Damp Proof Membrane

[Woodythepecker]

Before i install the panels on my workshop wall i want to put up some sort of damp proofing, but before i go out and buy it i need to know a little more about it.
For instance are there different grades/thicknesses? Can you just use polythene or is there a special product?

Do you tape it directly onto the wall or onto the battens which will hold the paneling?

Is there anything else i need to know or buy?

Any advice will be appreciated

Many thanks

Woody

 

[Anonymous]

WP i used the £12.99 stuff from wickes which is 1000 gauge (20m x 2.5m)i would staple it to the battens and taped over the top of the staples ,allow a 450mm overlap and tape both sides of the joint . As its in the walls you should not need anything in a heavier gauge .I left the top untaped to allow air to circulate and hopefully prevent condensation on the dpm .Most builds use whats called building paper for walls as it lets the wall breathe but 1 its expensive and 2 it tears real easy on the roll .

 

[Newbie_Neil]

Hi Woody

I also used the Wickes stuff. It's cheap and it works.

I did mine in exactly the same way as AP. I also used it to damp-proof my floor.

Cheers
Neil

 

[Woodythepecker]

I went to my local Wickes today but they have sold out of the type both of you got and they will not be getting anymore. They only had packs of 4mx4m for 10.99.

I then tried my local builders merchant who have 4mx25m packs at £29.99. I will try a few more sources tomorrow.

Many thanks

Woody

 

[Woodythepecker]

Since the business first started i really haven't had the time to put the dmp and panels up, but i am now going to start next weekend.

AB you stated that i should staple the dmp to the battens and then tape over the staples, but how do i protect the battens from the damp as they will be on the wrong side of the dmp and would surely start to rot?

Also you said that you left the top untaped to allow the air to circulate and hopefully prevent condensation. Should i also leave the bottom untaped so that the air can go in the bottom and out the top?
I do have about 12 white plastic air vents (about 10"x6") laying about and i was thinking about using these, but the only trouble is this would mean cutting a hole in the panels and the dmp behind it.

Regards

Woody

 

[ProShop]

WTP
When I used to do this for a living, It was always the rule to put the batons on top of the membrane when using plastic sheet so that the panels were not in contact with the membrane, and as mentioned in the previous posts we would always use building paper or underfelt (roofing type), but the paper would be on top of the batons. Although plastic sheet prevents condensation from coming through where you don't want it. It's down side is it encourages moisture to form on the plastic itself (we called it sweating) If this can't escape then it creates still damp air which in time rots things and it smells like.... well..er... damp, mouldy etc.

If the walls where very damp we would inject a DPC and then spray the walls with the liquid DPC. And also if the walls were single skin and porous we would also spay 2 coats on the outer wall, this method used to be specified by the various architects and local councils.
This is a very useful tip if dry lining a garage for example as you wouldn't need to use a DPC plastic sheet membrane on the walls.
Hope any of this helps.

 

[Woodythepecker]

John thank you for the info. Sadly i haven't got the equipment with which i could inject a DPC. Would it be expensive to get a pro in?

As for the DPM, i bought 2 rolls of 1000 gauge. Before i put it on the walls i need to get check one or two points.

After i tape the DPM onto the walls, i will be using 2"x2" battens to screw the panels onto. Would i be right in saying that to stop any moisture/condensation build up behind the panels i have to fix these battens on vertically to the wall so that the air can circulate up through the gap i leave between the bottom of the panels and the floor and out through a similar gap i leave at the top?
I had planed to put the battens across the walls but if i do this the battens themselves would stop the air circulating from top to bottom.

Obviously to fix the battens to the wall i will have to make a number of holes in the DPM and although these will only be small it will mean that some damp/moisture could get in behind the battens and maybe rot them. What can i do to stop this? Would squeezing some sort of silicone around the hole/screw before i tighten the screw up be any good?

I do not have any building paper. What is the function of it? Do i really need it? If so will i be able to get it from any building suppliers?

If you can think of any more hits or tips i would be grateful

Regards

Woody

 

[ProShop]

After i tape the DPM onto the walls, i will be using 2"x2" battens to screw the panels onto. Would i be right in saying that to stop any moisture/condensation build up behind the panels i have to fix these battens on vertically to the wall so that the air can circulate up through the gap i leave between the bottom of the panels and the floor and out through a similar gap i leave at the top?

Woody, yep you've got it, each of the batons ideally needs an airflow in between.

Obviously to fix the battens to the wall i will have to make a number of holes in the DPM and although these will only be small it will mean that some damp/moisture could get in behind the battens and maybe rot them. What can i do to stop this? Would squeezing some sort of silicone around the hole/screw before i tighten the screw up be any good?

Your getting good at this , what we used to do here was cut small pieces of the DPC material used in new building work at the foundation level (you've probably seen this stuff it's thick black plastic on a roll, it comes in various widths) and placed betwen the wall and the baton where the screww is going after you drill the hole and the screw makes such a small cut in the DPC it prevents the damp from coming through, I think your idea of the silicone would work, if you can get the silicone at the hole. But be mindful that silicone won't stick to anything that is wet or damp.

I do not have any building paper. What is the function of it? Do i really need it? If so will i be able to get it from any building suppliers?

The building paper is basically two thin pieces of brown paper with a very thin layer of bitumin and a fine string mesh sandwiched in between. (how they do this is amazing) It works very well, put it will be dearer than the plastic sheet material. All good builders merchants stock it or should have no problem getting it. It's purpose as you have probably guessed when I mentioned the word "bitumin" is to hold the damp back just like the plastic, but you don't get the sweating I mentioned earlier as it's more breathable.

On really bad walls we used to fit a skirting that allowed an airflow, simply by rebating the back of the extra thick skirting and put small grill panels at strategic points, and to all intends and purposes it just looked like a real good quality skirting.

What sort of boards are you going to use?

 

[Woodythepecker]

Cheers John, thanks for your help.

I am going to get stuck in at the weekend.

Regards

Woody