Building a workshop in an old stone built barn

[David66]

As the title says, I plan to build a workshop in an old stone barn, and I need some advice/thoughts. I am inexperienced when it comes to building etc.

This is a picture of the current interior.

As you can see, it's rough stone, with a cobbled floor. The floor is very uneven, and drops about 18" from left to right in the picture. The wall bulges at the far left corner (where the boulder is - tried to move it, but can't !!). The roof is new, and sound, but there is water seeping in the left (back) wall, and the floor is damp.

I'm not looking for a liveable space (!), just somewhere I can set up a work bench, couple of saws and some storage on the walls.

Current plan is to drop studs from the rafters to the floor on each side of the barn, run a 4x2 along the bottom of the studs on each side, and then floor joists between the 4x2s - keeping everything as level as possible. Cover the floor joists with 18mm OSB, and the studs with 12mm OSB. So far, so simple, however, I have a few questions.

First, the floor joists will span around 3.6m, so will need supported on the (very uneven) floor - I was planning to use off cuts of 4x2 simply fixing the joists to the off cuts, and resting the off cuts on the floor/ground. Will that work? Alternatives? I plan to use treated timber, and paint anything touching the floor with bitumen paint.

Second, I'm worried about damp from the walls and the floor. Do I need a waterproof lining on the stone walls and the floor?

Finally, if I wanted to insulate (haven't decided yet, but will be pretty cold in winter if I don't) - what would be the best option (I rent the shed and the landlord doesn't want me spraying anything on the walls - so spray foam insulation won't work)?

Thanks a lot for your thoughts.

 

[Jameshow]

You could use offcuts perhaps make a t shaped foot to spread the load. Put some felt / slate under to stop damp.

You could put studs from the floor to the roof and insulation between. With these old buildings it's important to let them breath so leave a gap all round.

 

[David66]

You could use offcuts perhaps make a t shaped foot to spread the load. Put some felt / slate under to stop damp.

You could put studs from the floor to the roof and insulation between. With these old buildings it's important to let them breath so leave a gap all round.

When you say "felt" you mean the stuff you use on shed roofs? Any rule of thumb on the gap to leave?

 

[Jameshow]

When you say "felt" you mean the stuff you use on shed roofs? Any rule of thumb on the gap to leave?

Yes but bitumen paint will do just as well.

I'd use 4x2 studs and 2" insulation..

 

[Spectric]

That would be a great setting for traditional woodworking, one of those treadle lathes and a big stout bench.

I plan to use treated timber, and paint anything touching the floor with bitumen paint.

If it is that damp also use a DPM on the floor and bring it up the walls, might be an idea to look at semi tanking the building and keep everything off the walls so there is an air gap.

 

[David66]

That would be a great setting for traditional woodworking, one of those treadle lathes and a big stout bench.


If it is that damp also use a DPM on the floor and bring it up the walls, might be an idea to look at semi tanking the building and keep everything off the walls so there is an air gap.

Do I just lay the DPM on the ground under the raised floor, or do I attach it to the raised floor in some way?

 

[Spectric]

The DPM is to prevent moisture from the ground coming into contact with the floor or rising up, so I would lay it across the floor and partly up the wall to keep any ground damp from getting to your floor structure which I would not attach the DPM. How damp / wet are the walls ?

 

[mikej460]

I would first find out where the damp is coming from. If it's the roof then get that fixed, check to see if water run off is clearing all walls (use a powerful hose fixed at an angle to a stake to simulate rain). Buy a cheap moisture meter and check around the walls for water ingress then investigate how it's getting in (very often it's run-off from the roof or poor/missing guttering or earth banked on the outside). If you can't find anything obvious then you need to shield the walls and floor, effectively building a bubble inside the barn:
1. Fit a damp proof membrane 1200 gauge/300mu (cheapest is on eBay) and as stated above, buy sufficient to run it at least 300mm up each wall
2. Lay a timber joists supported by treated wooden legs each resting on a treated timber plate to spread the load.
2. As above build an internal timber frame wall out of 50mm battens between the rafters. Use more horizontal battens on the outside of the vertical ones to strengthen the structure. Staple Tyvek Housewrap all around the walls. This lets moisture out but not in. Make sure the 300mm of DPM is on the outside of the housewrap.
3, Then fix lengths of 3x2 or 4x3 treated timber from rafters to joists 50mm away from the battens/housewrap. These will support your tools/shelving. Nail/screw horizontal lengths (noggins) between each pair of studs to strengthen them. You could leave the new internal walls there or better still clad in OSB3 sheets screwed in to the new stud work.
4. Lay moisture resistant chipboard flooring over the joists
5. Fit PIR insulation in between the rafters and fill any gaps with insulating foam. Leave or clad in OSB3.

I think that's enough for now but once you've decided on a way forward do ask questions at each stage.

I hope this is useful

 

[David66]

The DPM is to prevent moisture from the ground coming into contact with the floor or rising up, so I would lay it across the floor and partly up the wall to keep any ground damp from getting to your floor structure which I would not attach the DPM. How damp / wet are the walls ?

They're not running with water, but there is green mould on the stone

 

[mikej460]

They're not running with water, but there is green mould on the stone

In which case if may be damp from the floor so you might be able to avoid the internal wall build and concentrate on joists raised on a DPM. Another solution would be to build a timber raft directly on top of the DPM.

