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EPISODE: 025 - APPROVED DOCUMENT J - COMBUSTION APPLIANCES AND FUEL STORAGE SYSTEMS

Updated: Jun 23

BYTNAR - TALKS

EPISODE 025 - APPROVED DOCUMENT J - COMBUSTION APPLIANCES AND FUEL STORAGE SYSTEMS


This episode is for people who want to know more about Approved Document Part J – Combustion Appliances and Fuel Storage Systems.


You should like this episode if you ask yourself questions like:

  • What are the key requirements for installing combustion appliances and fuel storage systems in domestic buildings?

  • What standards and guides, such as CIBSE Guide B and BSI, are referenced in Approved Document J for combustion safety?

  • What are the general safety provisions for the installation of combustion appliances, including air supply, ventilation, and flue systems?

  • How should carbon monoxide alarms be installed to ensure safety according to Approved Document J?

  • What specific requirements must be followed for installing solid fuel appliances up to 50kW output, including air supply and flue specifications?

  • What are the safety guidelines for installing gas appliances, and why must a Gas Safety registered professional handle the installation?

  • What are the ventilation and flue requirements for gas appliances in sleeping or bathing areas as mentioned in Approved Document J?

  • What special considerations are needed when installing oil-burning appliances, particularly in relation to flue gas temperatures and materials?

  • How should oil and LPG storage be managed to prevent fire risks and environmental damage, and what are the guidelines for secondary containment and fire-resistant barriers?





This is Bytnar Talks: The Engineer Takes on Construction, Episode 25

Hi, I'm Piotr Bytnar. Each day, I help my clients plan and design building projects through Bytnar Limited, a consulting Chartered Structural Engineers practice.

My biggest passion — and the cornerstone on which I've built my business — is finding clever solutions for construction projects. I am a chartered structural engineer and a budding software developer, so you can rest assured that I will strive to talk about the best practices and the use of new technologies in the industry.

And if you're embarking on a construction project or are involved in planning, designing, and building the world around us — you'll find this podcast useful.

Approved Document J — Combustion Appliances and Fuel Storage Systems

Hi, and welcome back to Bytnar Talks, your favorite podcast on all matters of architecture, engineering, and construction.

It is Thursday, the 5th of August 2024, and I'm here back with you for the 25th episode, with information on Approved Document J: Combustion Appliances and Fuel Storage Systems.

We are at the eve of summer holidays — believe it or not, these episodes are not curated by an army of employees powered by AI. So the host — meaning I — needed a little break.

I now return to you from the scorching coast of Italy, back to the southeast of England — a country where we can afford outside air conditioning... oh sorry, it's just the weather that’s not as nice as our flour-, tomato sauce-, and cheese-loving friends is.

However, before I get to covering the material of this episode, let's have a look at what was covered last week.

In the last episode, I talked about Approved Document H: Drainage and Waste Disposal. There are six requirements covered in that document:

  1. Requirement H1 — Foul Water Drainage


    Focuses on ensuring proper capacity, minimizing blockages and leaks, providing access for maintenance, and preventing foul air ingress or backflow into the property.

  2. Requirement H2 — Wastewater Treatment Systems and Cesspools


    Tells us that systems must avoid nuisances, health hazards, and pollution, with adequate ventilation and access for maintenance, as well as adherence to Environment Agency guidelines and BS standards.

  3. Requirement H3 — Rainwater Drainage


    Explains that systems should effectively carry water from roofs and paved areas, prioritizing soakaways first, then watercourses, with discharge to sewers as a last resort.


    We must consider correct sizing based on tributary area and local rainfall, and ensure accessible maintenance points are included in the system.

  4. Requirement H4 — Building Over Sewers


    Ensures that new buildings do not affect existing drainage systems, obstruct maintenance or replacement, or compromise building stability due to drainage issues.


    We are reminded in that section that an agreement with the drainage system owner is required.

