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Concrete sectional garage workshop refurb - Work has begun.

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ManowarDave

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Hi all,

I'm after some advice/suggestions regarding making a nicer space to work in. I may also be a little bit jealous after following recent workshop builds by Sheptonphil and DBT85.

Currently my set up is in a double sectional concrete garage. I can hear the groans. Not my fault though, it came with the house. As a space it is great (about 4.8m x 6m). The biggest problem is in the winter with condensation. It literally rains inside. This spring I had to replace two work surfaces that have been water damaged and had to re-spruce up the cast iron. It's also cold enough to freeze the balls off a brass monkey!

I know the ultimate solution is to get rid and put something proper there. Unfortunately the budget will not stretch that far at this point in time.

My current working theory is to build a box within a box so the concrete outer effectively becomes my "cladding". Then I can insulate and board and have a happy space. I'll also wall in behind the up and over door for more wall real estate and reinstating the side door which is currently a poorly installed window with feather board badly installed below it. (When I say badly installed I mean that the previous owner actually fitted it upside down to catch and channel the water inside!)

The rest of the garage appears to be sound (if draughty) and apart from the condensation issues appears to be water tight. Construction wise, it sits on a pretty hefty concrete slab and is the type with vertical posts every 4ft and four overlapping horizontal slabs secured between each post. The roof sits on a metal frame work. It is corrugated cementitious asbestos, but again water tight for now so will be left well alone, to be replaced at a future date. It even has a brick walled inspection pit (also water tight)!

So, my thoughts so far are to effectively build backwards, starting with the existing outer walls in place, batten the inside to create an "air gap" against which a stud frame will be placed and fixed. The stud frame will then be filled with insulation (Kingspan or similar). Finally, board the interior with ply or OSB. The roof can then be done similarly I think.

We're about to have work start on a loft conversion in the next few weeks (hence the budget restrictions) so I'm hoping to gain the majority of the timber for the internal frame of the garage from what can be saved from the old roof on the house. In theory my only outlay should be the insulation and sheet materials.

Can anyone see any fundamental problems with this approach or suggest a better way of attacking this?

Thanks in advance.

Dave
 

Westwood

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Firstly apologies MD if my sixpennyworth is off beam as I don't know much about your budget and site.
I don't think there are problems with your approach but there may be a better way;)
If this were me , I'd be tempted to leave the concrete walls as they are and insulate and clad on the outside. But of course i don't know either a} whether your eaves detail can accommodate the extra width of this and b} whether you have easy access to all four faces of the building.
By insulating outside, you preserve all all of your internal space; going your route you are likely to lose up to 200mm off each "axis". I also wouldn't use Kingspan or Celotex or similar, but the much higher performing and easier to install Actis products. With this insulation, in a combination of their honeycomb Hybris product and the Boost R Hybrid multi foil stuff, you can achieve a U value the same as a newly built cavity wall construction, so you have a well insulated , and condensation free interior. And you still have your 4.8 by 6 metre internal space. I would clad this in something like Marley Cedral or Hardieplank as SheptonPhil has done, as your outer rain screen which then avoids having to redecorate in years to come. depending on your site and access , this again can be a DIY job.
Inside you then have a concrete wall to play with , ideal if you plan to have anything heavy like shelving etc hung from the walls. i have this and hung a 1200mm square heavy tool cabinet off the concrete inner walls of my solid block workshop, ex single car garage. With your approach you will need to know where all your studs are and even then, will you be comfortable if you have particularly heavy items to mountain the wall ?.
Perhaps there is a disadvantage with your approach in that your existing concrete wall will always be wet. Why not clad it on the outside, then it can dry out fully and you eliminate your condensation issue. Electrics and conduit may need to be surface mounted but most people are happy with that.
Actis insulation is used extensively in the building trade, particularly with timber frame construction. If you're not familiar with Actis, have a look at their website www.actisinsulation etc and they have many videos showing how you can install as a one man band, with none of the mess which goes with using sheet foam boards. Ideally you would insulate the inside of your roof too, and Hybris is ideal for this. If you plan to do this later it could be left until you do a decent job of the roof, get rid of the asbestos etc. The Hybris insulation is a simple friction fit between rafters or studs, and is a DiY option needing little or no specialist skills.
I have a 44mm thick walled timber shed roughly 4.5 by 5 metres, which has a basic roof of felt on 25mm boards, with rafters at about 600mm centres, and I'm shortly going to be overcladding this with felt shingles, and insulating the underside of the roof between the rafters with 90mm Hybris.
Hope this helps
 

MikeG.

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External insulation is great, but it always runs into problems at the eaves. Even if you have a decent eaves overhang, it is very difficult to get continuity with the roof insulation and still leave a ventilation path under the roof sheeting.

Dave, what's the inside of the roof like? Are you thinking of insulating at rafter level, or at joist (flat ceiling) level?

