Lets Talk Concrete Blocks

Martynt74

Martynt74

Martynt74

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Joined
20 Feb 2004
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Hondon de las Nieves, Spain
I'm trying to work out a price to build a garage/workshop structure, for a new house we're looking at. I was initially thinking of a timber frame but have been looking more into blockwork to see how the costs compare.

In theory the structure will be around 8m x 3m (ish). Probably split into 2 sections, one for a workshop and possibly one for a cinema room or gym. Planning permission will be sought if needed. Although i'm thinking walls at 2m and then a slight pitch to the roof to stay under 2.5m. Just need to work on drawings to decide whether the pitch would be enough for such an area.

The plan would be to take my time, build it myself and learn some good skills. Possibly taking a 2 day bricklaying course to learn a few tips. Although youtube also comes in very handy.

Obviously the foundation/sub base will need to be much thicker if making from concrete blocks due to the weight.

I'm also trying to decide the best size of blocks to use. I presume if i was to go single skin, i'd be better using 440x215x215 blocks as they'll be much more sturdy. But if i went for 140mm blocks and built piers every 3m then would that also be suitable?

Also, whats best between solid dense blocks, hollow blocks and thermalite?

I imagine i will have LOADS of questions so going to use this as a sounding board thread. I did try reading a few others on the forum but they're old and all pictures have gone :(


I've just done a block calculator and it's suggesting that for my structure, i will need 434 215mm blocks. Does that sound about right? That would suggest the build for the main structure would be about £2k

My theory is to aim for around 6-7k in total, if doing most of the work myself (bar plastering!)


The dad of one of the house sellers is an Architect. Wonder if he'd knock me up a drawing for free if i bought their house!
 
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I say go ahead and do it in brick, I was in the same boat I hate been ripped off by builders, so let's fast forward 6 years I have a built my own conservatory with a full hight wall and dwarf, and front porch looks great If you don't mind me saying lol

1 week before this I never layed 1 brick in my life :)

I used thermalite blocks for inner skin.

For the roof see if you can angle from front to back and use rubber roofing it's amazing stuff.

Foundations in my garden where fine at 1 meter deep can depend on surrounding trees etc I personally think it's over kill with some regs , going back many years some house where on built on a few inches of foundations lol
 
Yeah we used rubber roofing on our bay window, seems very good but was damn expensive. It's quite an old house so thinking tiles would fit better too.

I suppose you're right about just angling the roof but over a 3 metre span i'd only have a 10 degree angle, whereas with a pitched i could get around 15 degrees which i'd have thought would be about the minimum you'd want.
 
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The quantity sounds like it might be about right. If I remember rightly, it’s 10 blocks/m2. I’d be tempted to use two skins of 100mm blocks rather than 215mm blocks... it’ll amount to the same and they’ll be a load easier to work with.
 
with 140 block I'd be surprised if you needed piers, it's pretty substantial! Also remember you are going to be lugging the things around so remember the weights of them if you're not used to it.
Timber frame would be quicker for a self build, or at least quicker to get it wind and water tight...
 
Yeah that’s a good point. It’s likely to be near summer time anyway as we’ve not even bought the house yet!

Was hoping it could be a month long project or so. Figured I’d take a week off work to dig out the foundations and then figured it would be best to get a company in to pour the concrete rather than attempt myself as it’ll be a pretty big area to tackle myself.

Then if I can get the walls up in the same week I can tackle the roof the week later in evenings.

Is single skim safe enough then using 140mm blocks?

I’m also thinking that internal height may be an issue. What are people’s thoughts on excavating slightly and having the floor about 30cm below ground level. That would keep the total height under 2.5m but give reasonable headroom inside for me (about 195cm).

Otherwise I may apply for planning permission for a taller structure.
 
From a roof truss point of view. I'd prefer a bit more ceiling height. I presume something like Scissor Trusses would be the way forward here?