  5. Requirement H5 — Separate Systems of Drainage


    Instructs that separate systems for surface and foul water are necessary — ideally directing surface water to soakaways or watercourses.


    If a combined system is required, it must be used properly and agreed upon with the local authority.

  6. Requirement H6 — Solid Waste Storage


    Focuses on providing adequate, accessible, and vermin-proof waste storage facilities to prevent health hazards and maintain hygiene — ensuring ventilation and weather resistance.

In this episode, I will move to Approved Document J — Combustion Appliances and Fuel Storage Systems.

So without further ado, let's dive straight into it.

In this episode, I'll talk about the statutory guidance contained within Approved Document J: Combustion Appliances and Fuel Storage Systems. The episode will follow its standard format for the material, talking about the Approved Documents:I will first read you the text of the actual regulation, and then we’ll go section by section.

The document contains guidance for the discharge of Requirements J1 to J7, across six sections (numbered 0 to 5), with additional information in appendices.

So, let’s get into the nitty gritty of this Approved Document.

Starting with the text of the legislation:

Part J — Combustion Appliances and Fuel Storage Systems

Air Supply – J1Combustion appliances shall be so installed that there is an adequate supply of air to them for combustion, to prevent overheating, and for the efficient working of any flue.

Discharge of products of combustion-J2

Combustion appliances shall have adequate provision for the discharge of products of combustion to the outside air.

Now, Requirements J1 and J2 apply only to fixed combustion appliances, including incinerators.

Warning of Release of Carbon Monoxide — Requirement J3

Where a combustion appliance is provided, appropriate provision, having regard to the design and location of the appliance, shall be made to detect and give early warning of the release of carbon monoxide at levels harmful to persons.

Requirement J3 applies only to fixed combustion appliances located in dwellings.

Protection of Building — Requirement J4

Combustion appliances and flue pipes shall be so installed, and fireplaces and chimneys shall be so constructed and installed, as to reduce to a reasonable level the risk of people suffering burns or the building catching fire in consequence of their use.

Requirement J4 applies only to fixed combustion appliances, including incinerators.

Provision of Information — Requirement J5

Where a hearth, fireplace, flue, or chimney is provided or extended, a durable notice containing information on the performance capabilities of the hearth, fireplace, flue, or chimney shall be affixed in a suitable place in the building, for the purpose of enabling combustion appliances to be safely installed.

Protection of Liquid Fuel Storage Systems — Requirement J6

Liquid fuel storage systems and the pipes connecting them to combustion appliances shall be:

  • Constructed and separated from buildings and the boundary of the premises in such a way as to reduce to a reasonable level the risk of fuel ignition in the event of a fire in adjacent buildings or premises.

Requirement J6 applies only to:

  • Fixed oil storage tanks with capacities greater than 90 L, and connecting pipes; and

  • Fixed liquefied petroleum gas (LPG) storage installations with capacities greater than 150 L, and connecting pipes which are located outside the building and serve fixed combustion appliances, including incinerators, in the building.

Protection Against Pollution — Requirement J7

Oil storage tanks and the pipes connecting them to combustion appliances shall:

  • Be constructed and protected in such a way as to reduce to a reasonable level the risk of oil escaping and causing pollution, and

  • Have affixed, in a prominent position, a durable notice containing information on how to respond to an oil escape, so as to reduce the risk of pollution.

Requirement J7 applies only to:

  • Fixed oil storage tanks with capacities of 3,500 Lor less, and

  • Connecting pipes which are:

    • A. Located outside the building, and

    • B. Serve fixed combustion appliances, including incinerators, in a building used wholly or mainly as a private dwelling.

This does not apply to buried systems.

Easy peasy, lemon squeezy, straightforward stuff, isn’t it?

On this occasion, as in many other requirements, we find expectations that fall outside of the merit of just providing reasonable protection to the health and safety of people in and around buildings.

This is placed on us in Regulation 8. In this case, it is Part J7, as it deals with protection against pollution.