The fundamentals of what you are proposing are sound. However, there are some critical points you need to take into account. For a start, I wouldn't attach anything to the walls. I would suggest leaving a completely clear void, because you are going to need as much airflow behind your new inner wall as possible. I'd leave a 50mm gap, and use 4x2s to span from floor to ceiling. These MUST be lined on the inside (the workshop side) with a vapour barrier, but the good news is that OSB (or ply...not quite so good) acts as a perfectly good VB. Ideally, you'd sit the timber framed wall on a course or two of bricks. If you don't, then you should at the very least sit it on a very wide DPC which you then turn up the outside of your studs 4 or 6 inches in case any condensation does occur in the void. Your void can then be vented with airbricks (difficult to cut through the concrete), and at the eaves.

Come back to me on the roof, because the design is a bit different depending on where your insulation is going (rafter level or joist level).
 

SammyQ

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Dave, I have considerable sympathy for your cogitation; our housemove saw me shrink my woodworking space to a third of previous, to wit: into an uninsulated, draughty, 16' x 8',1950's sectional concrete panel single garage (how in Hades did people get out of their cars if they drove them in there?).
I've subsisted - woodworking wise - since (24 months), as I repaired and rebuilt our Bungalow-with-Bodgered-B*lls-ups back into "habitable", but I now (well, definitely before winter starts :cool:) want to re-floor and insulate The Hermitage.
What type of roofing do you have? Mine is asbestos/concrete sheeting, so is being left in situ, but the steels of the roof trusses are 4' apart and 4' wall-to-peak herzactly, so my "cunning plan" was to glue/fix half sheets of Celotex to their undersides. No other finish, save maybe spray white matt on 'em.
The floor will be rough 3"x2" or so, on top of a D.P.M., beefed up by extra 'timmer' here and there to take the weight of my 400lb Wadin saw and its heavier mortiser cousin, yada, yada, then chipboard recycled from an an incredibly complex and inept loft conversion. Debating what insulation to use down there, can't be 'floating' beneath floor as the surface is corrugated (think 1" deep corrugations) and subsided noticeably toward one end :( . Reckon individually cut oblongs of Celotex?
Walls are still 'out for tender' but, I am tempted to use the regular-spaced bolts of the existing panel structure as the anchoring basis for Vertical 'posts' 4' apart, with half-lapped squared 'frames' in between, secured to the posts, to which I fasten O.S.B. or similar on the workshop side. I am tempted, really tempted not to put insulatin behand that, but don't see how I can then expect to be cosy...costs ya'see.

That should give me a level floor that stops eating the wheels of my tool carts as I move them, have aerated ceiling and wall voids, and ward off the worst temperature plummets. Heating will be an 1.5kW oil-filled radiator.

Informed criticism welcome.

Sam
 

ManowarDave

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Thanks Westwood

I don't think external insulation is achievable in this scenario. Access to two walls externally is quite difficult. The garage is about 18 inches from the boundary on the rear and right hand side. The boundary at the rear is a wooden fence, the boundary on the right, another concrete sectional garage. I can just about squeeze in there once a year to cut back the brambles and ivy that come from the neighboring properties. Additionally the asbestos roof only over hangs the walls by a couple of inches to reach the guttering.

Mike,

The roof is pitched with the ridge running front to back. The current roof supports (are they rafters or trusses? I'll call them trusses for now and stand corrected later :) ) are of welded angle iron construction. There are no horizontal ties. They are bolted to the vertical posts between the concrete panels so the centres are approximately 1200mm. I would like to insulate to the "rafters" to maintain as much internal height as possible. The images below show the metal trusses. The bottom of the truss is approx 1.95m from the floor where it meets the wall so I would not want to put joists in at that level. I'm not the tallest person in the world but only 5" of head room across the whole area would get a little claustrophobic. The apex is about 2.65m from the floor, the underside of the truss at the apex about 2.45m



The trusses join at the apex with bolts.



Here is a brief drawing as a section through the garage.



As you can see in the photos there are more angle iron supports (three in total at about 1m centres) running the length of the roof perpendicular to the trusses which the roofing is fixed to. Will these provide enough support for insulation and boarding or will I need to add to this?
 

SammyQ

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Dave, I think you have the big brother of my one, judging by the similarity of the roof construction. Look forward to more on this.

S.
 

ManowarDave

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Hi Sammy,

They're lovely buildings aren't they? :rolleyes: I like the idea of using the existing bolt holes in the uprights to fix the frame to. However, having just popped out to the garage to take a look I think getting the original bolts out will be a chore. Lots of rust :). I think my garage may be a tad later that yours. PP records show about 1968 for mine.

An insulated floor sounds like a good idea too. Mine is "pretty" flat. Just slopes to the left a bit away from the inspection pit.

Dave
 

ManowarDave

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Hey Blister,

Was this the thread you were looking for?

 

MikeG.

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....... I like the idea of using the existing bolt holes in the uprights to fix the frame to.. ........
As I explained, I really wouldn't do that. You would then have to produce individual air inlets for each individual void you created, and that would turn into a nightmare. Mentally treat the inside of the concrete wall as though it were running with water.