Also, if i was to excavate down slightly for the floor, what extra things do i need to consider? Other than further digging. I'd be looking for the entrance to still be at ground level but then with a step down into the room.

Also Also - Given i'll be using footings for the foundations, what kind of thickness will i need the main subfloor to be? I presume as it wouldn't be bearing any weight it doesn't have to be too thick?

Do i even need a concrete subfloor or can i just suspend joists for the floor?
 
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I wouldn't go down personally, ahem ;) , at least not without having to rule out other options first

Means getting anything semi heavy or above in out will be a pain, its always a trip hazzard etc etc

Suspended joists you could do, you have to dig down then though to give the clearance and its going to be harder to get airflow underneath without your suspended floor ending up above ground level, not impossible, but harder

This is why an all timber construction becomes easier, foundations are minimal, you have a slightly suspended floor by default, giving the required ventilation to the floor.
I am slightly confused though as to if this is a garage or a workshop. If its a garage/workshop from the perspective you would be taking a car in then your pretty much going to have to go solid floor.

If its a workshop that you within reason will only be taking things you can "carry" in, then thats a significantly lower requirement
 
This sort of thing sounds like it meets your requirements?

http://logcabins.co.uk/products/mr-talbots-workshop/?portfolioCats=240,241,242,243,244,245,246,247,248

I am sure someone told me the roof height issue is slightly more complex that its made out to be, as in the 2.5M applies, but if the roof gets higher once 2M away from the boundary you can go to the higher height, ie it cant be higher with 2M but the same roof can get higher the further you get away, i think he even mentioned an angle he had to comply with, I am fairly sure i remember who it was so i will ask him

You would probably want to check that out, as with a cabin/building the size your after a 3M height (such as above) may be achievable


edit to say, I love that workshop so much it makes me want to move to get the space that I could have one as well :)
 
Cheers @Mercenary Keyboard Warrior. I have read that about the height barrier so if i was to angle front to back then as you say it could be higher at the peak as long as it's 2m away. Considering i'll have to keep a gap from the boundary fence of around 1-2ft for maintenance and for the run-off to land in my garden rather than the neighbours anyway then that's a chunk of the 2m gone straight away.

Going down is probably a last resort, i did speak to the planning officer who said that if i was only talking about a small extra height above 2.5m, say 3m and if it's just the peak of the roof that would be above that then she'd see no issue with planning should i go down that route.

Just to confirm, it's a workshop/possibly home cinema combined. Depends how big i can get away with making it really.

That wooden cabin does look pretty good, then do a design your own option too so will look into that more.

Mentioned a budget of around 9k to the wife last night from some very rough back of a fag packet guesswork. Apparently she was thinking closer to 3k!

Granted i've got about £1k worth of tools (most of which i don't really need to build this but if i can get away with it then superb!)


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Foundations - Cost to get ready mixed concrete poured in. Very rough estimate and could be well wrong. Could be saved on by doing myself.

Main Structure - As above - Assuming a £2/brick cost and 450 bricks, plus various bags of sand/cement (Includes 15% Contingency from calculations)

Roof - Again, absolute guesswork at this stage - Assuming getting trusses made offsite. Shouldn't be hard to build myself though. Price includes plywood for boarding and shingles.

Floor - As per the foundations, got about £500 to get ready mixed poured in. Then about £1000 for plywood and joists and then a finishing laminate

Ceiling - Insulation and Plasterboard.

Interior Walls - As per the ceiling really

Electrics - Basic wiring and sockets. Have since added an extra £200 to include an RCD and getting it signed off. There's already cabling to an existing shed which is handy.

Doors/Windows - Could probably be saved on by picking up used stuff.