It needs to be noted that the requirement is enforceable only on particular types of building work or material change of use, and some building classes may be exempt from the regulations.You can find the list of classes in Schedule 2 of the Building Regulations.

Having said that, Building Regulations do not stand alone.

For example, gas installations fall under the Gas Safety (Installation and Use) Regulations 1998.

Further requirements may come from:

  • The Workplace (Health, Safety and Welfare) Regulations 1992, or

  • The Clean Air Act 1993, as amended by the Environment Act 2021.

Schedule 4 of the Building Regulations lists the number of works that do not need to be notified to Building Control.

But work on combustion appliances, unless it is purely repair or maintenance, will need to be notified to Building Control

In case anyone is wondering, the standard of the work and use of materials must be right and proper, as must the periodical maintenance and service.

Before you start dreaming of owning an open fireplace, do check if you live in a smoke control area.In such areas, you may be required not to use any appliance, or only to use an authorised type of fuel, or an exempt appliance.

Starting with Section 0

It needs to be understood that the Approved document’s guidance has been prepared mainly with domestic installations in mind and covers combustion appliances and their fuel storage systems, including solid fuels — things like space and water heating units, and cookers.

The installations covered in the guidance are:

  • Solid fuel installations of up to 45 kW of rated output,

  • Gas installations of up to 70 kilowatts of net, or 77.7 kilowatts of gross rated input,

  • Oil installations of up to 45 kW rated heat input/output,

  • And fuel storage of up to 3,500 litres of oil or 1.1 tonnes of LPG.

Guidance outside of these parameters can be found in:

  • Chartered Institution of Building Services Engineers (CIBSE) Guide B,

  • Materials produced by the British Standards Institution (BSI),

  • And the Institution of Gas Engineers and Managers (IGEM).

The guidance goes on to address considerations for different appliances used in different ways. It breaks this down by fuel type: solid, oil, or gas.

Air Supply:

  • Open flue systems may draw air through background or dedicated inlets to the room;

  • Room-sealed systems take air directly into the combustion chamber through a flue.

In any case — whether open or room-sealed — combustion can also be assisted by fans.

Combustion Products Removal:

  • This may happen by natural draught, flue fan, or, in some cases, be flueless.

  • The draught may also be mechanically assisted, diverted, or stabilised using components like draught stabilisers or breaks.

This section goes on to describe all the different elements that may form part of the installation or affect the installation of combustion appliances — including fireplaces, structural recesses, their shape and lining, and whether or not they are suitable for different fuel types.

I really like this document — it’s full of descriptions and diagrams, making it very easy to follow. Like:

  • Diagram 6, showing a cross-section through the floor containing a hearth, or

  • Diagram 7, which makes absolutely sure — really, really sure — that you know taking a diagonal measurement through the flue is not the correct way of doing it.

Section 1

Section 1 starts by telling us that the Secretary of State is satisfied if:

  • The installation is good and proper in terms of specification, materials, size, workmanship, and inspection;

  • Carbon monoxide alarms are provided for solid and gas appliances (excluding cookers and oil appliances);

  • And any fuel storage (oil or gas) is properly installed, with the performance capability of the system clearly labelled.

Air supply and flue size will depend on:

  • The type of appliance,

  • The required air intake,

  • The number of appliances,

  • And any cooling requirements.

All of this is nicely illustrated within the diagrams in the document.

Permanent open vents:

  • Must be properly sized,

  • Take into consideration any grilles or mesh (with no less than 5 mm gaps),

  • And must be located so the occupiers cannot seal them.

They should also ensure that:

  • Draughts do not become a nuisance,

  • And that they do not disturb the combustion process (e.g. blowing ashes or pulling flames forward).

The location of air vents will depend on the performance and placement of the appliance.

Care should be taken when working with protective membranes — such as:

  • Breather membranes,

  • Vapour control layers in timber frame construction, or

  • Gas barriers below ground.

