9" Cavity Block Vs Cavity Wall on Shed Build

paddydriver

Hello All,

Have been debating between Steel Shed Vs Prefabricated Concrete Vs Block Shed for some time. I am now getting quotes etc on them and obviously vastly varying pricing on each.

My main concern on steel is re condensation so have looked at the other 2 as options and steering towards a block built with hip roof.

Anyway, can cut some costs if I go 9" cavity block versus 2 x 4" cavity wall with insulation in the cavity. My mains questions are back to dampness and will the 9" cavity block lead to any dampness down the road? Considering it will have a scratch coat and sand and cement finish, I as hoping they would keep out dampness.

Any thoughts or is it worth going the extra €1.5k, or whatever final difference in cost is, to get the proper cavity wall?

Any help would be really appreciated as I am very new to this area

Thanks
Paddy

BryanF

what is the shed for - will anyone be spending time in it? what will its use be? you talk about condensation - were you planning to have a heat source in it?

paddydriver

Thanks BryanF, it will be mainly used for standard garden stuff and also all our bikes - some very good bikes and then the kids bikes. Lawnmower's and other gardening tools. Possibly paints too. The other thing is that I am in the process of getting a wood burning stove so will be storing a lot of kiln dried wood so this needs to be kept dry.

Won't be any living or office use etc. I may have a freezer in it down the road but for now won't be anything electrical.

Regards
Paddy

RITwing

You simply cannot beat blockworks for everyday wear and tear durability. If you have no heat genrating applicance in there why insulate at all?
Just ventilate well and you will have no condensation.

RITwing

paddydriver wrote: »

The other thing is that I am in the process of getting a wood burning stove so will be storing a lot of kiln dried wood so this needs to be kept dry.

Ventilate !

Introduction:
The HSE is issuing this notice to those who use, install, maintain or distribute wood pellet boilers or manufacture/store/distribute wood pellets. Since 2002 there have been at least nine fatalities in Europe caused by carbon monoxide poisoning following entry into wood pellet storage areas. Although there have not been any incidents so far in the UK the use of wood pellets is increasing and awareness of this danger is required. Wood pellet boilers are used in homes and businesses as an alternative to oil or gas fired boilers. They are also being installed to replace coal-fired boilers, particularly in schools.

Carbon monoxide can kill quickly without warning. It is a colourless, odourless and tasteless gas that is highly toxic. When carbon monoxide enters the body, it prevents the blood from bringing oxygen to cells, tissues, and organs.

Background:
Wood pellets are made from dried and milled sawdust and wood shavings that have been compressed into pellets, typically 10-20mm long and 3-12mm in diameter. They do not typically contain any additives or binders.

They are classed as a biofuel, a non-fossil heating fuel. The main countries of manufacture are Canada, North America and the Scandinavian countries within Europe. In 2000, the annual production of wood pellets in Europe and North America was about 1.5 million tons. This was expected to increase to around 16 million tons by 20111. Some wood pellet manufacture is now taking place in the UK.

Fatality details:
Fatalities caused by the release of carbon monoxide from wood pellets have previously been reported2 in Europe following personnel entering ships cargo holds (four) or storage silos (two).

Since 2010 there have also been three deaths caused by entry into wood pellet storage facilities in domestic sites3. Two were associated with a work activity and the other was a householder. In each case, the entry had been to resolve a technical problem. Details:

In January 2010, a 43-year-old engineer died in Germany after he opened a pellet bunker door. A second worker who was standing right behind him was also affected but still able to call the emergency services. The pellet bunker had a storage capacity of approximately 155 tonnes of pellets, supplying about 700 households.
In November 2010 a 38-year-old male householder in Ireland died after entering the 7 tonne wood pellet storage room for his boiler. His wife and another man were treated in hospital after trying to pull him to safety.
In February 2011, the 28-year-old pregnant wife of a caretaker, acting on his behalf, died in Switzerland after entering an 82m3 pellet storeroom that supplied 60 households.
Factors affecting the amount of carbon monoxide released from wood pellets
Wood pellets for boilers are normally stored in a large sealed hopper/tank or a storage room that has a screw feeder (auger) connected to the boiler. Alternatively, the hopper/tank can be mounted over the boiler for gravity feeding. Due to the enclosed nature of these hoppers/tanks/rooms, the atmosphere inside can become oxygen depleted and a toxic atmosphere containing carbon monoxide can accumulate. The chemical reactions responsible for carbon monoxide production from wood pellets are assumed to be an auto-oxidation process, especially oxidation of the fatty acids to be found in wood4.

