i want to build a shed in the garden,i have the slab down already and was going to use blockwork for the walls and stick insulation backed plasterboard on the internal walls,is this ok to do as i have been told that i need a cavity wall to keep out any damp?thanks
shed
- Thread starter spoonse
- Start date
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You want a shed to be warm and dry.
You want it to be quick and easy to build.
A shed made of waterproof plywood will do all this for you.
Keeping warm is really about keeping the wind out, there is also the other side of the problem keep cool in the summer.
A shed made with 9mm ply and lined with 2 inches of polystyrene will do this,
use 18mm ply for the floor with 2 inches of polystyrene under to keep your feet warm.
You want it to be quick and easy to build.
A shed made of waterproof plywood will do all this for you.
Keeping warm is really about keeping the wind out, there is also the other side of the problem keep cool in the summer.
A shed made with 9mm ply and lined with 2 inches of polystyrene will do this,
use 18mm ply for the floor with 2 inches of polystyrene under to keep your feet warm.
The cavity isn't there to keep out damp, it's primary function is to prevent heat loss through the walls but a cavity would help guard against condensation problems inside the shed.In particular interstitial condensation seeing as you're using insulation backed plasterboard. It all depends on how you intend to clad or finish the blockwork. Blocks are highly porous so unless you provide them with an impermeable finish then the chances are you'll have problems with damp.
The question is, what you intend to use it for? If it''s just for storing a few garden tools then I wouldn't worry too much.
The question is, what you intend to use it for? If it''s just for storing a few garden tools then I wouldn't worry too much.
well i am going to use it as a music room/games room etc,somewhere to escape really at the moment i have a ply/studwork shed there already and like you say it has a high humidity reading sometimes all to do with the environment but i have an allergy to something in there and have to pull it down unfortunately and wanted to use other materials.Have thought to render the outside of the blockwork if i could ,so a cavity wall would be a lot better then?
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If you're going to use it as a habitable room then yes, a cavity wall would be a lot warmer. The blocks should be fine if you render them though.
It's up to you, 50, 75 or 100mm... the bigger the gap the better but just remember you'll have to increase the number of wall ties used if you go above 75mm.
i find it really strange why people call this sort of building a shed. I certainly wouldn't describe my house as a shed thats bricks and has got a cavity.
Is there any way you may be describing it as a shed as you think you will get around planning permission and building regs? i really am just curious thats all.
Is there any way you may be describing it as a shed as you think you will get around planning permission and building regs? i really am just curious thats all.
Sorry Joe, completely wrong, cavities were designed to prevent moisture penetration, indeed a solid wall which they replaced is far more efficient in retaining heat than a cavity wall.
Yes, that's why the building regs are demanding increasingly bigger cavities! Water just keeps getting wetter!
Ever since the Price of Wales built a garden shed that was like an expensive bungalow there has been an explosion in garden sheds.
You only have to tour the likes of Hounslow to see the luxury garden sheds in all their glory (complete with their tenants)
Sorry that a plywood shed doesn't suit.
Lets look at high humidity. High humidity is caused by a sudden drop in temperature. Warm air holds more water vapour than cold air, when you turn the heating off, the temperature drops, the air cannot hold the same amount of water vapour so it condenses on the nearest cold surface, usually a cold window, next a cold wall, floor or ceiling. Water vapour is usually put into the air by our breathing (we breath out about 2.5 litres of water every 24 hours) and accumulates due to lack of ventilation. It is easily stopped by using a de-humidifier that removes the excess water vapour.
Cavity walls. These came about due to poor brick laying, brick walls are full of thousands of small holes. When it rains hard and the wind blows, it pushes rain through the walls. People got feed up with water running down the inside of their walls, spoiling their decorations. Cavity walls allow the rain to run down between the walls, leaving the inner wall dry.
Blocks. These usually stay dry (if block laying is as bad as brick laying the rain will come through the mortar) Rain makes the surface wet but, it soon dries out. If rendered then they can have problems. Why?
Humidity/water vapour always moves to wards cold, water vapour in a room will move into the walls (through a plasterboard ceiling or wall) making its way towards the cold outside. Inside the wall it can freeze (this will not harm a block wall) unless it is rendered, where the water vapour arrives on the outer edge of the block, under the render freezes and starts to push the render off.
You only have to tour the likes of Hounslow to see the luxury garden sheds in all their glory (complete with their tenants)
Sorry that a plywood shed doesn't suit.
Lets look at high humidity. High humidity is caused by a sudden drop in temperature. Warm air holds more water vapour than cold air, when you turn the heating off, the temperature drops, the air cannot hold the same amount of water vapour so it condenses on the nearest cold surface, usually a cold window, next a cold wall, floor or ceiling. Water vapour is usually put into the air by our breathing (we breath out about 2.5 litres of water every 24 hours) and accumulates due to lack of ventilation. It is easily stopped by using a de-humidifier that removes the excess water vapour.
Cavity walls. These came about due to poor brick laying, brick walls are full of thousands of small holes. When it rains hard and the wind blows, it pushes rain through the walls. People got feed up with water running down the inside of their walls, spoiling their decorations. Cavity walls allow the rain to run down between the walls, leaving the inner wall dry.
Blocks. These usually stay dry (if block laying is as bad as brick laying the rain will come through the mortar) Rain makes the surface wet but, it soon dries out. If rendered then they can have problems. Why?
Humidity/water vapour always moves to wards cold, water vapour in a room will move into the walls (through a plasterboard ceiling or wall) making its way towards the cold outside. Inside the wall it can freeze (this will not harm a block wall) unless it is rendered, where the water vapour arrives on the outer edge of the block, under the render freezes and starts to push the render off.
which came first cavity walls or wall insulation? they were first used to keep out water. Now they have a dual purpose, but without insulation the size of the cavity wont make a great deal of difference to heat retention.
Theres no denying that cavity walls have a dual function but their primary function is to increase the buildings thermal resistance. We have hundreds of thousands of properties in this country without cavity walls which perform perfectly well and don't suffer from problems with penetrating damp. If anything these properties are more likely to suffer from condensation damp due to cold bridging, building cavity walls helped reduce this problem far more than issues with penetrating damp. The incidence of penetrating damp has always been relatively minor in relation to condensation damp.
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