The Approved Document provides typical suggested vent locations.

We may be able to count these openings toward background ventilation for the purposes of Requirement F, but not the other way around, due to the simple fact that combustion ventilation must remain constantly open.

Purge ventilation will also be necessary in such instances.

We also need to ensure that, if rooms are mechanically ventilated, there is not excessive depressurisation.

That’s the tough one — depressurisation — which could back-route the combustion products, creating a reverse suction effect in the flue and potentially filling the room with combustion gases. We do not want that.

The guidance gives limits for fan extraction maximums in rooms with different appliances:

  • For gas appliances: 20 L/s,

  • For oil appliances:

    • 40 L/s for pressure jet burners,

    • 20 L/s for vaporising burners,

  • For solid fuel appliances: 0 L/s — unless it can be proven that the installation remains safe in operation.

Similarly, for commercial installations, extra considerations may be required to ensure:

  • Proper air supply,

  • Correct flue design,

  • And adequate combustion product circulation.

Extra care is also advised where ground gases are being ventilated away from underneath the building, to avoid recirculation back into the property.

The guidance directs us to the now-withdrawn Building Research Establishment Good Building Guide 25, which deals with radon, and shows us the particulars of the sort of circumstances. Check and assure no backdraught or harmful gas spillage is needed — I will until running the walls the pressurization… well, the depressurisation — that’s a tough one. My leg—my tongue isn’t capable of doing that one properly — of the room scenario, using all fan systems and different arrangements of open or closed windows and doors.

The spillage test may come from proprietary literature, or British Standards, or other publications like those produced by the Oil Firing Technical Association.

Unless the system is flueless, we will need to provide a flue or chimney — separate for each solid-fuel burning appliance, but can be combined for other fuels.

However, the guidance only covers single flue or chimney systems and references:

  • BS 5410 for oil, and

  • BS 5440 for gas installations.

The chimney should not be prone to condensation, so for non-condensing appliances it’s best if the flues are insulated to avoid this during normal operation — or otherwise, be made of materials appropriate to resist corrosion and allow for drainage of condensate.

Masonry chimneys should be:

  • Sufficiently strong,

  • Thick, and

  • Of sufficiently dense material,

with the flue lined using a liner at least as good as designation T400 N2 D3 G, to BS EN 1443 standard.

This can also be a clay flue liner or concrete liner.There’s no single right answer here — use what is compatible with your system and meets the standards.

Typically, you’ll be using proprietary products, so follow the manufacturer’s instructions.

Naturally, just to mention the obvious: the elements should be joined up correctly using a route of high temperature–resistant, also called fire or refractory cement.

The space between the flue lining and the masonry should be filled with a lightly wetted lean mix of cement, comprising:

  • One part cement, and either:

    • 20 parts lightweight expanded clay aggregate, or

    • 6 parts vermiculite, or

    • 10 parts perlite (just for installation purposes).

An alternative to using liners is to use a proprietary flue block system of sufficient designation and durability, installed to the manufacturer’s specification.

Adapting existing chimneys or flues should be done with due consideration to:

  • Their current state,

  • Condition of repair,

  • Connection type and materials, and

  • Insulation from other building elements.

Flues are controlled services, and the introduction of a new flue liner or replacement of an existing one will require notification to Building Control.

Metal liners should be replaced together with the appliance, and a flexible liner cannot be used as a primary liner.

You can use plastic flue pipes that conform to BS EN 14471, appropriate for the appliance type and fuel.

When it comes to factory-made metal chimneys, they need to follow standards applicable to the fuel type being used.

Perforation of walls and floor plates, as well as heat-related detailing of the installation, should be carefully considered — such as safe distances from the flue, as described in BS EN 1856.

The joints of these flues need to be serviceable.Any concealed flue must be accessible for inspection, with access hatches of at least 300 mm², not farther than 1.5 m from the joint or a bend.