Experimentation has shown3 that small quantities of wood pellets can produce life-threatening quantities of carbon monoxide in a confined space and that there are various factors that will affect the amount of carbon monoxide produced:

Age - pellets will produce more carbon monoxide within the first six weeks of being manufactured.
Temperature - more carbon monoxide is produced at higher temperatures.
Wood type - pellets made from pine contain more unsaturated fatty acids than spruce so produce more carbon monoxide.
Other factors - carbon monoxide levels will also increase with the amount of available oxygen present, exposed pellet surface area and amount of mechanical abrasion of the pellets that has taken place.
Note: In addition to the risk of carbon monoxide from wood pellets there is also a possibility of carbon monoxide being present because of a back-flow of flue gases via the fuel supply mechanism from the boiler. Causes for this include inadequate equipment being installed or a poorly designed flue.

Action required:
The HSE is advising all those who use, install, maintain or distribute wood pellet boilers and/or manufacture/store/distribute wood pellets to consider the following:

Wood pellet hoppers/tanks/storage rooms and boilers should always be installed and commissioned by a competent person, normally approved by the manufacturer/supplier. This is particularly important if the installation involves the replacement of a coal-fired boiler, where existing boiler room and storerooms are often utilised.
Do not enter the pellet storage area or place your head into a wood pellet hopper as they can contain toxic gases. No personnel should enter the hopper/tank unless fully trained and competent in confined space entry procedures. Controls should be put in place to ensure safe entry as per the HSE's Code of Practice for Working in Confined Spaces5. This should include adequately ventilating the storage area and checking carbon monoxide and oxygen levels with an appropriate device prior to entry. It is recommended that the store room is ventilated at all times, either mechanically or by being designed to have a through draught.
Ensure that the boiler and pellet feed mechanism etc. is cleaned and serviced by a competent person as specified by the manufacturers' instructions.
If any problems are encountered with the unit, such as the system not heating correctly or flue gas is flowing into the boiler room, turn the unit off and contact the supplier and/or manufacturer and request assistance.
Duty holders who store wood pellets, particularly in bulk should have a suitable risk assessment and safe system of work in place.
Manufacturers, suppliers and distributors of wood pellets should provide adequate health and safety information to the user in their materials safety data sheet.
Warning signs should be placed on the pellet storage area access door, ideally on both sides so it can be seen when the door is open. The warning sign should include the following information:
DANGER - RISK OF CARBON MONOXIDE POISONING - There is a danger to life from odourless carbon monoxide and lack of oxygen. Check atmosphere before entry with an appropriate device. No entry for unauthorised persons. Keep children away from the storeroom.
No smoking, fires or naked flames.
The room should be adequately ventilated before entering. Keep the door open whilst inside.
There is a danger of injury from movable parts.
Filling procedures should be carried out accordance to the instructions of the heating installation company and the pellet suppliers.

source

paddydriver

RITwing wrote: »

You simply cannot beat blockworks for everyday wear and tear durability. If you have no heat genrating applicance in there why insulate at all?
Just ventilate well and you will have no condensation.

Hi RITwing, so you are you saying the 9" cavity blocks will be fine? I have nothing I need to keep heat in for, I just want to have a decent atmosphere in there for storing all my kit. I don't plan on finishing the interior walls either.

During the worst of the winter cold around 2010 I did have issues of paints freezing in my barna sheds and ideally would like to avoid that again but most I have talked to said that unless you have some heat in there then that can happen in any shed build if temp's go low enough outside - even having a freezer running in there would help generate the little heat needed to prevent that happening.

Thanks for your help
Paddy

BTW.. see your other post re wood pellets. No plan to use them at all, just regular kiln dried logs. Will have good carbon monoxide alarms in the area the stove will be in too. Not taking any chances! Thanks for info.

RITwing

So long as you don't store delicate or persishables ( no clothing , no important papers or books ) you will be fine with rendered non insulated blockwork. Use 215 solid so that way you have good anchorage for fixings shelves if you need it.

paddydriver

RITwing wrote: »

So long as you don't store delicate or persishables ( no clothing , no important papers or books ) you will be fine with rendered non insulated blockwork. Use 215 solid so that way you have good anchorage for fixings shelves if you need it.

