Problems with current shop

[woodsworth]

Well it's bad enough that anything put in close proximitry to the wall or on the floor it gets wet. I can't store wood against the wall or lean plywood up against the wall at all. I cut a kitchen and stacked it up against the wall so that when it was time to put them together i was a head of the game only to find out mould had decided to destroy almost every piece.

I dug even further after work today and found that there is two courses of blocks below grade. They are quite saturated. I also jack hammered a bit of the floor out to see what was in place for damp course and while there is some poly there it is thin old and degraded. so not much use as a damp course or membrane. The damp course between the blocks is above the concrete slab on the inside and was not folded down to create a continuous membrane.

So i think the damp is actually just coming straight in from the outside wall and into the slab.

 

[trousers]

Right.
The walls are on strip foundations and the slab has been cast afterwards with a lightweight poly membrane under it.
And there is a gap between floor level and the dpc in the walls.
So effectively damp will only enter in quantity via that gap, and especially if the outside ground level is too high.
The first thing is to get that ground level down, to at least below floor level. This will ensure that a lot less damp will be driven through the walls due to ground moisture retention.
I would then test to see how effective the floor membrane is by doing the test I mentioned before, but a little away from the walls. Even though the poly is thin it is probably still doing it's job (unless they damaged it when laying the concrete).
If the walls above the dpc are damp, due to rain penetration, then rendering or cladding the outside would be an answer.
The damp coming through the wall at floor level can be overcome, but may require you to think about attending to the whole floor at the same time to ensure a 100% result.
At the end of the day you are going to have to decide how much money to throw at this thing.

 

[woodsworth]

So effectively damp will only enter in quantity via that gap, and especially if the outside ground level is too high.

I won't be able to lower the grade the whole property slopes to the shop and as i said my partner wants a raised bed along that wall. This is why i introduced the idea of an exterior damp proofing to see what people thought.

However no one seems to think much of it at all. Is it people don't understand it or is there a problem with this form of damp proofing below grade?

In North America they bury houses 8 feet into the ground and waterproof the outsides of them in the same way i'm proposing. If there was some problem with it i think it would show up as flooded basements.

 

[Dibs-h]

In North America they bury houses 8 feet into the ground and waterproof the outsides of them in the same way i'm proposing. If there was some problem with it i think it would show up as flooded basements.

They do and they also wrap the bitumen with flat and dimpled membranes - lay ground drains (weeping tile) at the base of these walls. To just coat the walls and not protect them with membranes as Trousers stated they won't last for long.

If you read the data sheet on most of these products - they state that a membrane or protection board must be used. In your case a protection board would not be suitable.

 

[woodsworth]

What is the perforated drain pipe and gravel i'm back filling it with? I built houses in north America for approximately 20 years so i think i can say with confidence that what i'm suggesting is exactly how they build them there. The dimpled membrane is only extra insurance and is not necessary at all. I only ever seen that used on one house and that was because they built the foundation with insulated blocks filled with concrete. I understand if you are back filling with rubble that seems to be a norm here but i don't see that as suitable back fill and would be unthinkable in north america in fact you'd be told to dig it back up.

They use perferated pipe with good clean gravel and then it is either covered with building paper (a thin tar paper) or landscaping fabric and then back filled with a mixture of gravel and dirt.

I just want to make sure i'm not missing something here. i'll have the hole dug by the weekend and want to start painting it unless there is some very good reason that it shouldn't be done.

 

[Dibs-h]

What is the perforated drain pipe and gravel i'm back filling it with? I built houses in north America for approximately 20 years so i think i can say with confidence that what i'm suggesting is exactly how they build them there. The dimpled membrane is only extra insurance and is not necessary at all. I only ever seen that used on one house and that was because they built the foundation with insulated blocks filled with concrete. I understand if you are back filling with rubble that seems to be a norm here but i don't see that as suitable back fill and would be unthinkable in north america in fact you'd be told to dig it back up.

They use perferated pipe with good clean gravel and then it is either covered with building paper (a thin tar paper) or landscaping fabric and then back filled with a mixture of gravel and dirt.

I just want to make sure i'm not missing something here. i'll have the hole dug by the weekend and want to start painting it unless there is some very good reason that it shouldn't be done.

Land drain - Sorry comes from not reading posts fully.

I've seen the wraps and membranes on a fair few houses - almost all in cases where the original installation involved a bitumen
based paint only.

I think the membrane should be applied - Synthaprufe certainly do cover it in their data sheets and I don't think it is because backfilling with rubble is the norm. Their product (as with most) has very little abrasion resistance - IIRC. Also you can't just paint the stuff on - some data sheets mention that joints in brickwork\block work must be "levelled off" with a Vandex type product first.

Be a shame to finish only to have moisture creep back in - when the cost of the "insurance" product as you called it, is marginal in the grand scheme of things.

 

[trousers]

Re Synthaprufe. It may be useful to read the data/application sheet.
They use phrases like "should be protected....." etc.

How are you going to prevent the damp that is entering via a pathway up through the foundation blockwork to above floor level, and below the dpc in wall which is higher than the floor inside? And this pathway is also compromising your floor membrane.
It seems to me that without adressing this problem, all the external work will be of little value.

 

[woodsworth]

hmmm ok below grade i was antisipating filling all gaps with a thicker tar product I only know it as pitch, it has to be trowelled on after it is clean and dry. Then paint on at least two maybe three coats of bitumen paint. This will go all the way up to 8 inches above grade.

