Blast room

[TorontoBuilder]

I'm designing and building a 161ft2 media blast room to be built on a friend's rural property so we will be able to media blast large equipment...

The first requirement is that it not require a permit. So it had to have a 15M footprint maximum within the exterior boundary.

The second requirement is that the space needs to be constructed very quickly, by the end of the building season.

The third requirement is for the space to be inexpensive to construct yet also durable.

The fourth requirement is that the space be large enough to store a Kubota tractor with attached loader to free up some garage space.

Based on the Kubota tractor dimensions and the desire to use a standard 8x7 garage door the space needed to be 105" x 194"

My friend has left over steel siding and left over steel roofing which is to our advantage. He was able to purchase a pallet of 2x4 dimensions grade 2 lumber at half price. So the framing will be 2x4. The roof will have 2x4 trusses that span 9.5'

The base will be 6" reinforced floating slab of 32 MPa concrete on a 6" base of compacted crushed granular material. There will be a 7.5" high curb of concrete masonry units with the cores filled with concrete. Rebars sections will anchor the curb to the slab and bolts set in the block cores anchor the walls to the curb.

I raised the heel height and eliminated an integrated footing after a couple of calculations proved the footing was overkill and the increased heel cost no more but improved the design in a couple of ways.

I was thinking of the beam install at the green point, next to the truss set. I have a couple of steel posts I can install to transfer the load to the foundation. Then I could hinge a panel at the ceiling so that it can be sloped out to direct errant media into the media hopper

The shed will have OSB siding on both the exterior and interior (not shown), but it has yet to be determined how to treat the interior walls. Is there a need/benefit for rubber coated walls, and if so what product will work but not cost too much.

Next question is should I build a beam at the mid-point of the shed that can support 750lb so as to avoid needing to use a gantry crane when blasting equipment?

I want to make a 8' x 2' wide media hopper that can sit on the floor, with the parts to be blasted suspended above so that much of the media is collected by the hopper. When not in use the media hopper can be hoisted up to the ceiling level. A back board can also be lowered so that it sits at an angle to direct media towards the hopper.

 

[phaxtris]

ive done a fair bit of blasting in closed in spaces, some things that come to mind...

you should plan on sheeting the interior, if you dont sheet it completely you will have media built up on everything and anything that is not both smooth and vertical, and it will be a mess for years to come, i know this from experience

reclaiming media is easily done with a broom and a shovel, it will absolutely not end up in your hopper, dont even bother, it will all need to be put through some kind of siev in any case before it can be re-used

some form for fresh air respirator is necessary

something to use to hang parts is a great idea, a couple laminated 2x12's or a steel beam could work depending on what kind of parts he is using

 

[TorontoBuilder]

ive done a fair bit of blasting in closed in spaces, some things that come to mind...

you should plan on sheeting the interior, if you dont sheet it completely you will have media built up on everything and anything that is not both smooth and vertical, and it will be a mess for years to come, i know this from experience

reclaiming media is easily done with a broom and a shovel, it will absolutely not end up in your hopper, dont even bother, it will all need to be put through some kind of siev in any case before it can be re-used

some form for fresh air respirator is necessary

something to use to hang parts is a great idea, a couple laminated 2x12's or a steel beam could work depending on what kind of parts he is using

Thanks for the advice re a hopper. Perhaps a shop vac and a cyclone may work?

Yes the interior will be completely finished everywhere. The ceiling lights will be in the attic behind clear panels.

The debate is whether or not drywall with a rubber coating will resist errant overspray.

I value my lungs and have enough respiratory issues so I'll be using a powered air purifying mask

 

[phaxtris]

You could use the shop vac and cyclone but putting it through a siev is a must, any large particles will jam the nozzle, real pita, that could be flakes from whatever your blasting, tiny gravel from your shoes, you name it, anything bigger than the media will ruin your day

I don't know about the rubber coating and drywall, I've never had to much of an issue with over spray, a guarantee would be metal of some kind, aluminum or steel, 22g or thinner wouldnt be to bad.....OSB painted with the smooth side in would probably be the cheapest

 

[JustaDB]

Damn. I read, "blast" and thought we were gonna blow stuff up...

