Building a workshop in an old stone built barn

[Jameshow]

I have a damp workshop if it really rains the floor slab becomes damp, however my tools haven't gone rusty probably because there is a decent amount of timber / shavings hanging around to absorb it....

Not that I do any fine work!

 

[MikeJhn]

Thanks for your advice. Do you have issues in your workshop with rusting tools?

I use Liberon wax on the cast iron beds of some of the machines, but other tools are in drawers and cupboards and seem not to mind, but this is a draft'y barn and I think most of the moisture is blown out the gaps under the doors, its also two stories high so any moisture in the atmosphere probably ends up above and goes out through the roof membrane under the tiles, to be honest I would not bother to try and solve a problem you don't know you have yet.

 

[MARK.B.]

Don't, we've all been there at some point.

Some people would say that i have never got past that point

 

[Jonm]

I have only scanned through this. Looking at the roof and general construction, it looks like a lot of work and cost to get the structure thermally insulated, plus there are lots of issues with damp. I cannot see the point of thermally insulating the floor if the rest of the structure is not being insulated, all it will do is reduce airflow around the timber in the floor.

Personally I would just put in a timber floor, say 4x2 joists with brick/tile supports from the floor and dpm between joists and supports. I would want plenty of air circulation so leave a gap of say 30mm minimum between floor and wall, minimum 50 mm gap between floor and joists. Lots of preservative on the joists. Probably a dpm over the joists to keep the moisture out of the flooring. Flooring grade chipboard is fairly resistant to moisture so would probably be ok. I would put in some liftable traps so the joists can be inspected/spray treated. Screw the floor down with non rusting screws and do not glue the flooring down or together. Then the floor can be lifted to replace/repair joists if they rot. I am sure someone on here could advise on the timber to use for the joists.

Idea of prices, today I priced a small quantity of flooring, floorboards 145x20 £5.45 per m, 22mm chipboard flooring 1.2m by 2.4m £23 each, both incl vat.

If you do want a fully insulated workshop with heating then I think you need a fully costed design with tanking of walls and floor. That would destroy the character of the barn interior and I suspect the costs would be high.

As others have said, working guttering.

Some more photos, particularly outside would help.

 

[Jameshow]

If you are only there for a limited time. ...

Make it removable and you have the basis of a workshop minus the cladding and roofing sheets.

 

[MCTWoodwork]

Rust.

I have a small stone shed with a thatched roof, it's good for the mower and mixer, but rubbish for woodworking tools.

The thatched roof keeps it dry and is its saving grace and it doesn't have soil banked up against it, but it's still a palace of condensation.

View attachment 141327

I can see why you produce excellent woodwork and carvings Adam living in a period property, loads of inspiration! You must be living the dream!

 

[johna.clements]

Ah, OK.

TBH, digging out the back wall would be tricky. The main access track is right behind the shed, and about 4' higher than the floor of the shed. On the other side of the track there's rock. I suspect that digging out the wall would mean repositioning the track, which would mean digging out all the rock. And getting a digger in there (4km along a very narrow and steep 4x4 track) wouldn't be cheap!

I would not be surprised if the rock continues under the track to the barn. It could well be that the stones in the barn wall are just facework to the rock. That could explain where the boulder comes from.

I would be tempted to hand dig one or two trial holes against the wall of the barn up to 500mm deep.

Some pictures would be good.

 

[Jonm]

Some pictures would be good.

Agreed, we are trying to help but with very limited information.

 

[Ollie78]

My workshop is inside a barn, though a more modern one made of blockwork and tin with a cement board roof.

The previous tennant had basically built an insulated workshop inside the exterior structure levelled the floor on large joists then studwork, celotex, osb quite a lot of windows.
Recently I extended this with 2 rooms upstairs, I made my bit with sort of home made sips panels 11mm osb, 45*95 frame with 100mm rockwool, 11mm osb.
I chucked 160mm of rockwool on the top and it works well.
Max temp in the outer barn 42.8 C max inside the structure 29 C so not bad.

I would suggest adding a breathable membrane if worried about damp but in my case the roof is good and there is air circulation around the outside so I didn`t bother with it.
Just sort of ignore the outer building and build one inside it.

Ollie

 

[David66]

Agreed, we are trying to help but with very limited information.

Visiting this weekend. Will take more pictures

 

[David66]

Some more pictures of the shed.

The front.