-

Thanks for the photos and drawing. I think I would be tempted to put a flat ceiling structure across on top of the new wall frames, with OSB on the underside and mineral wool (fibreglass) insulation piled up on top. Getting the fibreglass in and held up before you install the OSB is the complicated bit, but battens and bits of string should see the job done. The point is not to leave a large void, but about a 50mm clear void to the underside of the roof sheet.......and, critically, to have that void continuous, unobstructed, and fully open at the eaves (with some insect mesh). That means you'll have more insulation in the middle than at the edges. If you leave a big void you'll probably need to install gable vents, which is why I would pile up the insulation.

The alternative of installing the insulation at rafter level (ie a vaulted ceiling) would be easier in terms of getting the insulation in, but much more difficult in terms of the structure. I can work this out for you if that's the path you choose to follow.
 
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Blister

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Hey Blister,

Was this the thread you were looking for?

Yes indeed , Thats the one , Thanks
 

ManowarDave

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Thanks Mike,

That makes sense about the wall void. Independent frame it is. Presumably this can be tied to the outer structure for stability at points (ie on stand offs) just not in continuous runs?

Instead of installing air bricks which would require cutting square chunks out of the concrete panels and mortaring in the air bricks, could I drill a hole pattern in the concrete to simulate the same?

I think I'd like to go down the route of the vaulted ceiling. Not only will it be less claustrophobic but will also give me some height to help turn/manipulate large panels and long lengths of timber. Any help in this area much appreciated.

Dave
 

MikeG.

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If you can get hold a diamond core drill, you could cut out some holes suitable for those cheap plastic circular soffit vents you see in modern eaves. Or, have a look and see if the infill panels can be lifted up. If you could raise the top 3 by say 15mm, leaving that sort of gap above the bottom one, you might be able to get some sort of insect mesh in there without compromising on the weathertightness. That's a theory only, as I certainly haven't tried it or seen it done.

You really shouldn't need to tie the timber inner wall to the concrete outer at all. I mean, a free standing workshop like mine is the same construction as you inner one is going to be, and it doesn't need tying to anything.

Let me know your eaves height and the roof angles and I'll look at the sort of structure that should work for you. Would a couple of horizontal ties at or just above plate level be a nuisance?
 

ManowarDave

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Hmm, I've got a set of core drills. That's not a bad idea at all. What's the odds I can't get a matching diameter though :). I think lifting the panels is too big a job. Despite my drawing the corrugated roof rests directly on the wall panels on the two side walls. I'd potentially have to raise the whole roof.

I was thinking the frame might need to be tied to the existing structure as there would potentially be no integrated roof structure to stabilise the top of the frame. I get what you mean having followed lots of build threads based on your plans and advice. Just stumped on how to apply it to what I have to work with.

A couple of horizontal ties wouldn't be the end of the world.

Please see the image below for additional dimensions. Let me know if you need anything else.



Thanks

Dave
 

Lons

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Ha, Core drills = 38, 52 and 115. Standard round soffit vent....70mm
Just drill a few holes and stick s/s insect mesh behind it with sikaflex or grab adhesive. You can buy it in rolls< I think mine is about 75mm wide, watch your fingers though it's sharp, don't ask how I know that. ;)

You already have ventilation at the join between walls and roof looking at the photo ( wouldn't that be enoughat the top Mike? ) That would also need insect proofing.
 

SammyQ

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"I think lifting the panels is too big a job. Despite my drawing the corrugated roof rests directly on the wall panels on the two side walls. I'd potentially have to raise the whole roof.

I was thinking the frame might need to be tied to the existing structure as there would potentially be no integrated roof structure to stabilise the top of the frame. "


As Dave says Mike, the horizontal wall panels rest on top of each other. Jacking up the wall would also mean jacking up the roof. Alternative Gents? The panels end on a flat horiontal surface, so the corrugations of the roof panelling naturally create exits up there. Mine are stuffed with War-Surplus bra padding (by the look of it) but insect mesh could easily be substituted. An angle grinder, subtly used(!!) could cut a few 'letterboxes' low down for those horizontal brick-replacement vents one can buy? This means one might cut to suit one's vent? Bingo, vented void behind internal panels. My pre-fab concrete panels are less than 50mm thick, so this should be possible, if tedious, dusty and a noise-abatement case in the making. Drilled holes at the corners (a la kitchen sink insertion ) should cut down the 'over-grind' lines on the panels, lessening repair/re-finish. In my wee huckster of a shack, the previous owner did exactly this, to put in two windows, post erection (behave!).

I agree with Dave'S second point too; any internal structure could be tied to the existing steels, by using longer bolts perhaps, with a lot of the load-bearing then being taken down to the floor (query? MikeG?). This would lessen or remove the need for head-height cross-ties, rafters, or whatever? [Non-architect/engineer perfectly prepared to be slapped down over this].

Sam
 
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