 

[PaulL]

"media hopper"? So your friend has multiple streaming subscriptions and needs seats that fold out of the way to store the tractor. I'm confused as to the difficulty ;-)

 

[TorontoBuilder]

I guess we can just try painted osb to see how it goes.

I'll have to think about a separator system for the abrasives. Likely a blower with a variable speed motor rather than a vacuum so I can dial in volume and velocity using duct sizes and then tune the system so only particles the weight of the media should fall, and then a sieve in the top third of the media collection barrel

 

[TorontoBuilder]

"media hopper"? So your friend has multiple streaming subscriptions and needs seats that fold out of the way to store the tractor. I'm confused as to the difficulty ;-)

we really would like to make media collection as easy as possible so we dont have to have hundreds of pounds of media

 

[PaulL]

we really would like to make media collection as easy as possible so we dont have to have hundreds of pounds of media

(Was bad joke, in my world media is audio, video, etc. I assume you mean doing sand/pebble/husk blasting outside a cabinet. I guessI didn't even know that was a thing)

 

[Darren]

Headstones are etched via sandblasting with a rubber template in a blasting room. They have a glass divider wall with giant rubber gloves, just like a blast cabinet. No respirators needed. They shovel the media to recycle it. Go pay a local monument outfit a visit and ask to see their blasting room.

 

[Aarknoid]

May or may not be in the budget / plan ... but when Burlington adopted the 161sq' rule ...

pretty sure it comes in at 160

 

[TorontoBuilder]

May or may not be in the budget / plan ... but when Burlington adopted the 161sq' rule ... View attachment 51145pretty sure it comes in at 160View attachment 51146

That was my first thought, but it was not an option in this case. When I am able to move to the country it will be one of my first additions.

The property owner just built dream home and wood shop and wants to maintain the same aesthetic as the house. So same roof pitch and overhang, same siding, soffit and roofing material.

 

[CWret]

I like all of your plan.
But consider:
- having a door at both ends. This gives easy and great ventilation. Also if the sand pot is on wheels you can easily get it out of the way (roll it outside on good weather days)
- make the concrete slab extended outwards several feet at both doors.
- make the floor flat except for the extensions
- build in a very large exhaust fan in the attic with several ceiling intakes
- if you use the same building for painting, more lighting. Including recessed lighting on the walls.

 

[TorontoBuilder]

I like all of your plan.
But consider:
- having a door at both ends. This gives easy and great ventilation. Also if the sand pot is on wheels you can easily get it out of the way (roll it outside on good weather days)
- make the concrete slab extended outwards several feet at both doors.
- make the floor flat except for the extensions
- build in a very large exhaust fan in the attic with several ceiling intakes
- if you use the same building for painting, more lighting. Including recessed lighting on the walls.

Thanks for the great suggestions.

The floor will be flat with no slope, makes it easier, cheaper and less complicated to install masonry clock curb wall.

We're undecided on using the space to paint regularly, so the one time we plan to spray paint in it (lathe and a drill press) we'll use portable shop lights.

The double door idea is a good one but a non-starter for a couple of reasons. The shed is narrow, and with a wide door at each end there will not be sufficient cross bracings for the wind loads due to summer thunderstorms in the region. A man door at the opposite end would work though.

Another garage door adds $1000 to the construction costs which defeats the cost effective aspect of the project. The same applies to the extended slab. We went back and forth on that feature since is of benefit if you want to use a gantry crane right in front of the shed doors. We settled for no extension and perhaps we can add interlock at a later date after the gravel has compacted further and we can find cheap salvage interlock pavers..

