Retrofitting a damp proof layer?

[Badger]

Hi guys, I'm currently experiencing the unmitigated joy of house hunting and have come across one that ticks pretty much all of the boxes - including a newly built double garage.

The only fly in the ointment is that I've just found out that, for whatever reason, the guy didn't have a damp proof layer put down and water is already climbing one of the walls.

It's got a tin roof that was dripping with condensation when I visited which I'd already planned to replace, so I'm willing to undertake some work, but is there any way to retrofit a damp proof layer that isn't going to cost an arm and a leg? I need the garage to be pretty dry for my lathe and hopefully a milling machine at some point, plus all the other stuff!

Ta in advance.

[Deleted]

Nov 18, 2019 20:22:54 GMT Badger said:

Hi guys, I'm currently experiencing the unmitigated joy of house hunting and have come across one that ticks pretty much all of the boxes - including a newly built double garage.

The only fly in the ointment is that I've just found out that, for whatever reason, the guy didn't have a damp proof layer put down and water is already climbing one of the walls.

It's got a tin roof that was dripping with condensation when I visited which I'd already planned to replace, so I'm willing to undertake some work, but is there any way to retrofit a damp proof layer that isn't going to cost an arm and a leg? I need the garage to be pretty dry for my lathe and hopefully a milling machine at some point, plus all the other stuff!

Ta in advance.

What type of construction is it ?

i.e.

Single skin brick

Brick & block with a cavity

Single skin block

[Darkspeed]

Have a look at chemical damp proof layer and damp proof layer injection - probably the easiest method - way back in time I did an installation of a slate damp proof layer into the front wall of some old house.

[Badger]

Nov 18, 2019 21:58:33 GMT @grumpynorthener said:

What type of construction is it ?

i.e.

Single skin brick

Brick & block with a cavity

Single skin block

Ah yes, that would be useful information wouldn't it? Whoops!

It appears to be single layer breeze block with external rendering. The floor is concrete and pretty rough - I'd assume there's no damp proofing under that either

I've had a quick look at the chemical injection but seems a bit good to be true? Has anyone got experience with it?

[jonsey]

The garage I’ve just fitted a new roof to has no membrane under the slab. It has no damp proof under the blocks ( the blocks are laid straight on the mud - no foundations. The outside walls are only painted and the ground level outside is level with the slab. It is dry inside now it has a new roof. Are you sure the water isn’t getting in elsewhere. Ground above floor level, gutters or roof leaking? I’m sure rising damp shouldn’t go above 1.2m.

[Deleted]

Nov 18, 2019 23:02:01 GMT Badger said:

Nov 18, 2019 21:58:33 GMT @grumpynorthener said:

What type of construction is it ?

i.e.

Single skin brick

Brick & block with a cavity

Single skin block

Ah yes, that would be useful information wouldn't it? Whoops!

It appears to be single layer breeze block with external rendering. The floor is concrete and pretty rough - I'd assume there's no damp proofing under that either

I've had a quick look at the chemical injection but seems a bit good to be true? Has anyone got experience with it?

That's going to be hard work - Ideally you need damp proof course membrane to go between the slab and first course of blocks - you might with a deep enough diamond blade on large angle grinder just be able to get through and cut a slot but probably only being able do it in 500mm lengths at a time - once the slot is cleaned out you can thread a dpc in and make good with mortar - I doubt if cavity injection will work that well on a single skin block wall - I have used this method a few times but only on cavity walls - probably some internet research might help you along with a chat to a local tool hire company to see if there is any clever masonry cutting kit out there that may help you - A backstop if you cannot do anything about installing a dpc would be to run a dehumidifier on a 24/7 basis to keep the damp out the air but this is far from an ideal solution

[norfolkshire]

Unless there is some outstanding reason to buy this property, walk away whilst you can. The situation you have outlined is going to be a huge money-pit to achieve anything like a suitable solution.

