8ft block wall for shed storing compressed gass, best procedure

[JohnLeeWall]

Hi I am needing to build an 8ft high concrete block wall where a pent shed will be built from using a wooden frame and foam panels for light weight while the concrete wall is to stop damages encase of accidents while the light weight section will give. I am wanting to use standard concrete blocks. My footings are 1m deep as its clay soil to pure clay then hardened clay by 450mm wide with 12" concrete footing. The wall needs to go around 8ft tall but I know that will not work with a single skin. So I am wondering is it best to place the concrete blocks on their side so they are lay flat and will this stand fine at a single skin to 8ft tall? Or would it be best to do two skins side by side with block, no cavity, and tie these in periodically with wall ties or another idea is to do to blocks standard way up so 200mm thick then lay one flat on top then another flat then two standard until up to 8ft tall and would this hold fine? or would simply doing columns at either end on one side of the wall with the rest single skin hold fine? Building is 10x8.5ft in size. The interior will have a small wall coming away from the end to around 3 foot in and walled off again to the sides to create two small rooms which will store compressed gas and again will be a single skin wall with wood frame and plastered then tiled with an open roof to the wooden roof section.

The shed will connect by the wooden frame to this and the bottom will have 3 coarse of block , before the wood starts, to lift it away from the ground with these tying into the shielding wall at the rear. The roof will slope away from the rear wall down to the front.

 

[bernardgreen]

There are safety rules for the storage of gas.

Quoting from the HSE LINK

LPG cylinders
Cylinders should be stored preferably in the open air on a concrete or load-bearing surface. Flammable liquids, combustible, corrosive, oxidising materials, toxic materials or compressed gas cylinders should be kept separate from LPG containers in general. Containers should be stored with their valves uppermost. The maximum size of any stack should not exceed 30,000 kg. For storage indoors, no more than 5000 kg may be stored in each purpose designed building compartment and a maximum of five compartments may exist in a single building.

Storage in the open air in a wire mesh cage EXAMPLE allows any gas that leaks to dissipate. Storing cylinders in a shed without adequate ventilation could result in leaking gas building up to become an explosive mixture.

 

[JohnLeeWall]

(very long quotation) .

The shed will be ventilated and is designed to give encase of explosion though the wall needed is to help negate a blast travelling in the way of other sheds so that it goes in the direction of least resistance ie upward and outward to one side. Usually the older buildings contained a two compartment building divided with a dual skinned brick wall but these are very old and not of great service so is the need for the newer structure out of more modern block material though the height being a concern in terms of building the single wall. The shed though will be adequately vented.

 

[^woody^]

Two skins or one block flat will be the same for strength. Whether a single skin will do will need someone to calculate. A single skin with piers will certainly be OK for a shed wall.

 

[JohnLeeWall]

Two skins or one block flat will be the same for strength. Whether a single skin will do will need someone to calculate. A single skin with piers will certainly be OK for a shed wall.

In terms of stability at 8ft tall would laying blocks flat be safer than upright or dual upright blocks then two flats then upright and so on? or just upright with a column either end and one in middle on backend of wall?

 

[^woody^]

Garages are built of single block skin. You would design additional wall support via roof bracing.

 

[JohnLeeWall]

Attached image of shed design, My main worry is because this has no side walls in block like say a garage does it will be weaker even with wood framing attached due to its weight in stability. Going off the design the first 3 courses above dpc will be block then the rest is wood frame with light weight padded paneling. The block wall at the rear is 8ft tall and in that image single skinned only.

Shed Design

• JohnLeeWall
• 10 Jun 2021

 

[bernardgreen]

LPG is heavier than air so that it will settle and may accumulate in low spots such drains and basements. Here it could present a fire or explosion or suffocation hazard.

Hence to dissipate leaking gas you will need ventilation at floor level and then space outside for the gas to disperse

 

[^woody^]

Any four-sided structure with a roof is inherently strong due to the shared bracing and support, and it does not matter is made of timber or wood.