Natural draught flues, serving open-flued appliances, should be ideally vertical, with no bends, discounting the outlet from the appliance — which itself should be no more than 150 mm from the appliance.

A maximum of four bends of maximum 45° is allowed, with a 90° proprietary appliance outlet counting as two of those bends.

Access for inspection and sweeping should be provided for every two bends.

We are reminded that low-level outlets may be disrupted in future due to neighbourly extensions — but dread not, as the guidance comes with a diagram showing the appropriate locations.How would it do it otherwise, right? These documents are brilliant.

We are also informed to avoid creating voids near combustion appliances to which gases could escape — things like decorative dry-lining surrounds, which should have such gaps well sealed.

The responsibility to discharge Requirement J lies with the person executing the works.

Reports stating the elements of the installation are suggested in Appendix A of the document, and tests, per the guidance of Appendix E, should be collected and ready for submission to Building Control.

The installation should be:

  • Free from obstruction,

  • Gas-tight,

  • Of proper materials and workmanship,

  • Spillage-tested during commissioning, and for Part L compliance,

  • Hearths should be of the right size and material.

The information about hearths, fireplaces, flues, and chimneys needs to be permanently posted in the building to avoid misuse. So, information on their location, size, category, make, suitability, and installation date — an example of such a notice is provided within the document. The position of this plate should be such that it is readily accessible, so places like near the consumer unit, next to the stopcock, or adjacent to the actual chimney will do just fine.

Roof space–installed gas-fired appliances should follow the (now withdrawn) BS 6798, Specification for installation and maintenance of gas-fired boilers of rated input not exceeding 70 kW net.

Now, we move to Section Two, which extends the information provided in Section One, concentrating on appliances burning solid fuel, including biofuel, with a rated output up to 50 kW.

Air Supply

Air supply to these beasts needs to follow minimum requirements, but may require more, depending on the type of appliance and the type of fuel used. Checking the manufacturer’s specifications or the tables in the approved document would be the starting point for consideration.

For example, an open fireplace under a canopy or with a throat requires a fresh air supply of at least half of the exhaust capacity — meaning half the size of the flue.

In the case of the canopy overhead, it will not be a surprise, but the flue also needs to be of appropriate size and run, starting at the size of the appliance outlet, or it can be looked up in the document’s tables.

So for example:

  • Fireplaces start at 200 mm diameter size or equivalent,

  • For closed appliances, we start smaller — from 125 mm diameter flue.

Large opening fireplaces should have a flue of at least 15% of the total face area. However, should the size be larger than 0.12 m² or exceed the 15% limit, we are encouraged to seek specialist advice.

Flue Height

We are guided in the subject of flue height, which should be high enough to develop sufficient draught.The figure will depend on:

  • The type of appliance,

  • Number of bends, and

  • Local wind patterns,

but we start at 4.5 m high.

We can calculate the actual requirement using the procedure in BS EN 13384, a standard that deals with thermal and fluid dynamic calculation methods for chimneys.

The height is measured either from the appliance outlet, or the point where exhaust gases enter the chimney.

The flue outlet position should also be considered — we cannot just plonk it anywhere on the roof. It needs to be positioned so the exhaust gases can freely disperse in the air.

The document provides a handy diagram, but the gist is simple:

There are three distances to consider:

  • 600 mm,

  • 1,000 mm, and

  • 2.3 m.

2.3 m is a horizontal distance to any:

  • Other roof feature or protrusion,

  • Other buildings, or

  • Windows.

In most cases, the outlet should be at least 1 m in height, but will likely need to be either:

  • As high as the ridge,

  • 600 mm higher than the ridge or adjacent feature (if close to them), or

  • At least 1 m above any opening.

This is for typical roofs.

If the roof is made of readily ignitable material, the outlet needs to stand at least 1.8 m tall generally, but at least 600 mm above the ridge level, for any distance up to 2.3 m away from the ridge.

