Garage conversion. damp proofing

[unwashed potato!]

anyone converted their garage or know about this?

been searching online for the options, but finding information from manufacturers more than real people so not trusting to advice given as they just want to sell their product.

we've a fairly decent sized garage that we want to split into 2 using breezeblocks, leaving the front 2/5 as a garage, and the rear 3/5 as an office space with rear french doors for access.

none of the walls are attached to anything, unfortunately, and it's single skinned, though the view from the outside isn't brick it's got a flat surface so had an extra layer of something on it. one wall will eventually become joining of the house once we do an extension in a couple of years.

i've looked at tacking, insulated plasterboard etc, but find conflicting views of what I actually need to do.

advice welcome. i can upload photos later when home

 

[unwashed potato!]

Nope nothing yet.

What were his costs?

 

[unwashed potato!]

epoxy paint the floor
stud walls in timber and insulate in between - you want at least 50mm PIR (50mm rockwool is not a lot) keep 20mm gap from original brick skin to prevent any themal/damp bridging
board the walls with plaster board
lay some rigid insulation boards on the floor and then a good thermal underlay
insulate the ceiling/roof as best you can depending on its construction.

thanks for this. would you not suggest doing anything on the current single skin brick? is tanking worth doing?

 

[unwashed potato!]

can you give a link to the epoxy we should look at?

The bottom 2/3 bricks are actually lower than highest point of the patio outside. one wall is 2 bricks, the other is 3 lower.

I've had a guy round that suggested something where we drill ever 10cm along the bricks and inject them to make them bone dry and that's all that's needed. ideally wanting this to be building regs standard as it looks like it'll cost more than i had first hoped.

 

[unwashed potato!]

thanks. i assume the air brick goes higher than the membrane?

 

[unwashed potato!]

Just an update with this. I'm looking to purchase some dpc injection cream to raise the dpc so that it's higher than the external ground. The stuff comes to about £70 all in. From permaguard

Then I was planning to get a dpm to go over all the walls, however I see the example above you don't go too high up the bricks. Would you suggest that anything say 3 bricks above ground or higher doesn't require the membrane? The dpm for all the walls was about £250 with all the bits needed from permaguard. Perhaps I can reduce this down and just do the first 4/5 bricks?

I would then stud it, put insulation (though unsure which to use) and then plaster board on top of that.

Finally insulation the ceiling I'm unsure yet what to do as I need to see what's above the current boards in place

 

[unwashed potato!]

@Marvt74
@Fairly sure the answer is no I don't think the dpc injection will add anything as long as the membrane comes up a several course of bricks and you add a couple of ventilation bricks.
I would use heavy membrane like https://www.fastbuildsupplies.co.uk/building-products/plastics-and-polythenes/damp-proof-membrane cheaper too

from what i understand, the injection is to stop damp being able to get any higher, which the membrane wouldn't stop, the membrane would stop the transfer from the brick to the inner wall/insulation. without the injection, if a brick near the bottom gets damp, the damp can then rise higher with nothing to prevent it getting worse.

 

[unwashed potato!]

2 of the walls are exposed externally, 1 is "external" but it's covered by a roof, and the other only 1 wall is internal.

1 of the external wall has soil on it up to about 5 bricks from the floor, well above the dpc.

The other external has patio about 3 bricks above the dpc

Is your advice above based on internal walls only?

 

[unwashed potato!]

@Fairly sure the answer is no

are the walls damp now?

i had 2 people do quotes, and both said the lower bricks are a tiny bit damp in one place, however they were sales men trying to sell so who knows. i guess one area might be but there was a blocked pipe outside which is now cleared so would need to double check

 

[unwashed potato!]

the guys i've spoke to and checking online suggests i don't need approval.

 

[unwashed potato!]

How would you know if the ceiling has asbestos?

I'm sure it doesn't, it's just a smooth chip board style ceiling or maybe plaster board, and I was about to take down but my partner put the seed of doubt in my mind and its grown.

 

[unwashed potato!]

met with the building regs guy today. he said as the garage isn't attached we don't need any building regs, though we can get them, they aren't required. saved us some money.

he did advise to do different to what i had planned.

he said to instead lay 1 brick, put a dpc, then another brick on top. on top of that a stud wall and insulate behind that creating a cavity.

then i think he said to then lay a dpm on top of that from the inside of the wall, and then build another wall on that, this to prvent mouisture from inside getting to the insulation

seemed an odd way to do it to me, plus i've bought dpm from permaguard so kind of planned to use that.

any thoughts from people on here?

 

[unwashed potato!]

I'm still unsure exactly what the best thing to do is. I've got some photos now and made a small bit of progress as I've removed the existing plasterboard ceiling and put the injection dpc in. Whether it's needed or not, the cost wasn't too much for me to do myself.

I've spoke to the guys who sold me the dpm and they suggested tanking the bricks below the dpc. Trouble is with paint on them I can't and I understand tanking isn't always a great idea.

In the photos any dark patches on the floor may be as there was a large wooden station with shelves here before and soiled spilled from potting happening before we bought the house. I've since cleaned the area and the water does pool towards the back left corner.

The wall with the shovel on is the one with neighbours soil about 3 bricks from the bottom in height. The others have the outside patio about 2 bricks from bottom.

If I put an air brick in the shovel wall, what position should it be roughly?

The plan I think I've decided is the follows.

Put an air brick on that rear shovel wall.

Lay 1 course of bricks spread out on the floor put the dpc sheet down and then lay another course of bricks on the original to create a gap below the dpc for air flow and allow the floor to be drilled into something.

Then put the egg shell style dpm I've got on all the wall going up to the ceiling.

Then timber drills onto that. Then insulate in between.

Then for the ceiling, figure out how to close up the gap that the plant is coming in (though perhaps air flow here isn't a bad thing?) then insulate the ceiling.

Should I lay a dpm between the layer above the ceiling and insulation, or between insulation and plasterboard, or not at all?

Then plasterboard everything and chip board the floor.

Any issues with this?

If I can ill try remove the soil from neighbours wall and apply blackjack to the lower part of the exterior wall.

Spoiler

 

[unwashed potato!]

Raised the dpc above ground level by 150mm. It was previously below and ground by 3 bricks in some places

 

[unwashed potato!]

what are peoples views on just laying thermal insulatoin slabs celotex style on the concrete and chipboard on top of that? so nothing actually screwed to the floor, just held down by gravity and the weight above?

considering this may be an easier option.

would i put the dpm below the insulation slab or above?

would 50mm be thick enough of something better?

any brands to look at as assume celotex for the most part you're paying for the name?