After this has set in a couple of days a shallow layer of gravel and then the perforated pipe will be rolled out and covered with about 6 inches to a foot of clean gravel. Then that will be covered with landscaping fabric. Oh and the trench is sloped so water does not sit. I am fortunate enough to have a sloping garden. they will be able to drain off unimpeded.

I know this doesn't make it water proof it only makes it damp proof.

above grade will be re rendering. I haven't looked into all the products available but i assume that i will be mixing it with some form of acrylic or similar product to make it water resistant.

SYNTHAPRUFE looks more like it is used for tanking. I think that would be excessive in this situation. I am only looking to divert most of the water. Next year i'll be working on pulling the existing floor out of the building and digging it all out and suspend a wood floor.

I have given a lot of thought to ventilating the shop space as well. This was brought up several times. I think for that i will make a HVAC unit, they are designed to exchange the air every three hours and are about 97% efficient for heat loss. the idea is to pipe inlets close to the floor and outlets in the ceiling. This way i can get air flow without loosing heat in the winter.

The ceiling will be sprayed with polyurethane insulation. It will be protected by framing a ceiling but i want to get all the pipes in for the HRV unit and dust collection before i close it all off. Probably not till next year though, budget is already stretched.

 

[trousers]

Re the bitumen paint. Check the data sheets. They don't like tar/pitch substrates, or excessively damp.

Next year i'll be working on pulling the existing floor out of the building and digging it all out and suspend a wood floor.

:shock:

Best of luck with that one.

 

[woodsworth]

Well i wouldn't even think about it if it wasn't in a state. It was poured in about 6 pours non of which are remotely flat or level. It is hard to even sweep it.

 

[chipchaser]

Hi Woodsworth,

If you haven't found someone to spray insulate your workshop it may be worth trying this firm:

www.foam-insulation.co.uk

If your walls and floor are structurally sound you might consider dry lining the walls using studwork with insulation and, if there is enough headroom to spare, screeding the floor to level it over a new dpm. I would expect that to be much less work than breaking up the old concrete, carting it away and making a new suspended floor. The aim would be to create a dry insulated box within the existing shell. I would consider laying the screed over a layer of insulation but the energy saving is not as great as can be achieved by insulating the roof and walls so the pay back period is longer.

Graham

Edit just tried the link and found it suspended earlier today! Telephone number is 0800 019 6064

 

[devonwoody]

Seeing that you have a very large workshop, perhaps you could section off a part and build a smaller insulated workshop internally which might solve your main problem and let the problem area remain for activities that are not so demanding with regard to the condensation issue.

 

[woodsworth]

Thanks guys, i've looked into spraying it is very expensive! I found kits that i can do it for under a £1000 and it is my hope to have that done by winter. I am also planning on building a stud wall inside. Although i will loose a bit of space it won't be that much considering the benefits of a warm dry place to work in the winter. That along with getting a combination machine i'll have the room i need to do kitchens and bigger projects that I just don't seem to have the room to do right now with all the tools in there right now.

Its money that is the issue really. Everything i make seems to be eaten up by maintaining current tools and buying tools to do the jobs i get. I haven't reached the break even point yet on this. Part of the problem is i'm doing things i really don't want to be doing but those seem to be where the money is right now. I'm renovating a cottage, i've gutted it, done the plumbing, plastered it built a fire place insulated the floor and am putting underfloor heating in it. Now i'm on installing a slate floor. It takes a lot of tools to be able to do all of these jobs and i'm constantly buying tools to keep up with the job.

I bought a belle 350 to cut the slate and the switch has gone on it and the blade is crap so now i'm buying a blade. I am also building some windows for a friend and have had to buy tools to do this. So much of my money goes back into this instead of gaining ground i'm supporting the business. I'm sure it is a tale most of you know already.

The shop is the most important part for me as i see this as a place where i'll be able to build the things i want and sell them, but it will take time to get it into shape enough that i'll be able to do this. It is coming though. I've dug a moat around it and am damp proofing it, installing a washroom and a drainage system around the building so that any water that does get there will be diverted instead of sucked up by the block work. Then i'll be able to build the internal stud work and spray the ceiling. I can use all the insulation sheets on the ceiling for the walls, so those won't be a waste.

Time and money! if only those were more available.

 

[devonwoody]

And looking at your avatar, you need a pneumatic nail gun as well. :wink:

 

[Thomasx]

Hi Woodsworth

Did you go for the xpandi-fom diy-kit? How did it work out?
I am thinking of using it to isolate our house that we are renovating, and I am interested in some feedback on how the xpandi-foam worked, how it was to handle, to spray etc.

Thanks,

Thomas

 

[Fromey]

This sounds almost exactly like my shed when I 'inherited' it after buying our house. It looks like it was build by a bunch of boy scouts with no prior experience of building even with meccano.

Anyway, I fixed the leaking rusting tin roof by ripping it off and putting in new tanalised joists then weatherproof ply then two layers of felt. I then discovered the condensation malarkey last year. However, I've now insulated with that double-foil bubble plastic stuff glued on to the inside ply surface. Hopefully that should fix it.

For the walls, I painted the entire outside of the shed with about three coats of Santex paint. I made sure I trowelled lots of paint into all the cement-block texture. For the brick skirt, I painted it with a clear waterseal. It's done a great job of drying out the shed (it used to get about a centimetre of standing water on the floor!) except for a section of wall where the neighbour's soil is too high (next job).

A slight sideways question here;

If I have waterproofed the external of the shed with breathable Santex paint (allows the moisture inside to get out), would it be a wise/unwise next step to Santex paint the inside of the shed?