Thatched roofs attract further consideration, especially regarding temperature insulation between flue and thatch.

Connecting Flue Pipes

Connecting flue pipes are just that — connections between the appliance and the chimney.They should be:

  • Proper, and

  • Not hidden within buildups.

The distance between them and combustible materials should be at least three times their diameter.

If they need to be closer, the distance can be reduced to 1.5 times the diameter, provided a non-combustible shield is installed to a distance at least 1.5 times the diameter in all directions.

The document requires at least 12 mm air gap between the combustible material and the shield.

The flue should be serviceable and have an accessible debris collection feature.

Masonry chimneys should be at least:

  • 100 mm thick in general,

  • 200 mm where between other properties or fire compartments.

Combustible materials should be:

  • At least 200 mm away from the inside of the flue or recess, or

  • 40 mm from the face of a masonry chimney or fireplace,

unless it’s a wall or floor finish like a skirting board or a mantelpiece.

Metal fixings, however, can be as close as 50 mm to the inside of the flue liner.

It’s all about heat dispersion through materials, and what effect it may have on combustible materials.

The guidance also tells us that open fire pits should have gathers that lead smoke into the flue at an angle no less than 45°, and that the hearth should be of appropriate size and material selection, of which will depend on the heat dispersion of the appliance. For example, appliances that do not give away more than 100°C from below it may be, the hearth requirement may be as little as 12 mm thick tiling. But for structural hearths, we talk of a minimum starting at 125 mm. Diagrams contained in the document nicely convey all the geometrical constraints for all different types of appliances—from open fires to low-heat output.

It is important to monitor air quality in the room containing an appliance that burns fuel, and the way to do it is by a carbon monoxide alarm, in line with BS EN 50291—either battery- or mains-powered—located 1 to 3 m away from the appliance, on the ceiling 300 mm away from walls, or on the wall at least 150 mm away from the ceiling, path over doors and window openings.

When the hearth and appliance are placed close to the wall—within 50 mm—the wall needs to be at least 200 mm thick and be at least 1.2 m above the hearth and at least 300 mm above the appliance. When the appliance is further away but not further than 300 mm, the thickness of the wall goes down to 75 mm. When the hearth detaches from the wall up to 150 mm, we need to provide a minimum thickness of the wall of 75 mm. But further away, there is no such equirement anymore.

I do strongly suggest you guys have a look at the diagrams within the document—these are very, very good and clear.

Now, Section Three expands on the provisions of Section One, considering gas-burning appliances with a rated input of up to 70 kilowatts net. I could simply say: do not worry, just get an appropriately competent installer registered on the Gas Safe Register—firm or person—involved and let them do the magic, as undoubtedly that is what the Approved Document asks you to do when it comes to gas installations.

The Gas Safety (Installation and Use) Regulations is the piece of legislation that fully covers the subject. In general, appliances fitted in the room where people sleep or bathe should be of room-sealed type.

There are numerous different gas appliances, including cookers, room heaters, decorative fuel effect fires, instant light fuel effect fires—and each will come with their requirement for air supply and/or change of the air in the room when the products of combustion are released into the room.

The basic limits for the minimum provision of open air vents will depend on the type of appliance—whether open-flued or room-sealed, free-standing or enclosed within a compartment within the room—and then the compartment being either ventilated through the room or to the outside air.

Similarly, for the consideration of flueless gas appliances, there are limits given within the document—going by the type of the appliance, each heat input, the volume of the room, and the free area of permanently open vents.

The size of the flue follows similar considerations of Section Two. So for gas appliances imitating fireplaces, the flue diameter will start at 175 mm, and for radiant or convector gas fires at 125 mm. The height of the flue these days usually follows the manufacturer's specifications. For older installations, we may need to go back to old standards, or we may need to calculate it.

The location of the outlet for the combustion gases is not as stringent as the one for solid fuel burners. Nevertheless, we want to minimize the impact of a gas plume leaving our building. There are too many places where we can place the outlet on our building to tell you all here—they do take two pages of A4, one for the text and the other a diagram—so do check it out for further information.

