How bad is NHL 3.5?

[Stevers]

Rebuilding the sides and arch over the builder's opening of my basement chimney breast with NHL 3.5 has transformed it from something damp, smelly and corrosive to something very pleasant to live with. The front was plastered in NHL 3.5 and that's dried out nicely too.

For anyone wondering, there's been a major change of plan. The cost and work involved in putting in a radiant gas fire, stone hearth, brick insert, and metal gather was starting to add up, so when a nice little ex-display Gazco stove came up on Ebay for collection from Exmouth, I was the only bidder at £300. I'll now just bring the back of the opening forward 6" or so using stone from my stone pile, and with a reasonable effort to pick out the old contaminated mortar, I am confident that using NHL 3.5 again, it too will dry out and make the opening into an attractive and reasonably honest fireplace for the room.

Off the record, I've been using Thistle One Coat on other parts of the room where it won't be a problem, and was struck by how gypsum plaster rusts steel tools!

 

[Lacan07]

In my humble opinion it is very easy to go down the rabbit hole on some of this stuff.

My stance has always been that a quality NHL 3.5 is a great improvement on cement based mortars and renders for any property that isn’t constructed from concrete block work, and then from there you are into diminishing returns on further “betterment” in flexibility and breathability by using NHL 2 and again vs lime putty, against which you have to trade off increased labour, duration of works, potentially less availability of materials/skills etc

If time and money are no object then specialists doing hot lime work are brilliant, but you tend not to see that outside of large scale conservation works for those very reasons

Yes, I absolutely agree Twig, it's very easy to slide down that rabbit hole, whether it be the damp proof industry on one side or the lime plastering purists on the other I think its always important to remind people that life is often a compromise.

The only thing I would say is that, outside of the lime specialists which many of us can't afford, you do now have a choice when it comes to 'ready mix' lime. Most places, like the Lime Centre near me in Winchester, do both NHL and lime putty based plasters & mortars.

 

[overlander matt]

In my humble opinion it is very easy to go down the rabbit hole on some of this stuff.

My stance has always been that a quality NHL 3.5 is a great improvement on cement based mortars and renders for any property that isn’t constructed from concrete block work, and then from there you are into diminishing returns on further “betterment” in flexibility and breathability by using NHL 2 and again vs lime putty, against which you have to trade off increased labour, duration of works, potentially less availability of materials/skills etc

If time and money are no object then specialists doing hot lime work are brilliant, but you tend not to see that outside of large scale conservation works for those very reasons

I fully agree. We simply could not have afforded any other route than the bagged NHL approach on our place repointing the whole building, rebuilding and pointing boundary walls, replastering internally... It's nowhere near as hard as the cement we've removed from internal walls.