As far as ventilation we have that covered in spades. I have specialized high static pressure blowers with ECM motors that can move close to 2000 cfm at 0.6 inches of water column. I'm designing folding exhaust intake hood for the area we will do most of the sand blasting. For a supply of fresh air we will leave the door open.

On nice days I think blasting outdoors is best which is why I thought a hopper would work to collect most abrasives. Instead I'm thinking a sheet of plywood with a 3mm rubber mat on it will allow for collection of media and prevent loss of media to the exterior. It is better than our initial thinking which was to just use walnut media and not try to reclaim it while using it outdoors.

 

[TorontoBuilder]

I like all of your plan.
But consider:
- having a door at both ends. This gives easy and great ventilation. Also if the sand pot is on wheels you can easily get it out of the way (roll it outside on good weather days)
- make the concrete slab extended outwards several feet at both doors.
- make the floor flat except for the extensions
- build in a very large exhaust fan in the attic with several ceiling intakes
- if you use the same building for painting, more lighting. Including recessed lighting on the walls.

Your comment got me thinking further... a used window can provide additional ventilation and lighting and is cheaper than a man door. Two used windows are still cheaper than a man door. The right sized window I can also stick a "blower door unit" into as well.

My bias limits my creativity as I age... that's a bad thing. Suggestions are a good thing.

 

[CWret]

In a previous life (well it seems like it) I had quite a bit of equipment and we did our own sandblasting and painting. We picked our days and did it outside. No nearby neighbours and behind a berm. We bought bagged sand by the skid. The guys were paid by the hour and it was not cost effective to try and salvage/reuse the media. New sand flows so much smoother and saves a lot of time. What size of compressor? For DIY’ers it is almost never big enough!

 

[TorontoBuilder]

In a previous life (well it seems like it) I had quite a bit of equipment and we did our own sandblasting and painting. We picked our days and did it outside. No nearby neighbours and behind a berm. We bought bagged sand by the skid. The guys were paid by the hour and it was not cost effective to try and salvage/reuse the media. New sand flows so much smoother and saves a lot of time. What size of compressor? For DIY’ers it is almost never big enough!

We have a upright 80 gallon compressor that just barely makes 20 cfm at about 90psi. But we have a 1/2 dozen mid sized compressors as well, so if we need we will cheat, and tee a manifold into the system to add additional compressors.

Yeah, the neighbour is a farmer so they wont care, but I am not keen on sand due to silica no matter how cheap since I already have respiratory issues.

 

[CWret]

but I am not keen on sand due to silica no matter how cheap

The guys used an air supplied full coverage blasting hood (canvas came over the top of the shoulders) - but sand (silica) dust is nasty. After using sand for about 5 years we switched to Black Beauty which works a little better than sand. It cost quite a bit more but is less than 1% silica. That was over 35 years ago that we switched to Black Beauty. The other reason for the big hood, big gloves, and a leather jacket was that our compressor was more than 10x the size of your compressors combined and was set at 120psi.
PS - the guys doing the blasting were over 6’2”, strong, young, and could easily handle the back pressure.

 

[TorontoBuilder]

The guys used an air supplied full coverage blasting hood (canvas came over the top of the shoulders) - but sand (silica) dust is nasty. After using sand for about 5 years we switched to Black Beauty which works a little better than sand. It cost quite a bit more but is less than 1% silica. That was over 35 years ago that we switched to Black Beauty. The other reason for the big hood, big gloves, and a leather jacket was that our compressor was more than 10x the size of your compressors combined and was set at 120psi.
PS - the guys doing the blasting were over 6’2”, strong, young, and could easily handle the back pressure.

It's nice when you are a commercial operation and can afford such things as supplied air.

 

[CWret]

nice when you are a commercial operation and can afford such things

Commercial yes, but small - my wife and I ran the business, we had 6 full time employees that sometimes mushroomed, for a short duration, to a dozen.
Sandblasting and painting was just a fill-in job. Our business was blasting not sandblasting.