Waterproof materials

[peweuk]

I have a single storey extension to which I am adding a second storey.

To place the joists for the new first floor, I have to remove a few tiles along the ridge of the current roof which means removing rows of some tiles either side of the ridge.

I need to temporarily protect (over the summer) the existing extension from water getting in through the untiled area when it rains.

I thought of covering the new joists with some sheets of 8x4 chipboard ( which I can get at about £4.00 a sheet as they are seconds - used but in perfect condition , just dirty) and then waterproofing them.

My question is, what material can I apply to stop the chipboard to waterproof it - preferably sprayable, but brushable would do - so it would last during the summer.

(The other benefit of paneling out the joists would be the availability of a 'temporary working area' at first floor level).

Anyone got any suggestions?

 

[big-all]

do not use chipboard it turns to wheetabix when wet

go for 12mm exterior ply and sheet it over with a tarpaulen but not a cheap woven one that will biodegrade in the sun

 

[Symptoms]

pew - if the cheepo sheets of chipboard are only going to be used for a short period then consider them as support for a tarpaulin (as per big-all's post). Forget about applying a waterproof treatment to the chipboard. If you're worried about the tarps flapping in the wind, or blowing-off in a gale, then fix (screw) some battens over the tarp - tile batts are very cheap (slope the batts down the roof fall so that the water will run off).

 

[peweuk]

if the cheepo sheets of chipboard are only going to be used for a short period then consider them as support for a tarpaulin (as per big-all's post)

They will only be temporary (that's why I want to keep the cost down).

The problem is the tarpaulin - the area to be covered is 6.7m x 5.2m, and I haven't come across a suitable tarp that will fit in one piece - and they are so expensive.

I guess I could use some polythene DPC sheet (like the stuff used as DPC under a slab) if I can find some wide enough - it's usually only 4m wide.

 

[Symptoms]

pew - polyethylene mesh tarp 9 x 6m £35, heavy duty same size £68, camo same size £30, plus lots of others including heavy canvas jobbies from Northern Tools. Selco do a woven tarp 7 x 5.4 for £20ish.

Yes you could use other sizes of tarps or plakka sheet - just overlap and batten down

 

[peweuk]

Thanks Symptoms

I looked at quite a few places and they were all a lot more expensive than Northerns.

That looks like the way to go.

Thanks again.

 

[peweuk]

I have just come across these at a new Toolstation they opened near me.

I wonder if these will be good enough to last over the summer.

Anyone tried these?

 

[big-all]

they are the woven ones i was warning you about after about 6 months they start to biodegrade and leak or at least the ones i use do so if you plan to take longer than 5 months expect them to possibly leak

 

[Symptoms]

As peweuk wrote: "... I need to temporarily protect (over the summer) ..." then I think even the cheapo ones might last. Even if pew has to leave the cheapos up a bit longer he could always get another cheapo to cover any leaks.