In some places, because the concrete foundation has bulged out under the shuttering, I had to chip away at the bulge with a masonry chisel to maintain a drainage gap.
Image

The wall plate is fixed so that with a 28mm decking board on top of it the surface will align with the bottom of the door.

I then attached one of the corner modified masonry hangers to check they would work as intended. I treated all the cut ends and rebate with wood preservative.
Image

The next job is building up the brick piers. I've read that ideally a deck has a bit of a slope on it so will have to ensure they finish slightly lower than the wall plate. It might be a bit of a challenge getting them all level as the concrete pads area all at different levels.

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Re: Workshop decking - Foundation piers query

Postby StevieB » 28 Jun 2021, 16:43

Looking good! The best way to do this I have found is to try and get them all level as early as possible, by using a cut brick as your first course if necessary. You can then build up from a level base. Trying to get them to finish level across the top will be near impossible. You can lose a tiny bit each course with thicker or thinner mortar where required, but getting the bottom course level will definitely make your life simpler and the piers neater.
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Re: Workshop decking - Foundation piers query

Postby Mike G » 28 Jun 2021, 17:38

Yep, Steve's absolutely right. Have it just about bang on by the top of the first brick.

My suggestion is to buy a few Flettons to use at the bottom, (first course). They are very easy to chip at with a trowel to reduce in height if necessary (and they're cheap :) ) Lay bricks frogs down if you need to get they're height down.

To others following along.........pour your pads level with each other, or to line with your chosen fall. ;)
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Re: Workshop decking

Postby DomD » 29 Jun 2021, 14:20

Ok that's what I'll try to do.

With a 1:100 fall I will try to get the piers at the front ~20mm below the wall plate base and the ones at the side 10mm below.

Getting some Flettons seems like a good idea as I am unable to break the Ibstock Heather bricks I got for the plinth cleanly. My only concern is the Flettons I've seen online all seem to be 'F1' which are not recommended for ground contact (the first course will be underground). Will this be an issue or is it fine?

Thanks for the help,
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Re: Workshop decking

Postby 9fingers » 29 Jun 2021, 14:49

In that case I'd suggest a few engineering bricks to get you out of the ground and then use your flettons.

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Re: Workshop decking

Postby Mike G » 29 Jun 2021, 15:51

Flettons are fine in the ground in this circumstance.
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Re: Workshop decking

Postby DomD » 03 Jul 2021, 12:35

Ok great - I won't be able to get much done in the next week as am off camping but hopefully should get to bricklaying after that.

I did get some guttering installed on the front:
Image
The downpipe will have a diverter in it for the water butt at the side.

I also finally removed the DPC covering the brick plinth and it looks really good - such a nice transition detail with the cove :)
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Re: Workshop decking

Postby DomD » 20 Jul 2021, 21:54

All the piers are now built up and ready to hold the timber frame. I'm planning to put down DPC and then just rest the joists on them. To hold the deck down during wind I think I'll run firband strapping down from the timbers to the concrete and screw it in place.

Image

The bricklaying isn't the best aesthetically and I did have to use thicker (~20mm) capping on some but it is perfectly level (20mm down from the front plate, 10mm down at the side). Most faces won't be visible anyway.

Image

The next job is getting weed fabric and bark down.
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Re: Workshop decking

Postby Mike G » 21 Jul 2021, 07:21

Well done Dom. Keep at it.
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