stunotch Posted September 27, 2022 Share Posted September 27, 2022 Hi, I'm planning to build a concrete block workshop at the end of my garden, replacing a rotten old wooden shed. Although I would consider myself to be more than competent at general building work, I have never built a building from scratch, so would like some advice! I currently have an old concrete slab which is a bit broken and cracked, but I believe will make a reasonable base to eventually pour my new floor slab on to. (Photo attached) The workshop will be 4m X 4m, with a door on one side and a window to the front, I also want it to have a pitch roof. Questions I have so far!: How deep should footings be? The land has quite solid bedrock about a foot under the topsoil !! I will be putting a DPC sheet across the existing concrete slab, with insulation on top before pouring my concrete floor, how thick should the insulation be? and how thick should the concrete floor be? How high above the new finished floor level should the first courses be before putting the DPC in? I was considering building a cavity wall to prevent damp, as I will be storing tools I didn't want them getting rusty etc., however this would increase the cost quite a bit, so I am now considering using hollow concrete blocks instead. Would this be a reasonable alternative? I read they offer a much higher insulation value than single blocks? If I do use hollow concrete blocks (440x215x215), with the wall length of 4M, does this mean I wouldn't require piers? Do I need to work from detailed plans? As a small 4M square building is there anything I would need to have calculated? Or should this be a straight forward build. How do I decide on the roof pitch? Any other tips / help would be much appreciated. Thanks. Link to comment Share on other sites More sharing options...
joe90 Posted September 27, 2022 Share Posted September 27, 2022 43 minutes ago, stunotch said: I was considering building a cavity wall to prevent damp, as I will be storing tools My workshop is single skin block with render outside, no damp and no rusty tools. Link to comment Share on other sites More sharing options...
joe90 Posted September 27, 2022 Share Posted September 27, 2022 44 minutes ago, stunotch said: How do I decide on the roof pitch? Depends on what roofing materials, tiles, slates, felt, GRP? Link to comment Share on other sites More sharing options...
TonyT Posted September 27, 2022 Share Posted September 27, 2022 Is this under permitted development? Link to comment Share on other sites More sharing options...
stunotch Posted September 27, 2022 Author Share Posted September 27, 2022 34 minutes ago, joe90 said: My workshop is single skin block with render outside, no damp and no rusty tools. Good to know. Link to comment Share on other sites More sharing options...
stunotch Posted September 27, 2022 Author Share Posted September 27, 2022 34 minutes ago, joe90 said: Depends on what roofing materials, tiles, slates, felt, GRP? Was planning on a slate roof, to match what is on the house. Link to comment Share on other sites More sharing options...
stunotch Posted September 27, 2022 Author Share Posted September 27, 2022 33 minutes ago, TonyT said: Is this under permitted development? Yes it is within permitted development, but the building already appears on the title deed also. Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2022 Share Posted September 28, 2022 Plough through this. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/830643/190910_Tech_Guide_for_publishing.pdf#page41 Link to comment Share on other sites More sharing options...
ProDave Posted September 28, 2022 Share Posted September 28, 2022 10 hours ago, stunotch said: Was planning on a slate roof, to match what is on the house. I would be surprised if you can get a roof pitch steep enough for slate and still remain in the permitted development ridge height limit. Link to comment Share on other sites More sharing options...
Conor Posted September 28, 2022 Share Posted September 28, 2022 10 hours ago, stunotch said: Yes it is within permitted development, but the building already appears on the title deed also. You're limited to a ridge height of 2.5m as you are within 1m of a boundary. I think, like mine, you'll be limited to a flat roof. I would be worth digging out the existing concrete and pouring new footings and a slab. An extra weekend of work with a micro digger. Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2022 Share Posted September 28, 2022 8 minutes ago, ProDave said: I would be surprised if you can get a roof pitch steep enough for slate and still remain in the permitted development ridge height limit. Oh I don’t know, mine is steep enough for slate, 2.5m eaves and 4m fir dual slope roof ridge 🤔 “I also want it to have a pitch roof.” Mono or dual? And it’s only 4m ! Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2022 Share Posted September 28, 2022 1 minute ago, Conor said: You're limited to a ridge height of 2.5m as you are within 1m of a boundary. Ah, missed that . 😴 Link to comment Share on other sites More sharing options...
ProDave Posted September 28, 2022 Share Posted September 28, 2022 If you want the full 4M ridge height under permitted development, then you have to move the building. It probably needs planning permission, and it won't help you now, but the advice would have been apply for PP for the replacement workshop BEFORE you dismantle the old one. 1 Link to comment Share on other sites More sharing options...