 

[David66]

I would first find out where the damp is coming from. If it's the roof then get that fixed, check to see if water run off is clearing all walls (use a powerful hose fixed at an angle to a stake to simulate rain). Buy a cheap moisture meter and check around the walls for water ingress then investigate how it's getting in (very often it's run-off from the roof or poor/missing guttering or earth banked on the outside). If you can't find anything obvious then you need to shield the walls and floor, effectively building a bubble inside the barn:
1. Fit a damp proof membrane 1200 gauge/300mu (cheapest is on eBay) and as stated above, buy sufficient to run it at least 300mm up each wall
2. Lay a timber joists supported by treated wooden legs each resting on a treated timber plate to spread the load.
2. As above build an internal timber frame wall out of 50mm battens between the rafters. Use more horizontal battens on the outside of the vertical ones to strengthen the structure. Staple Tyvek Housewrap all around the walls. This lets moisture out but not in. Make sure the 300mm of DPM is on the outside of the housewrap.
3, Then fix lengths of 3x2 or 4x3 treated timber from rafters to joists 50mm away from the battens/housewrap. These will support your tools/shelving. Nail/screw horizontal lengths (noggins) between each pair of studs to strengthen them. You could leave the new internal walls there or better still clad in OSB3 sheets screwed in to the new stud work.
4. Lay moisture resistant chipboard flooring over the joists
5. Fit PIR insulation in between the rafters and fill any gaps with insulating foam. Leave or clad in OSB3.

I think that's enough for now but once you've decided on a way forward do ask questions at each stage.

I hope this is useful

Thank you. Very helpful.

The roof is sound. Recently replaced, and no sign of any water coming in during recent (very) heavy rain. It's only the back wall that's damp, and I'm pretty sure its earth banked up against that wall that's the problem.

Some follow up questions if I may

1. Does the DPM simply lie on the floor? Do you/how do you attach the 300mm to the wall?

2. When you say a treated timber plate, do you simply mean a piece of (say) treated 2x4, nailed to the upright support in a T shape?

3. So, there would be 2 internal frames - an outer frame against the wall, with Tyvek stapled to it, and the second one 50mm from the Tyvek? Do I attach the first timber frame to the wall, or just one end to the rafters with the other resting on the floor? Does it matter if the timber on the outer frame touches the wall?

4. If I were adding insulation to the walls, would it go between the studs on the 2nd or inner internal frame, before you attach the OSB? How would I fix it to the studs/noggins but at the same time, prevent it touching the Tyvek?

5, Do I need to insulate the floor? Presumably PIR sheets between the floor joists - again, how do you fix the PIR in place, before attaching the flooring - or do you just lay it on the floor?

3. What thickness of OSB would you suggested for the walls/floor/roof?

Apologies for all the questions ... I tend to over think things!!

 

[Sandyn]

That looks very like a very old worn out byre. The cows stood on the left, probably for milking. The channel on the floor is where all the cr@p was washed/brushed away.

You rent it and you are going to spend a considerable amount of money to make it usable? Any possibility you have your own place and space to build a new shed?

 

[mikej460]

I'd consider hiring a digger and digging out the earth and build a french drain behind the wall (basically a trench back filled with shingle). Answers to specific questions are:
1. Yes it just lays on top of the earth floor. You can staple the 300mm sides onto the back of the battens (facing the stone wall)
2. I'd use a square of 5x1 gravel board - it's only there to prevent damaging the dpm and/or the supports sinking
3. Yes there would be 2 internal frames but no you shouldn't attach it to the wall. The idea is to let air flow behind the housewrap to take away damp air.
4. Insulation would go in between the internal studwork not the battens. It shouldn't matter if it touches the housewrap but if you fit insulation you do need a vapour barrier on the inside of the studwork i.e. the workshop side, to stop damp air getting ito your work space. This could be stapled plastic sheet vapor barrier or OSB3 which is moisture proof.
5. If you can afford it then yes, as a cheaper alternative to PIR I've used polystyrene EPS70 slab to good effect in the past.
6. I'd recommend 11mm

 

[sawtooth-9]

Agree with Sandyn

 

[David66]

That looks very like a very old worn out byre. The cows stood on the left, probably for milking. The channel on the floor is where all the cr@p was washed/brushed away.

You rent it and you are going to spend a considerable amount of money to make it usable? Any possibility you have your own place and space to build a new shed?

An old Byre is exactly what it is. The main house is a renovated croft, attached to another old byre. I hear you on renting and the cost of renovation! It's a long story. The property is owned by a good friend. He's letting us stay there rent free, on condition that we finish the renovations he started 15 years ago! It's been a VERY steep learning curve!!! There's more to it .... but I won't trouble you all with the detail!

 

[TRITON]

Very nice, thats going to look the business when complete. Very traditional and woody.

 

[David66]

Very nice, thats going to look the business when complete, but I'll wager its going to be nippy come winter.

Agreed - beginning to think about a wood burning stove .... but I think I'm getting carried away!!

 

[TRITON]

I spent many years working in an unheated Butchers, and winters were cold to really cold.
Boss's advice if you're feeling the cold ...

Work harder

 

[mikej460]

An old Byre is exactly what it is. The main house is a renovated croft, attached to another old byre. I hear you on renting and the cost of renovation! It's a long story. The property is owned by a good friend. He's letting us stay there rent free, on condition that we finish the renovations he started 15 years ago! It's been a VERY steep learning curve!!! There's more to it .... but I won't trouble you all with the detail!

In a nutshell and as phase one I would:
1. Lay a DPM and floor
2. Insulate and board the roof
3. Dig out the soil behind the wall and lay a french drain

Then if you continue to have damp problems build the internal wall system I described.

If you can keep the lovely stone walls that would be a visual bonus but at the expense of useful wall space. There could be a middle ground where you could build a partial stud wall over a cruddy bit if there is one!

 

[David66]

If you can keep the lovely stone walls that would be a visual bonus but at the expense of useful wall space. There could be a middle ground where you could build a partial stud wall over a cruddy bit if there is one!

Interesting - so, build the stud wall on the back wall, where all the damp is, for shelving etc, while keeping the front wall as is