The back. As you can see, the ground level at the back, is higher than the floor of the shed. There was a discussion about digging a trench. it's hard to see with the ferns and all, but there are huge rocks up against the back wall, which would make digging the trench manually very hard, and getting a machine there very expensive.

This is stepping inside the door in the first picture, looking left. Generator, fire wood rack, temporary work bench. I don't plan to floor or wall this area.

This is in the same spot, looking right. This is the area I'm thinking about flooring and walling to create a work shop. It's hard to see but all the light comes in through translucent panels in the roof.

As you can see, the walls are not straight! Both the back wall and the front wall have "bulges".

The back wall is damp - not running with water, but the earth on the floor is damp.

The floor is rough cobbles and flagstones. It falls around 18" from the back wall to the front wall.

There is another "room" at the far end of the shed, through a doorway. I dont plan to do anything with this room.

So, that's it. Does this make any difference to the advice and thoughts above?

 

[Jonm]

That is quite some building, very interesting. Good photos. Filter drain outside looks a major undertaking and may not be possible if the rear wall is stone cladding to a rock face.

I see there are no gutters on the rear roof, normally I would suggest fitting gutters but there appears to be a whole hillside sloping towards this building so perhaps gutters would have minimal effect.

I think it depends how much money/time you want to spend. One way is as I suggested before, timber floor with air gap underneath and around the edges. Here is link to previous comment

Personally I would just put in a timber floor, say 4x2 joists

Here is a link to the trada tables which give joist spans for different timber sizes, joist spacing, loading and timber grade
Free UK Span Tables for Floor Joists, Ceiling Joists, Flat Roof Joists, Rafters, Purlins - Timber Beam Calculator personally I would go for smaller timber size and more supports. For shelving you could buy some stand alone shelving. If there is a howling gale through there it may need a stud wall faced with something moisture resistant, not ordinary plasterboard,

You mentioned heated workshop with wood burner. In that case it is insulated floor with insulated stud walls set away from the stone walls so air can circulate under the floor and up the gap between stone walls and stud walls and out the top. Then we get to the ceiling, you could take the studding up to the rafters then fit pir insulation to the underside of the rafters, ensuring that air can circulate between the rafters. Problem is the translucent sheet roof lights. No point in spending a lot of money on pir insulation and let loads of heat out of those. You could board over them with pir insulation or put some form of secondary glazing, maybe get some double glazed panels made and fit them in a simple frame. Or get some double glazed panels out of some second hand windows. You could always do a heating calculation and see what the heat loss would be without doing anything to the roof lights.

 

[David66]

That is quite some building, very interesting. Good photos. Filter drain outside looks a major undertaking and may not be possible if the rear wall is stone cladding to a rock face.

I see there are no gutters on the rear roof, normally I would suggest fitting gutters but there appears to be a whole hillside sloping towards this building so perhaps gutters would have minimal effect.

I think it depends how much money/time you want to spend. One way is as I suggested before, timber floor with air gap underneath and around the edges. Here is link to previous comment

Here is a link to the trada tables which give joist spans for different timber sizes, joist spacing, loading and timber grade
Free UK Span Tables for Floor Joists, Ceiling Joists, Flat Roof Joists, Rafters, Purlins - Timber Beam Calculator personally I would go for smaller timber size and more supports. For shelving you could buy some stand alone shelving. If there is a howling gale through there it may need a stud wall faced with something moisture resistant, not ordinary plasterboard,

You mentioned heated workshop with wood burner. In that case it is insulated floor with insulated stud walls set away from the stone walls so air can circulate under the floor and up the gap between stone walls and stud walls and out the top. Then we get to the ceiling, you could take the studding up to the rafters then fit pir insulation to the underside of the rafters, ensuring that air can circulate between the rafters. Problem is the translucent sheet roof lights. No point in spending a lot of money on pir insulation and let loads of heat out of those. You could board over them with pir insulation or put some form of secondary glazing, maybe get some double glazed panels made and fit them in a simple frame. Or get some double glazed panels out of some second hand windows. You could always do a heating calculation and see what the heat loss would be without doing anything to the roof lights.

Thanks Jonm. Appreciate you taking the time.

The decision really does seem to be to insulate or not to insulate. My concern is that, if I dont, there will be 3-4 months of the year that the workshop will just be too cold to work in.

Couple of questions - you say to fit PIR insulation to the underside of the rafters. How would you attach it? I had thought of nailing/screwing relative thin OSB to the underside of the rafters, and putting the PIR between the rafters, resting on the OSB.