Hi RITwing, am guessing the 215mm applies if going with the cavity wall? If going 9" cavity block can I put light use shelving up?

Thanks,
Paddy

RITwing

Sure - best to use a system with legs then so the floor really does the supporting. you are just then tying back to the blocks to stop the toppling

galwaytt

Why not timber framed? Light and warm, won't condensate. Exterior finish can be conventional plaster or any number of modern finishes.

matrat

galwaytt wrote: »

Why not timber framed? Light and warm, won't condensate. Exterior finish can be conventional plaster or any number of modern finishes.

Would be interested in a rough spec on this, looked at this option but seemed to be more costly than block when all was considered. What is the conventional way to plaster timber frame also?

galwaytt

matrat wrote: »

Would be interested in a rough spec on this, looked at this option but seemed to be more costly than block when all was considered. What is the conventional way to plaster timber frame also?

You don't plaster timber directly. You can put battens on a timber structure, cement-board it, and then plaster that if you like, and it'll look the same.

In any construction if cost is the ultimate arbiter, then you are going to have to put up with the limitations of what the price gets you: as you say, condensation, or insulation or......(whatever).

And if dampness and condensation are as important to you as they seem, you should budget accordingly to not have it

paddydriver

Thanks all for input.

Have got pricing back now on just the 9" cavity block build with scratch coat then sand and cement, which I am guessing is the standard block shed build?

Based on what I have got now there are massive variations between what some builders charge for what is a fairly standard spec.

I think at this stage it will be just the single 9" cavity block with the hip roof. Have been given options of raft or strip foundations. Floor will be poured with all relevant damp proof included.

Any thoughts re the foundation type? Differing builders seem to have their own preferences and recommendations but I was always familiar with the standard strip foundations.

Thanks
Paddy

BryanF

paddydriver wrote: »

Any thoughts re the foundation type? Differing builders seem to have their own preferences and recommendations but I was always familiar with the standard strip foundations.

im afraid we cant discuss structural items here

paddydriver

BryanF wrote: »

im afraid we cant discuss structural items here

Hi BryanF.. is that not what we have been discussing up to now anyway

BryanF

paddydriver wrote: »

Hi BryanF.. is that not what we have been discussing up to now anyway

From the forum charter which I'm sure you have read;) but please allow me direct everyone's attention to the following sections:

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1.5 Structural items . Issues relating to the specification of structural components is prohibited. Any queries in this regard need to be dealt with by an architect/engineer privately.

2.2 Do not argue with a mod or dispute his/her instructions on thread. If you have an issue send a Private Message to the moderator .

Whilst advice might be sought/given in this forum, posters should make every effort to verify advice expressed herein with a suitably qualified independent third party who possesses the appropriate Professional Indemnity insurance cover. The advice and opinions expressed on this forum are not those of boards.ie Ltd. and the management accepts no responsibility for what is written and posted here.

darragh_haven

paddydriver wrote: »

Hi BryanF.. is that not what we have been discussing up to now anyway

Paddy. It's basically if I said you should use foundation tye A, and you used it and it failed, your wall cracked and fell down (and god forbid, some gets seriously injured). You might be able to try and trace me and try and claim against me..... therfore I can't give structural guidance

galwaytt

paddydriver wrote: »

Thanks all for input.

Have got pricing back now on just the 9" cavity block build with scratch coat then sand and cement, which I am guessing is the standard block shed build?

Based on what I have got now there are massive variations between what some builders charge for what is a fairly standard spec.

I think at this stage it will be just the single 9" cavity block with the hip roof. Have been given options of raft or strip foundations. Floor will be poured with all relevant damp proof included.

Any thoughts re the foundation type? Differing builders seem to have their own preferences and recommendations but I was always familiar with the standard strip foundations.

Thanks
Paddy

If I may, there's no such thing as a 'standard' garage. If you're only putting bicycles and lawnmowers in it, that's one thing.

If it houses your garden-furniture, your wood-pellets, you'll need a 'better' one.

If you're putting your vintage car or shiney Harley in it, you'll def need a better one again. (and I've see a lot of nice vehicles destroyed by poor garages...they've have been better off outside...)

The list is endless. You should build that which matches it's actual end use, and then get the price for that.