One option would be making an offer on the property, less the cost of dmolishing and rebuilding a properly constructed garage/workshop. Ask the seller if the work to build the present workshop was built in accordance to both planning and building regulations? Going by your description of the structure I would surmise that it has not.

'Caveat emptor' OR 'Buyer beware' as the saying goes.

[gtviva]

It does seem a bit strange to spend all that money on a newly built garage and "forget" the damp course? if your serious about the property make sure you give the main house a good check in case that's bodged up as well!

If there is no planning applied for the garage the searches will show that up

With the injection type damp course they do work but its injected into the bricks and not the course of mortar, don't know if it works with blocks though

[Badger]

Thanks for the replies guys, doesn't look so promising :/

jonsey, it's actually a mixture of condensation off the roof and rising from the floor I think. There's one corner inside which is especially damp, there's a big patch on the floor which also goes about 50-60cm up the wall.

Does anyone have any experience with tanking? Seems like it's the only option which may solve the issue without breaking the bank.

Unfortunately I'd already made an offer and had it accepted before I saw all this and asked the pertinent questions - the viewings before were in the dry. Paid the solicitors their first fee, but not 100% committed yet, trying to figure this out before going any further!

[jonsey]

It’s still not to late to bargain. When I bought my last house, I’d agreed the price and when I had a survey they said there was damp and some worm that needed treating. I got quotes and had the house price reduced by that amount.

But if the damp is just localised and there is no membrane anywhere it sounds like it may be a separate issue. You could spray foam the roof to stop the condensation. This time of year is generally the worst for condensation.

[Deleted]

Tanking can be done - there are a couple of systems - one is chemical where you apply a paint substance then a membrane that ideally terminates in to a brickwork / blockwork course - I have only ever used this system once on a new build - below ground retaining wall which then had a cavity wall built forward of it hence it went unseen - I doubt if this would work in your case - there is a liquid water proofer that can be added to a cement render and this is probably your best option - you could get a local plasterer to do this for you and if you came up the wall for say the first metre to a stop bead that's probably going to be your best cost effective solution and it does work I had a contact of mine with a block work inspection pit that filled with water via the walls and was cured utilising this method - other things that may help if you are going replace the roof is to use a pre insulated roofing sheet and ensure a decent overhang from the external blockwork - addition of a gutter will very much help has will ensuring that the slab is free draining around its perimeter by reducing the ground level and infilling with a loose pea gravel

[norfolkshire]

Nov 19, 2019 17:12:18 GMT gtviva said:

It does seem a bit strange to spend all that money on a newly built garage and "forget" the damp course? if your serious about the property make sure you give the main house a good check in case that's bodged up as well!

If there is no planning applied for the garage the searches will show that up

With the injection type damp course they do work but its injected into the bricks and not the course of mortar, don't know if it works with blocks though

Re the searches carried out on the property, if you do go ahead, not trusting certain individuals, make sure that you point whoever is supposed to do the searches in the right direction. Things like this have been shortcut in the past. After all it will be your money thyat could down the pan if not done properly. :-)

[cortinaman]

Hi Badger,

I have a bit of experience in this sort of thing as part of my job involves inspecting churches (different scale but same principles!) so I would suggest you take a look at the following:

1. Is the ground level higher than the floor of the garage particularly in the spot which is damp?
2. Are the gutters (if it has any) leaking, and is any water dripping from them in the damp area?
3. If it has gutters, is there a downpipe in the damp area and is it leaking or does it direct water against the wall rather than into a drain?
4. Is the garage in an exposed spot (on a hill, or with open ground to the south west) where rain could be blown against the walls or up under the eaves, under doors etc?
5. Is the condensation on the roof dripping particularly in the damp spot?

The damp you are describing doesn't sound like rising damp and I would be looking for the source elsewhere rather than spending money on treating the symptoms.

