Thread: My shed, about time

KJ.

I imagine you will require more than a single leaf of 110 brickwork to retain the soil. At the least it would be double brick with a 600 wide by 250 deep reinforced ( trenchmesh) concrete footing. My shed floor is 100 mm thick. I think the mesh I used was F62 ( 6mm rod on a 200mm square grid ). People will tell you to make it thinner. Depends what you plan putting on it. Consider some form of termiticide, if termites are a problem, on the compacted soil prior to the laying of the concrete. Also, to ensure alignment between the two slabs, drill and chemical anchor 12mm steel bars at maybe 400 centres, in the edge of the existing slab. Before you backfill against the new brick retaining walls, apply a waterproof barrier coating to the brickwork. You may need to consider some sort of drainage system at the base of the wall. Something like perforated pipe with a gravel cover.

I will discuss the above with one of the blokes at work who is better versed at this sort of stuff than I am. I will confirm the wall and footing details and wire you a sketch.

Do you need to replicate the existing post and beam design? Be cheaper not to. How to you deal with roof drainage?

I know nothing about blue wall. Is it the fibre cement sheet that is render finished? Think about insulation. I didn't and rust is a constant problem.

Draw elevations and sections.

BT

Ken

It may be wise to overexcavate between a metre to 500mm along the house side and along the back wall of the extension and build a seperate retaining wall/drainage channel. This will reduce the difficulty of dealing with drainage/condensation issues on the shed extension walls. It will also allow you to construct external stairs down to your side door (which I would put at the back corner).

Mav

There is merit in Mav's suggestion. Things would become simplified. The retaining wall could be limestone. No footings required so overall it could be a cheaper ( and quicker ) option. The shed walls could run down past the concrete slab edge thereby excluding water. Do you have the room for additional excavation Ken?

BT

I used to live on Hawdon St!

Originally Posted by Anorak Bob

. . . The shed walls could run down past the concrete slab edge thereby excluding water. . . .

That's how I have mine constructed. It definitely reduces the number of headaches with water sealing around the slab

Excavations and retaining walls; all it brings to mind for me is damp and possibly wet conditions.

If at all possible I would be trying to get the extension above the level of the existing garage, even putting stairs from the garage to the addition. Sure it will cost a little more, as no doubt a concrete pump would be required, however that will be more than offset by the cost of the reinforced retaining wall, waterproofing said wall, and the drainage system required. On top of that, you could possibly build a bigger space if able to and required.

JMHO for what its worth.

Originally Posted by wun4us

Excavations and retaining walls; all it brings to mind for me is damp and possibly wet conditions.

If at all possible I would be trying to get the extension above the level of the existing garage, even putting stairs from the garage to the addition. Sure it will cost a little more, as no doubt a concrete pump would be required, however that will be more than offset by the cost of the reinforced retaining wall, waterproofing said wall, and the drainage system required. On top of that, you could possibly build a bigger space if able to and required.

JMHO for what its worth.

And given that the shed has street frontage, the council will enter the fray. Maybe Ken 's interest in all this has waned and he returned to the idea of using his neighbour's carport to store all his shyte.

Or build it behind the house. I had my new shed built up the end of the yard about 20m, no vehicler access, the concretor knew this and arranged his work crew to handle this. It cost me a little more, less than getting a pumper in.

Gentlemen,

Thank you for all your comments. I'm pretty well convinced to build my shed as an adjunct to the existing garage. The benefits are lower cost, only require two walls and a roof, side boundary fence serves as one wall, and, close to the street for delivering material. Being a one car family, half the existing garage will be incorporated with the extension, more floor space.

I have attempted to knock up a section drawing, not finished, and ask for details re the water proof barrier under the slab. Thickness and correct description etc.

I still reckon a one piece slab to be the best option, thickened up under the brick columns, and around the perimeter, if required.

AB, your wisdom re starter bars wacked into the end of the existing slab, is a good idea.

What grade of sawn oregon is specified these days, I haven't been involved in the building industry for many, many, years.

Just thought of another question, I will be using Lysaught klip-loc 406 roof decking, is there a transparent sky light sheet that matches the same profile?

Attached is a partly finished cross section. I apologise for the poor image quality, all lost in the translation from Autocad to pdf to jpeg.

Ken

Ken,

Do the brick columns actually need to be square? Simple brick angles (in plan) would suffice and not be intrusive, space wise, inside the shed. Externally, they would read as columns.

Check the Laserlite website for roofing profiles. I think you will be out of luck trying to match Kliplok. Keep in mind the minimum roof pitch required for plastic roof sheeting.

Laserlite | Bayer MaterialScience - Sheeting Products

Over here, treated structural pine is the norm for roof framing. You need to have a look at span tables to size your purlins.

I'm not up with clay foundations but 50mm of sand seems thin.

BT

BT,

The brick columns need not be as drawn, and as you suggest, just fabricating something up that resembles a corner, is all that's required. All I need is the look of the existing columns. I could knock up an L-shaped timber frame, and clad it with Blue Board. Rendered, you would never know the difference. And as you say, I regain floor space for say a bench etc up to the corner.

Using this type of construction, may negate the need to thicken up the slab in the corners.

Anyone know how thick the sand should be under the slab? 100mm? Still waiting on answers to some questions above. Any further takers?

Laserlite don't seem to have a product that will match the Lysaught roof decking profile. Surely someone makes a product that will blend in?

If no, I'll wack a window in the West end wall, up high.

Ken

KJ,

Since the roof looks like it can't be seen, could you use Trimdek, a profile also available in translucent sheeting? How is the original roof drained? Remember, you need insulation under the sheeting.

BT

Hi BT.

Correct, the roof will not be seen, will check out Trimdeck.

The original roof is drained exactly as the cross section of the extension indicates. A custom gutter runs down from the West end to the street end, and terminates with a rectangular downpipe.

The downpipe drops down next to the front column, then disappears into a storm water pipe to re-emerge into the gutter under the footpath.

Edit,

Looked at the Lysaght Trimdeck, nah, doesn't look very strong to me.

Ken

With 100mm slab you need min 50mm sand. With no footing you need an edge thickening around the perimeter (200w x 100thicker than the rest of the slab). If you're putting in a heavy mill or lathe I'd also thicken up the slab below where its going. No matter what you decide for corners you will need tiedown to the roof. From Bunnings for each corner get 2 off M12 angle starters, 2 off extenda nuts and 2 off M12 tie down rods (available in 2.4 to 3.0metre lengths) tie them to an angle bolted to your perimeter beams , one to the side beam one to the back beam.(a very cheap way of buying M12 all thread). Set the angle starters in the concrete as soon as its poured (while still wet) with the nuts attached and the top of the nuts taped.

If you go for brick piers they will need at least a 300 - 450 deep footing with a bit of trench mesh for reo.

Kliplock is normally used in marine type environment - no need to penetrate the sheeting causing corrosion because of the method of fixing. But very expensive compared to other sheeting. Unless you are close to the coast Trimdeck would be more than adequate but you would have to flash over the join.( Would also give you the ability to put clear sheets in for light).

I used to be a builder but now I work for the Council ....... Where did you say you lived?



Mav