Most these figures are based on me making them up, very little substance to them so i'd appreciate it if people could advise if they sound reasonably ballpark :)
 
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I'm currently building a massive extension on my house, mainly the properties in my area priced my folks out, to be near to me and the grand kids, hence building this 'extension' where we hopefully get the best of both worlds! They get a double bedroom each, my two girls get a double each, my missus and me get the loft and extension so large master / walk in ward/ spa bathroom and double guest on top floor. 2 shower rooms to service the first floor. My folks get our old lounge, with just 2 chairs in it will be very spacious, even with bookcases lamps etc. We get a 4000 x 7000 lounge, kitchen that's 6000 x 5000 and a utility room for washing machine chest freezer boiler etc. Also a wetroom following on from the utility, (my dad suffered a stroke several years back and gradually getting worse) We budgeted 150k, we have the money no problem, jesus is the building industry a joke..

OP you seem a bright chap, not afraid of some graft and learning from the mighty web! First thing I suggest you do, is look up your local councils permitted development rules.. for Birmingham, it was a pdf of 50 odd pages, however, I was able to understand lots more of what I can get, rather than my 'architect' who was still quoting figures from 8 years back. See exactly what your council will allow, it does vary quite a bit depending where you live and if you are on an estate or in the countryside etc.

I watched them doing the foundations, in fact I did some many moons back as a labourer in the summers back from uni, ready mix was a killer! The foundations now for single story up to 2.5 in Bham have to be min of 1000mm then usually two course to bring to floor level. Basically my builder has used a 300mm block on the bottom, then used 2 courses of blocks (thermalite on inside course) with a 100mm gap for the insulation between. My build was massively difficult as I had a main sewer running next to my house which the extension of 2 stories was going over. Severn trent did their nut, birmingham city council did theirs, and my builder had to pick up the pieces, ended up digging 11 foot foundations and shuttering the sewer pipe, it was only a 150mm as well!!! That pipe has cost me near 6k so far :(

Trust me, do your reading, it'll help plenty, maybe even save some cash! (chance will be a fine thing) If I was building a project your size you defo have to have a double skin with insulation, I'd also go for concrete floor. Just get the concrete for foundations and floor delivered, save your back, you'll need it for the roof! Best of luck mate, and look out for the weather!
 
I am literally in the same boat as you op.
Looking to build a 5m x 6m garage, was only going to go single skin though, pitched roof, sectional door at the front and a side door.
Think I could build it for £3k but I don't need the tools, or the finish you do... Breeze block finish is fine, a few sockets, 2nd hand doors...
 
Will be interested to follow if you do a build log then.

My tools aren’t really needed for the build. They’re mostly just things I’d like which I thought I’d try and pass off as building cost. Like a table saw and nail gun!

After seeing build on amazing spaces I like the idea of cladding the outside in scaffolding planks which I know can be bought reclaimed easy enough.

It’s mainly the concrete for the foundation at this stage. Need to look into buying a used mixer I think.
 
Haha give me your mixer then :p

I was working on the basis of around 15m3 of concrete so i figure i can do it myself for around half the cost of it being poured. Just a bit nervous about getting doing it quickly enough to avoid the bottom drying out before i fill it up.
 
True, not arsing around with shoveling and running the risk of the materials getting wet outside is a big plus. However my wife has gone from changing a few kitchen cupboard doors and a new oven to a whole new kitchen! So it all depends on my budget nearer the build.

That did include the main concrete base as well so i could do that separately from the main trench foundation. I am still debating a timber framed structure which would be much easier. It just depends on how long it'd last and how much work would be needed to maintain it.
 
I went down that route... Decided it'd be far less arsing around to do it all in blocks.
AFAIK seeing as mine is purely a garage, not attached to the house, there are no specific rules under permitted development as to what the base should be.
I'm thinking 500mm trench with 360mm of concrete and 1 block to get it to ground level, a 2nd block to get it 215mm above, type 1 and a whacker plate, DPM up and over the first course of blocks then 150mm slab with rebar in it.
Single skin with 2 piers equispaced on each wall (5m x 6m)
3.5m hole in the front wall for a roller door, one in the side for a walkway and a pitched roof.
 
For a garage would you not need a thicker slab to accommodate the weight of a car?

Also why not just trench fill up to ground level? Is it better to do your way?
 
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