Otherwise it's not even apples v oranges you're comparing, it's Fruit versus Veg !! :pac::pac:

Me ? if it doesn't have insulated floors, tiled (really), walls, roof and proper - sealed - doors, I won't even go into it. But that's just me - YMMV and all that

paddydriver

I have worked my way up from considering a Steel Shed to a Block Shed, in between was a prefabricated concrete shed - http://www.irishconcretebuildings.ie/

I just cannot convince myself as regards condensation issues with steel sheds as they seem hit and miss and no two builds seem the same. I liked the idea of the prefabricated shed but the finish on them just doesn't appeal to me. They do an option of a steel tile effect roof and it seems to have a decent vapour barrier in between but again I am wary of steel. Now based on quotes I can get the block shed for little over €2k more.

I think the driest and most secure option will be the block shed and also it will be finished with a proper roof and I can paint it to match the house. If I go with block then it will be closer to the house due to being able to match it up whereas other options were going to be down the garden.

Going to chat to the builder tomorrow and get better idea on the exact spec of the build. Might be back then for more thoughts;)

Thanks All
Paddy

just do it

Paddy
I reckon go with the empty cavity as it will give you the option of insulating at a future date. Maybe you might move and it could be a selling point for a prospective buyer. What these sheds are used for can change over time. Even your own needs could change. Maybe you'll have a child who takes to the drums . Maybe you'll want to convert it. Maybe you'll want to extend it and make it a granny flat. The relatively small extra outlay now will give you options.

paddydriver

just do it wrote: »

Paddy
I reckon go with the empty cavity as it will give you the option of insulating at a future date. Maybe you might move and it could be a selling point for a prospective buyer. What these sheds are used for can change over time. Even your own needs could change. Maybe you'll have a child who takes to the drums . Maybe you'll want to convert it. Maybe you'll want to extend it and make it a granny flat. The relatively small extra outlay now will give you options.

Thanks, will run it past builder tomorrow as regards extra cost involved in going for a cavity wall. Space wise I don't see this being bigger than around 140 sq ft so likely will just be for the bikes and gardening kit.

just do it

Another thing to add if you're thinking of future proofing is floor insulation. I've 100mm in my floor, 1st course of quinlite, and 150mm cavity. Most likely now that I've done all that it will always and forever be a non-heated shed! However should I decide, a simple storage heater would do wonders during the worst of weather (assuming wall and roof insulation has been added).

sky6

I built a garage using double leaf 4 inch blocks on edge with a 5 inch cavity between. I also Insulated the Floor with 4 inch Polyiso. I used double glazes pvc Windows and an insulated Garage Door.
The best thing I've ever done. I had intended to insulate between the walls but it's not necessary.

in my last House I also built a Garage using 9 inch Cavity Blocks. It was always cold in Winter and all my Tools rusted after a few Winters in there.

paddydriver

Hi Sky6, how does the floor insulation work? Was looking at the Polyiso and wondering does this actually sit under the final concrete floor? Got a good doc on the Xtratherm website that seemed to indicate this was the case.

What you have done likely wouldn't cost massive more for me to do so will look into.

Appreciate the info.

Paddy

sky6

Yes, I poured the concrete on top of the insulation and steel reinforcing. Kingspan is excellent to use. It just happened that I was offered some polyiso a friend had over from his build.

hesker

just do it wrote: »

Another thing to add if you're thinking of future proofing is floor insulation. I've 100mm in my floor, 1st course of quinlite, and 150mm cavity. Most likely now that I've done all that it will always and forever be a non-heated shed! However should I decide, a simple storage heater would do wonders during the worst of weather (assuming wall and roof insulation has been added).

If you did build something like this to house that shiney Harley would you still need a heat source to stop it slowly rusting away. Would you end up having to regulate the temperature almost the same as in a domestic dwelling?

just do it

hesker wrote: »

If you did build something like this to house that shiney Harley would you still need a heat source to stop it slowly rusting away. Would you end up having to regulate the temperature almost the same as in a domestic dwelling?

Going by sky6's experience the answer is no. Dampness is the issue regarding rust. However some heat would do no harm and it needn't be as regulated as the household. A storage heater for example. Come back to me in 2 years and I'll be able to report from experience then!

keano25

just do it wrote: »

Going by sky6's experience the answer is no. Dampness is the issue regarding rust. However some heat would do no harm and it needn't be as regulated as the household. A storage heater for example. Come back to me in 2 years and I'll be able to report from experience then!

Well, how did you get on?