The distances are generally somewhere between 300 mm to 2 m. For a roof situation, close to the boundary or the roof window the penetration of the outlet should be at least 600 mm to the sides and top of the opening, and 2 m under. The guidance provides a warning that the locations of the condensing boiler outlets, even though defined under Building Regulations, may be a nuisance to our neighbors under the Environmental Protection Act, and should perhaps be as far as directed in the guide. And we should search for further guidance in the Guide to Condensing Boiler Installation Assessment Procedure for Dwellings.

Naturally, the flue outlets need to be protected from blockages and tampering, properly selected and installed. The requirement for the provision of a carbon monoxide alarm follows from Section Two.

Now off to Section Four, which deals with additional provisions for Oil-burning appliances with a rated output up to 45 kW are considered. It considers appliances that burn kerosene and gas oil (Class C2 and D to BS 2869), or liquid biofuel to EN 14213, or blends of fuel. The provisions for location, ventilation, and outlet location follow those for gas appliances—albeit ever so slightly differently—so do not assume they're the same. Go and check the tables and diagrams in the document.

The Secretary of State, in this Approved Document, is concerned about the temperature of gases traveling within the flue. Most appliances should produce exhaust gases well below 100°C, but we are advised to check the manufacturer's literature. In doubt, or lacking information, we should think of gas temperatures in excess of 250°C.

In line with the need, the chimney should be lined with materials of appropriate designation. Similarly to other sections, hearths and provisions for gathering oil spills should be made as necessary—as is the provision of carbon monoxide alarms.

Section Five deals with provisions for liquid fuel storage and supply. In this, the oil and LPG units and their installation should be so located and constructed to avoid their damage—especially during a building fire or a fire close to the boundary—and be labeled with information on how to deal with leaks.

There are certain limits on the size of installations that this document covers, and these are different for the protection of the storage and for environmental concerns—especially where the tank serves more than one dwelling. If in doubt, the Fire Authority can be consulted, and the Control of Pollution (Oil Storage) Regulations 2001 may need to be read.

The protection of oil tanks will consist of a solid concrete base to start with. Then, we can either enclose it with a special fire-hazard room, or—if it is closer to the building than 1.8 m—we should either make the building imperforate to fire for at least 30 minutes, or provide a barrier. Either way, such constructed shields—free-standing or as part of a building—should extend 300 mm beyond any side of the tank.

If the tank is less than 760 mm from the boundary, we will need to construct a wall of 30 minutes fire resistance. If the tank is at least 1.8 m away from the building and at least 760 mm from the boundary, the concrete slab alone will do just fine.

The oil supply pipes in this should be robust and fitted with a fire valve system. For the control of pollution, secondary containment may be required where there are positions with a significant risk of oil pollution. This will be either by means of integrated or constructed bunds.

In any case, information should be attached to the tank with instructions on what to do in case of a leak and the telephone number of the Environmental Agency.

LPG storage tanks will be controlled by the Health and Safety Executive, but small installations of up to 1.1 tonnes can be done following the guidance of the Approved Document. We are referred to UKLPG Code of Practice 1: Bulk LPG Storage at Fixed Installations Part 2 and BS 5482.

Besides this guidance, in simple terms, tanks should be in well-ventilated spaces, away from sources of heat and buildings. One firewall can be provided with a 30-minute fire rating, or 60 minutes if it forms part of the building.

If the tank is 3 m away from the building or the boundary, no special considerations are required. But if it gets closer to either, we are assisted with handy diagrams in the Approved Document.

LPG is heavier than air, so we need to make sure that if the tank leaks, it does not leak into basements, cellars, or drains.

Smaller bottles of gas can be located close to buildings, but there are, as ever, minimum distances required—away from windows, drains, etc. Pipes laid underground need to be corrosion-proof, but the pipe entering the building should be above ground, metal, and sleeved. Any pipes run in shafts, ducts, and voids should be ventilated.