What you are trying to do and being fixated on is trying to design something that deals with a potential blast in a known and controlled way and to do that it must be designed by someone who is qualified to do that. If you don't know how the pressure from a blast radiates then you don't know how an ad-hoc shed is going to perform.

Just by looking at it, it would seem to me that any blast may wall blow the window, roof corners of the timber panels and whether that then topples the wall, who knows. And all this may well occur in micro-seconds all at once.

If this is a business location, in any incident the issue would be what have you done to provide a a safe storage shed and what risk assessment have you done. And "suitable" design may well be paramount, and suitability would need to be determined by an expert. And if you are doing this as a job, then you must be qualified to do it, otherwise it's basic negligence.

 

[bernardgreen]

You need to take the advice that Woody has given you

You need expert advice, specifically on the possibility of multiple blasts. The first "explosion" can be a mild one as an accumulation of leaked gas ignites. It may do little damage to the building and may go un-noticed. The leak continues with the leaking gas burning as it comes out of the leaking cylinder. The heat from this flame may cause other cylinders to over heat and explode. ( google bleve to see how serious this type of explosion can be. )

 

[^woody^]

IIRC, the storage of bottled gas on site only requires a secure area in a suitable location and this is normally just a cage or a sheet metal surround of some sort. So no protection from blasts.

Is this a different scenario?

 

[bernardgreen]

So no protection from blasts.

The open air storage prevents build up of enough gas to cause an explosion if ignited. And in open space it tends to be be very rapid burning. Only when the gas is in a confined space can it's rapid burning and resultant expansion by heating cause the air / gas pressure to increase. The pressure may increase to the point where it breaks the containment ( building ) and this sudden release of pressure is the "blast".

 

[JohnLeeWall]

The gas being stored is not lpg but a by product gas from a production and is more vapor in effect but when confined turns more gaseous. So the vapor is not explosive but when compressed it can act that way but rarely. Our old building used a 8ft tall dual skinned brick wall with coarse interlocking between each other every so often. The rest was shed and board. We only need the direction of a blast to go mainly in one direction outside of this is also a steel caged wall at a defined separation distance. We have all the safety assessments for the building and defined distances and heights and the block wall is classed as adequate enough for the small amount stored and building size given the expansion ratio before it even catches the walls. Like I say its more precautionary and wont burn up like say lpg does, methane or other forms of gas. More main worry was the stability of a block wall staying upright in general as building regulations seem to state not to do a single skin above 6ft I believe if unsupported and the brick far outweighs the wood beams. Its that time frame where it is stud up before the wood sections are built. This is why I was thinking dual skin or lay belly flat.

 

[bernardgreen]

So the vapor is not explosive but when compressed it can act that way

A gas refers to a substance that has a single defined thermodynamic state at room temperature whereas a vapor refers to a substance that is a mixture of two phases at room temperature, namely gaseous and liquid phase. A vapour can co-exist with a liquid or solid when they are in equilibrium state.

a by product gas from a production

That implies a commercial or industrial application is involved and hence you should be seeking and following the advice / regulations from the Health and Safety Executive

 

[JohnLeeWall]

A gas refers to a substance that has a single defined thermodynamic state at room temperature whereas a vapor refers to a substance that is a mixture of two phases at room temperature, namely gaseous and liquid phase. A vapour can co-exist with a liquid or solid when they are in equilibrium state.



That implies a commercial or industrial application is involved and hence you should be seeking and following the advice / regulations from the Health and Safety Executive

That we have already and they give the guidelines and safety measures to put in place and we need the concrete block or concrete poured wall but preferably block as it would work out better. So the design we have gone with suits these requirements that we have to follow including separation distances. My only concern like I say is the height of a concrete block wall would it be stable enough in just normal use standing going off of the ideas in my original post. Obviously with say a garage the side walls are tied into the long walls so its a cube and that gives the strength. In my case we dont have this. There will be a short gap to wall being erected before wooden frames are put in place. As for thickness anything from 100mm to 400mm is fine for us to use as its a precaution measure rather than say a full on shield like in military or pyro applications and the block wall will be quicker to erect than a dual skinned brick wall for us.