Laying an engineered floor...

[dormermike]

Hi

Sorry if this has all been asked before.

I am laying approx 55sqm of 18mm thick 190mm wide oak engineered flooring. 35sqm in a living room and the remainder in the hallway. The hallway is approx 8m long leading into the living room which is approx 7m long. Will be laying the boards lengthways along that 15m run.

I think I need to have an expansion gap at the threshold of the living room and hallway rather than run it right through, is that correct?

The living room is mostly level apart from near the edges where it dips approx 5mm over 50cm. I need to level that.

The living room concrete floor was laid in 1994 and has a DPM. Do I still need a DPM underlay or should I go with something else like fibreboard?

The hallway is circa 1930 so I need a DPM here. However one half of it is parquet blocks. Am considering laying the boards over the blocks with a non DPM underlay to allow the blocks to breath. Am I crazy?

Thanks a lot
Mike

 

[Doggit]

The parquet obviously hasn't shown any issues, so shouldn't need a DPM, and the blocks don't need to breathe. Whats' on the other half of the hallway, as that may need a DPM on that part. Do you have a damp meter that you can test it with though.

Yes, you need an expansion gap between the two rooms due to their length.

I'd go with fibreboard on top of the concrete, and possibly (although it's not needed) in the hallway if that keeps things level.

 

[dormermike]

Thanks

The hallways is parquet blocks on bitumen at one end, and cement / concrete and terrazzo type stuff at the end nearest the living room.

I was going to DPM the concrete / terrazzo end (sheet or liquid) and no DPM over the blocks because as you say they are not swollen or damp etc.

 

[Doggit]

I would imagine that the terrazo is dry as well, so shouldn't need the DPM

 

[dormermike]

Am I right in assuming even structural 18mm thick planks need standard tolerance beneath them - 3mm over 3m in all directions? I've just taken up the hall carpet and the floor whilst mostly dry (bit of damp near front door, easily sorted) the floor is undulating with 10mm gaps. It's an odd shape room being 8m long and 1m wide for 4m and then 2.2m wide for the remainder. Bit like an L shape.

 

[Doggit]

Engineered wood doesn't need as much of an exansion gap as normal hard wood does, and often says 1.5mm at each expansion point. So you may well get away with less that 3mm over 3m, obviously glued wood doesn't require the expansion gap, but I'd still be inclined to leave one. Is the undulations over the terazzo, in which case you'll need some feather edge self levelling compund to sort that out. Are you taking up the skirting boards, and then relaying them afterwards.

 

[chappers]

a decent underlay will give you a better feel to the floor I mostly use duralay, but it's not cheap, but is foil backed.
As to whether to fill the undulations. To be sure the answer is yes and as doggit says a feather edge SLC might be best if there are loads of local undulations. There are times you could get away without, for example with your 18mm flooring it wouldn't matter if you were laying across uniformly cupped floorboards or over the odd small dip. But the more uniform and even the subfloor the better finish you will have.

 

[dormermike]

OK thank you both.

I have asked a local contractor for a quote to lift the parquet and Ardex NA and level the area. It's approx 8sqm so I'm hoping it's not hugely expensive (any thoughts?). Reason being now I've lifted the carpet the parquet stinks of bitumen and I'd like to get shot of it. No signs of damp.

Have had a quote to latex level the terazzo area which is undulating but the chap cautioned that it wasn't really leveller but more to smooth the surface. 140 quid for 4sqm area and said it would be "better but not perfect". Hmm!

 

[Doggit]

If he's saying it won't be perfect, then consider doing it yourself. You find the high point, and start from there with a long level. Drill and plug holes in a sqaure pattern at about 500mm corners, and put in a screw and level it to the highest point. The use a latex self levelling compund that will feather edge, make it slightly wetter (but not to much). clean the surface and then paint with an acrylic primer, and then pour the levelling compound, and trowel level to the top of the screw heads.

And the same principle applies to the larger area, but you'll need to put down a liquid DPM where the bitumen comes away, and throw dry sand on it before it goes off; then put the levelling comppund down. You can do it in two stages, and do the actual levelling on the second stage.

 

[dormermike]

Hi I'm in the process of levelling and it's my first time so I wasn't sure how much to buy. I figured I'd do it in layers and build up rather than go too far.

I need to build up another 5mm in places. Should I prime this or just lay the new levelling compound over the already set levelling compound? Its setcrete rapidset 30.

Instructions don't say anything specific just to use primer on subfloor before laying. I guess the set levelling compound is now subfloor so I'd need to prime it?

Thanks!

 

[Doggit]

Use Wickes acrylic primer

 

[dormermike]

Use Wickes acrylic primer

I used that on the concrete sub floor already, are you saying I should use it on the SLC which has already set too? If so - thanks, will do!

 

[Doggit]

The same principle still applies, as you don't want the moisture sucked out too quickly, so it still needs to be apllied.

 

[dormermike]

Got it - thank you!!

 

[aveatry]

Sorry for the late response but what caught my eye is your dimensions as I too have a 7m long lounge and a similar hallway also with engineered oak and had the same dilemma but I did not use any thresholds and I also carried on into a separate dining room total 40 sq M with a shorter hall way to yours and I have had no issues over the past 5 years it has been done.
I removed the skirting and also made sure that the plaster was cut away to the brick to allow for the floor to expand behind the skirt to the brick.
The underlay was I think duralay -3mm thick beige coloured rubbery stuff- not cheap but neither was the floor !