Now, all there is to do is to fulfill the checklist from Appendix A, follow procedures from Appendix E, and give it to Building Control and the client.

So this is it, folks—The Approved Document J: Combustion Appliances and Fuel Storage Systems.

Let’s sum it up section by section:

  • Section Zero gives us the scope and standards for consideration. The Approved Documents primarily focus on domestic installations and cover combustion and fuel storage systems—including solid, gas, and oil installations—with specific output limits. In the text, we are further directed to seek guidance in the CIBSE Guide B and materials from BSI and IGEM.

  • Section One gives us general provisions for safe installation, which includes proper specification, material size, workmanship, and inspection. Adequate air supply, ventilation, and proper flue systems are essential for the good operation of the system. Specific requirements include carbon monoxide alarms for combustion appliances, and correct hearth sizing, heat insulation, and material selection. Proper documentation and compliance testing are mandatory.

  • Section Two adds the basics regarding solid fuel appliances up to 50 kW output, which require appropriate air supply, flue size and flue height. Flue outlet positions and distances from combustibles must be carefully considered. Clearances from walls and hearth specifications vary depending on appliance type and proximity to other combustible and non-combustible materials.

  • Section Three adds consideration for gas appliances up to 70 kW net input. They must be installed by a Gas Safe Registered professional. Room-sealed appliances are recommended for sleeping or bathing areas. Ventilation and through-flue requirements vary by appliance type. Considerations for outlet positioning and potential nuisance are made.

  • Section Four adds information on oil-burning appliances up to 45 kW output and follows similar guidelines to gas appliances but with specific provisions for all types and blends. Considerations are made for flue gas temperatures and their acidity, as well as positioning and hearth materials. The document emphasizes checking manufacturer specifications.

  • Section Five—oil storage and LPG storage must be protected from fire and environmental damage. Proper installation, secondary containment, and labeling for emergency procedures are required. Fire-resistant barriers or walls might be necessary based on proximity to buildings and boundaries. Guidance on underground and above-ground piping is provided.

 

In the next episode, we will move to Approved Document K: Protection from Falling, Collision, and Impact.

I hope you enjoyed this episode and that the considerations of Approved Document J: Combustion Appliances and Fuel Storage Systems make more sense to you right now.

If you have any questions, reach out to me on LinkedIn or send me an email—I'm more than happy to help you out.

At Bytnar, we deal with planning, designing, and managing your projects, and we are always glad to facilitate a free initial consultation to steer you in the right direction. Visit www.bytnar.co.uk and reach out to us—whether your question is "Can you help with my project?" or simply "What should I do?"—we will be able to give you a piece of non-obligatory advice.

At Bytnar, we help our clients design and execute their dream homes or investments. If your building is falling apart, we can also help investigate the reasons behind it and provide you with an appropriate strategy, design, and specifications for the repair.

Thank you again for listening. Please voice your opinions—I'm waiting for you on LinkedIn and I want to hear from you.

See you next week

Remember: Bytnar Designs The World Around You.

Toodloo! 👋



Piotr Bytnar picture on the circle background of Bytnar Wheel of Service

Piotr Bytnar BEng (Hons) MSc CEng MIStructE

Chartered Structural Engineer who deals with the Architecture of buildings. His Master's Studies led him to an in-depth understanding of risk and contract arrangements in construction as well as specialist knowledge in soil mechanics.

He and his team help homeowners and property developers to design and deliver construction projects reducing waste in time and the cost. He believes that the construction project is an iterative process that can be well managed and it is best managed if all the aspects of the project definition and management are dealt with in-house or coordinated by one organisation. His team works to all stages of RIBA and ISTRUCTE stages of work and enables contractors to deliver projects on-site providing risk evaluations, methodologies for execution of works and temporary works designs.



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