Tanking, which you mention, is only really needed if the ground level is above the floor level and you are holding back water under a bit of pressure - it doesn't sound like that is the case with this garage. To keep the floor dry, the simplest method would probably be to lay a thick polythene DPM (Damp Proof Membrane) over the concrete slab and then cast a new concrete slab or lay a screed over that. I would suggest an injected DPC is your best choice for the walls, and involves drilling holes at intervals and injecting a waterproofing liquid - it has been around for years and there are plenty of companies who do it, but the kit can be bought quite easily.

Just a thought on the planning permission side of things, while you are getting the searches done, I would suggest looking on the local authority's web-site as they will have all recent planning applications on line, so you would be able to see if planning permission was sought for the garage. It might have been done under permitted development in which case I would be asking the vendor for a Certificate of Lawfulness for the garage.

Hope that helps a bit, and good luck.

[legend]

What appears to be rising damp could be the condensation from the roof dropping onto the floor. I wouldn't freak out too much about the damp proof layer as houses were built for hundreds of years before they decided that damp proof was essential.

If the ground level is level with the floor you will have a problem, which you can fix by digging out around the edges, but it will take some time to dry out. Also look at where the gutters dump their load, and see if it just goes into the soil locally, diverting this may save it.

The current weather will expose all sorts of weaknesses so this is possibly a snapshot of it in it's worst state, however, finding a nicer property will probably be cheaper in the long term

[legend]

My downstairs bathroom has no damp proof layer, [old coalhouse] the quarry tiles were laid over whatever compacted aggregate stuff they thought was useful in 1903. I used an epoxy floor resin that was 2 pack and around £50, then tiled directly over the top and it's never shown any evidence of damp in the last 10 years, however, i did lower the ground level as far as reasonable. 

[joem83]

Nov 19, 2019 22:49:39 GMT jonsey said:

It’s still not to late to bargain. When I bought my last house, I’d agreed the price and when I had a survey they said there was damp and some worm that needed treating. I got quotes and had the house price reduced by that amount.

We did that when we sold our last house, garage wall was wonky - so we knocked price of having it rebuilt off
Also had to renegotiate on our current house as the wiring was shot (melted)
Until you exchange, your not tied into anything really.

[Badger]

Thanks for all the replies guys - I've decided to go ahead with the survey (a full building survey) and we'll see what it turns up. I'm not massively happy with the garage revelations, and came to the same conclusions regarding the implications for the rest of the property, but I'm going to proceed with caution.
I already knocked 2 grand off the asking price on my initial offer, but I'm tempted to lower it a bit more - especially if there's more wrong with the house. We'll see what transpires I guess!

[norfolkshire]

Nov 21, 2019 21:39:51 GMT Badger said:

Thanks for all the replies guys - I've decided to go ahead with the survey (a full building survey) and we'll see what it turns up. I'm not massively happy with the garage revelations, and came to the same conclusions regarding the implications for the rest of the property, but I'm going to proceed with caution.
I already knocked 2 grand off the asking price on my initial offer, but I'm tempted to lower it a bit more - especially if there's more wrong with the house. We'll see what transpires I guess!

I believe that you have made the right decision; at the end of the day the Building Surveyor (BS) has a responsibility to you, to identify all issues with the property; dependant what exactly you agreed with the BS as being within the scope of a full survey, anything that he misses and you ultimately discover, are at his cost, etc.... Just got to sit back and await the report. The report will be a bargaining tool for further reduction in the agreed price of the property. Best of luck.

[jonomisfit]

My house has a single skin brick utility room built on the back.

It had horrific damp when I moved in. Brick onto slab no dpc.

I bought a load of hydrophobic injectable damp proofing and put it it.

It worked brilliantly and theres been no damp since.

It was only cheap stuff so I was surprised how well it worked. May be an option for you.

[kevins]

Same here, our house is a 30's build with solid brick walls and no real dpc, just before we bought it it had a dpc injected into the walls with 25 year guarantee, 30 years later it's still dry as a bone.