Carrerahill Posted September 28, 2022 Share Posted September 28, 2022 11 hours ago, joe90 said: My workshop is single skin block with render outside, no damp and no rusty tools. I can second this as mine is the same. The only issue I ever get is when its been quite cold for a few days, and the outside air temp rises, the garage/workshop remains colder, a dry cold, you then open a door and a rush of warmer damp air enters the garage, I then sometimes get condensation on big metal objects, the Land Rover 90 being one of them and my tool safe, however, this phenomenon only ever happens about 6-8 times a year and can be limited by entering the garage and shutting the door. I had considered forced ventilation on a humidity stat but I also then decided that warm humid air was the last thing I wanted coming in! 1 Link to comment Share on other sites More sharing options...
stunotch Posted September 28, 2022 Author Share Posted September 28, 2022 I have recently had planning permission approved for a large double storey side extension on the house, went through with no issues. The neighbour has a 7x8M double storey garage right next to the boundary where I want to build mine, and a new housing estate that is being built in the field behind my house is building a double garage with pitch roof directly behind my boundary wall where I want to build mine. So I can't imagine there would be any issues at all getting planning for a pitch roof. I will contact the planning officer to discuss it and see what he says. Either way, I can still get on with the ground works, if it is simple enough to get planning I will do, if it isn't straight forward then I can change the roof design to keep within the 2.5M I plan to hire a micro digger to do the footings, Above I see @Conor suggested removing the old slab. There was a few reasons I though it best to keep it there, despite it being a bit cracked and old, I thought it might provide a solid base? Then there is the issue of removing the old concrete waste and having to hire a bigger skip, more cost etc, and where the workshop is being built is at the end of our garden which is quite long, so quite a number of wheelbarrows up and down the garden to remove it all! However, as I said, I am a novice to this, and if the advice is that it is best to remove the concrete and start again then I will do. Thanks all. Link to comment Share on other sites More sharing options...
stunotch Posted September 28, 2022 Author Share Posted September 28, 2022 What are peoples thoughts on using the hollow blocks? and would this mean I wouldn't require piers? Thanks. Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2022 Share Posted September 28, 2022 Piers fir a single skin wall are required every 3m so you would need one in each of your 4m walls, or you could place them to match windows or doors. Link to comment Share on other sites More sharing options...
stunotch Posted September 28, 2022 Author Share Posted September 28, 2022 20 minutes ago, joe90 said: Piers fir a single skin wall are required every 3m so you would need one in each of your 4m walls, or you could place them to match windows or doors. Thanks, and would this be the same if I opted to build using hollow concrete blocks? Link to comment Share on other sites More sharing options...
Iceverge Posted September 28, 2022 Share Posted September 28, 2022 1 hour ago, joe90 said: I also want it to have a pitch roof. The minimum pitch will be normally supplied in manufacturers instructions for the roofing material. How do you plan on bringing in the concrete for the shed base? Wheelbarrowing it is a real pain and would require a team of workmen. This came to mind from the distant reaches of my noggin. It is an advertorial for a Bricky tool ( I have no experience of it ) but it details an entire build of a small workshop. The engineering is very much rule of thumb but to be honest but the finished building looks well. Probably 90% of houses still standing are built using rules of thumb. https://youtu.be/NJ4-cO8Uv0g Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2022 Share Posted September 28, 2022 18 minutes ago, stunotch said: Thanks, and would this be the same if I opted to build using hollow concrete blocks? I can’t find the proper info on this but if I remember correctly you won’t need pillars for a hollow 9” wide block wall, you might not either fir a 6 inch? Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2022 Share Posted September 28, 2022 Ah here it is (I think) skip to page 39…..https://www.labc.co.uk/sites/default/files/EXT.Approved-Document-A-Structure.JMCN_.v1.030417.pdf Link to comment Share on other sites More sharing options...
stunotch Posted September 28, 2022 Author Share Posted September 28, 2022 27 minutes ago, joe90 said: Ah here it is (I think) skip to page 39…..https://www.labc.co.uk/sites/default/files/EXT.Approved-Document-A-Structure.JMCN_.v1.030417.pdf Ah thanks, that's really useful. So it would be an advantage to build using hollow blocks as I would have no need for internal piers. Although I imagine laying hollow blocks is probably more fiddly than standard blocks when putting the mortar down? Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2022 Share Posted September 28, 2022 1 hour ago, stunotch said: I imagine laying hollow blocks is probably more fiddly than standard blocks when putting the mortar down? Different but not difficult. Link to comment Share on other sites More sharing options...
PeterW Posted September 28, 2022 Share Posted September 28, 2022 Why not just build with 140mm blocks..? Quick and easy and tbh they are nicer than hollows and you don’t lose the internal space of a 9” block 1 Link to comment Share on other sites More sharing options...
Carrerahill Posted September 28, 2022 Share Posted September 28, 2022 On the hollow block topic, I have never actually seen them for sale in the flesh and I frequent merchants as often as I do supermarkets. I've seen them come up on Travis Perkins website - they also seem pretty expensive given they are only thicker and offer no additional height or width. So, is there regional availability differences of these? I can also say that in my professional life which often finds me on sites, I don't believe I have ever spotted hollow block. I see it a lot on YouTube videos, mainly North American builds. Can anyone offer any insight into these, to me, unobserved blocks? The only time I think I might consider using them was for a garden wall where I wanted to have a single skin but appear thicker. But, at the price, I would be cheaper building a 4" cavity wall. I can also see the benefit if I wanted to build a near bomb-proof structure, I could fill the hollows with concrete. Link to comment Share on other sites More sharing options...
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