Robsco1 Posted February 12 Posted February 12 Hi All, I'm building a new detached garage to use as a workshop. The new footprint will be 3.8m x 7.4m and wants to be insulated for the occasional times it's in use - I have an infrared heater which worked reasonably well in a previous un-insulated single skin garage, so will probably use 2 of those at either ends. The overall build will probably be brick/block rendered to match the house design, with an insulated cavity, followed by another inner block wall, with ply over the top. This will be a workshop, so *probably* no cars. Question one: My first focus is the floor, firstly whether to go for a slab or footings plus slab - I think the soil is quite sandy where I am, so understand that a slab/raft may be better, rather than having to dig (and fill) down so far to get past the sand? Question two: I think putting rigid insulation on top of the concrete would make the most sense from a heating aspect, to save the concrete absorbing all the heat before giving any back into the room - especially as it won't be heated all the time. Would joists and a "thick" OSB floating floor be ok, or is there a risk of damp or anything else?
JohnMo Posted February 12 Posted February 12 8 minutes ago, Robsco1 said: rather than having to dig (and fill) down so far to get past the sand? Sand is good, pretty much self compacting, if I needed to dig down below it, our borehole was 34m of pure sand. We are built on top of a sand dune that is now inland 8 miles. 12 minutes ago, Robsco1 said: occasional times it's in use Don't waste your time or money on insulation, 100mm thick concrete slab, so it can take a car, even if you don't use for a car. Job done. Put a thermal top on or work harder. 1
Nickfromwales Posted February 12 Posted February 12 4 minutes ago, Robsco1 said: footings plus slab This is easy to execute, but not the best for your ground conditions maybe; you may have to put down much deeper strip foundations. 5 minutes ago, JohnMo said: Sand is good, pretty much self compacting, if I needed to dig down below it, our borehole was 34m of pure sand. We are built on top of a sand dune that is now inland 8 miles. Don't waste your time or money on insulation, 100mm thick concrete slab, so it can take a car, even if you don't use for a car. Job done. Put a thermal top on or work harder. +1
Robsco1 Posted February 13 Author Posted February 13 I must admit this insulation is making me nervous. I'm currently in a single skin garage with 1 infrared heater, and it's kinda bearable. Would you still insulate the roof and walls? but just not the floor? This could also turn into a workshop for the missus doing sewing or anything, so we want it to be very comfortable. Maybe the walls and roof is already overkill?
Alan Ambrose Posted February 13 Posted February 13 Yeah why not insulate it. Check out recent edition of Harry’s Garage on PV panels. He fesses up that he has UFH in there! I’m enough of a wuss that I may not go out there in the middle of winter and will put off the job till spring. Wall mounted blow heaters are good for getting the air temp up quick.
Nick Laslett Posted February 13 Posted February 13 (edited) @Robsco1, my garage is actually a full ICF build with an insulated foundation. I didn’t go so far as to put in UFH!!! I’m sure this made the garage much, much more expensive. But my only motivation at the time was to keep the superstructure construction as simple as possible. The garage and house were built at the same time, with the same crew and same materials. On concrete pour day the trucks just kept coming and the crew just moved the pump from the house to the garage. Most of my self build decisions have come down to simplifying a process. You can chase cost and quality, but my experience, in real life is that actual people and processes are the weak point. So whatever you save in a material decision could actually get wasted because the execution eats away at that saving. But an insulated, ICF garage might be going a bit far. 🙂 I appreciate that your circumstances are very different. Only you can answer the cost benefit analysis, but you are pretty much free to do whatever you want. I’ve only built the two foundations, but the process of constructing an insulated foundation is very straightforward, but it will be more expensive than just a regular raft. Edited February 13 by Nick Laslett 2
Robsco1 Posted February 13 Author Posted February 13 Money isn't the main concern, I'd just hate to get in there and regret not insulating the floor. If I were to insulate the floor, I was also considering that the insulation would be better above the concrete, so I'm not spending time/energy heating the slab before the insulation gets to do it's thing - especially when it's not heated 24/7. If the insulation were to go on top, perhaps with joists and an OSB floating floor, could this all still be done up to ground level? ie with the DPM holding everything in and coming up above ground level?
JohnMo Posted February 13 Posted February 13 2 minutes ago, Robsco1 said: insulation were to go on top, perhaps with joists and an OSB floating floor Then you end up with a garage that isn't and cannot be garage when you come to sell the house at any point in the future. Or when you get older you may want it to become a garage. 4 minutes ago, Robsco1 said: especially when it's not heated 24/7 So irrespective of insulation it's going to get cold in there. If you want it to be a less cold garage floor, get some old (or new) carpet.
Canski Posted February 13 Posted February 13 You can do all this then put a 3m wide uninsulated garage door in it. The rest seems to defeat the object of the exercise then. If the long term plan involves closing up the door opening then its worth it. Otherwise I personally don't see the point.
Nickfromwales Posted February 13 Posted February 13 1 hour ago, Robsco1 said: Money isn't the main concern, I'd just hate to get in there and regret not insulating the floor. If I were to insulate the floor, I was also considering that the insulation would be better above the concrete, so I'm not spending time/energy heating the slab before the insulation gets to do it's thing - especially when it's not heated 24/7. If the insulation were to go on top, perhaps with joists and an OSB floating floor, could this all still be done up to ground level? ie with the DPM holding everything in and coming up above ground level? Just make it a regular garage with slab over EPS insulation (or PIR from seconds&Co) and take the sting out of the floor with these? https://www.bigdug.co.uk/workshop-flooring-c348/flooring-mats-c402/garage-flooring-c20293/interlocking-floor-tiles-c20294/bigdug-essentials-interlocking-vinyl-floor-tiles-p14434/s65752 Fit a decent sectional (insulated) garage door and happy days. Heat with direct electric as you suggest and accept this is just a garage not a man cave.
Robsco1 Posted February 13 Author Posted February 13 35 minutes ago, Canski said: You can do all this then put a 3m wide uninsulated garage door in it It's safe to assume I wouldn't be doing this. The door will also be well insulated. The point is to create a nice warm workshop all year round - woodworking, 3D printing, electronics, etc. ie, not to do a half-arsed job and only insulate half of it and be kicking myself later on. 1
saveasteading Posted February 13 Posted February 13 I wouldn't insulate the floor. The heat loss around even an insulted and 'sealed' garage door is quite high. double glazed windows yes. If the roof is in cladding then add translucent sheets for free light and nicer ambience. heating by infra-red directed at the working areas. Perhaps one on a rig to move as required. Depending on what you will be doing, put a mat on the floor where you stand. Some of the above might change if you were to be in there for much of every day.
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