On the roofing lights, what about something like this

https://clearambershop.com/products/axiome-opal-16mm-multiwall-polycarbonate-roofing-sheet
as secondary glazing? Looks cheaper and easier to fit than a double glazing unit.

 

[Jonm]

Putting the pir between the rafters is time consuming, you have to cut the pir with a saw to the correct width and push it in place making sure sure are no gaps next to the rafter, foam any gaps. It is time consuming and there is a lot of waste. If you cut it correctly you bash it in place and it stays there, if not diagonal screws in to rafter and seal with foam. Then you seal over the joint/timber with aluminium tape. you then have cold spots where the joists are. Modern approach is to put pir between the joists and a second pir say 50mm under the rafters. The only reason to do it is to minimise reduction in headroom but this is not an issue for you.

Putting the pir under the rafters would be much quicker, would eliminate cold spots at joist positions, cheaper as less wastage and allow air to circulate between the rafters. Fixing is simple, used these washers and long screws, then aluminium tape on the joints.
https://www.tcfixings.co.uk/product...6K8ef4FtOQ9D8etQvMyT093MOPdTYRnQaArLHEALw_wcB
As for overboarding, do you need that, you will have a surface which reflects light, why cover it over. If you overboard then long screws, 125mm and 150 plasterboard screws are available.
https://www.efixings.com/drywall-screws-125mm-and-150mm-long-fine-thread-sharp-point-zinc/
That polycarbonate sheet looks fine as long as it lets enough light through.

I will look out some photos of insulating between rafters that I did and post them

 

[Jameshow]

Thanks Jonm. Appreciate you taking the time.

The decision really does seem to be to insulate or not to insulate. My concern is that, if I dont, there will be 3-4 months of the year that the workshop will just be too cold to work in.

Couple of questions - you say to fit PIR insulation to the underside of the rafters. How would you attach it? I had thought of nailing/screwing relative thin OSB to the underside of the rafters, and putting the PIR between the rafters, resting on the OSB.

On the roofing lights, what about something like this

https://clearambershop.com/products/axiome-opal-16mm-multiwall-polycarbonate-roofing-sheet
as secondary glazing? Looks cheaper and easier to fit than a double glazing unit.

0r a 2x1 frame with two sheets of polythene bags either side DX bags for instance.

 

[johna.clements]

The main sources of water are, off the roof because there are no gutters, surface water and water running through the ground.

In the second picture the track appears to slope towards the camera. I would dig a shallow trench about 1m off the track, towards the barn, maybe 150 deep by 300 wide (shovel plus a bit). Tip the spoil on the the barn side of the trench to increase the "depth" of the trench. It will catch most of the surface water that leaves the track which could be most of the water that ends up against the barn wall. Make sure the trench does not have any ponds in it, always has a slight fall, it can wiggle a bit to get around rocks.

The ground water could be partly solved by the trench if the rock is up to the bottom of the trench and is not cracked. If the subsoil is sandy a trench could make the ground water worse, you would need to seal the bottom of the trench (maybe a thin layer of clay or concrete).

I would put on a gutter and run it to a water butt. Whilst it may not be the biggest source of water it would produce a free source of water.

 

[Jonm]

MI will look out some photos of insulating between rafters that I did and post them

This is my sons extension, I installed most of the insulation with some assistance, also did the building regs drawings and a lot of other work. This photo shows the insulation between the rafters, the sheets under the rafters, the washers and some taped joints. The void between the top of the insulation and the roofing underlay is vented at the eaves and ridge.

Just for info, here is the finished extension

 

[Adam W.]

That shed will collapse if you try to dig out the back.

 

[David66]

That shed will collapse if you try to dig out the back.

Dont worry, I have no intention of digging out the back. It would need way to much work to do by hand, and getting a digger in (4km along a very rough and steep 4x4 track), would be horribly expensive.

 

[Adam W.]

I can see why you produce excellent woodwork and carvings Adam living in a period property, loads of inspiration! You must be living the dream!

It's a crumbly dream and some may even describe it as a bit of a nightmare, but we've saved it from demolition and I'm happy with that. It's lovely and cool in the heat, which is nice as I melt easily.

Dont worry, I have no intention of digging out the back. It would need way to much work to do by hand, and getting a digger in (4km along a very rough and steep 4x4 track), would be horribly expensive.

That's saved you some work then.