Solid Maple floor on contaminated concrete

[JamesBlonde]

I have 40m2 of 18mm solid maple flooring to install on a concrete subfloor which has previously had marley tiles stuck down, and left the black / bitumen residue on the floor. I think its fairly impractical to remove this residue due to the size of the floor and amount of dust created when I made an attempt at it (with a wire brush drill bit - it would take days / weeks to do!) - its also not an empty house!

The floor is fairly level across its full length / width except around the exterior edges where the floor clearly collapsed not long after construction in the early 60's. It also had a large gap where I removed a wall. I've sand / cement (or concrete in the thicker bits) levelled these, and then used a levelling compound on top, so its level but perhaps not perfect

The dpm / glue manufacturer (Mapei) have advised that to glue the floor using their products, I need to remove the adhesive. They haven't given any advice as to how to do it.

The flooring supplier (Floors2go) have advised that they do sell a solid wood floor underlay which they recommend for situations like this, and would exchange the glue / dpm for the underlay. However they don't have any at the Exeter branch, and - helpfully - they wont ask for it to be transferred from another store, so I would have to go collect from Wales or Birmingham - the F2G stores that do have it in stock. I'm not prepared to do that.

So how would you do it? Would you recommend stripping the concrete floor and gluing, or would you go for the underlay?

If stripping the floor, how would you do it as dust free (and quick and cheap) as possible?

If underlay, what underlay is best to use?? I understand that it has to be adhesive to stick the floor down on to (so that its not a floating floor). Apart from being harder to use (apparently), what are the disadvantages over gluing directly to the concrete?

Also, am I OK laying a floor approx 10m x 4m with only expansion gaps around the side?

 

[WoodYouLike]

What are the measurements of your maple floorboards?

 

[JamesBlonde]

the longest lengths are approx 760mm x 84mm x 18mm (including tongue on length and width).

If I did go down the underlay route, would it be worth putting any sort of insulating material / underlay underneath any sticky solid wood underlay?

 

[WoodYouLike]

Are you sure about the measurements? 76 x 84mm is almost square

 

[JamesBlonde]

My bad - meant 760mm! always get confused when mixing cm and mm!

 

[WoodYouLike]

OK, no worries - I'm always getting mixed up with inches and feet (not originating from here).
76 cm is too short and 85mm too narrow to even contemplate installing the floor floating.
Either you have to go down the route of having the underfloor 'shot-blasted' which if done by a proper company results in less dust and mess than when you sand a wood floor and then fully bond the wood strips with parquet adhesive or opt for Elastilon Strong self adhesive underlayment on top of a DPM sheet. The Elastilon Basic is not suited for this type of wood strips and be aware of copy-cats!

 

[JamesBlonde]

Thanks WoodYouLike! I think I'll go the Elastilon route as it'll be a lot less disruptive, although I can't seem to get their website to work??

I take it its not worth putting any kind of insulation underlay under the Elastilon? I'm also guessing from your DPM comment that the Elastilon doesn't act as a DPM in itself?

 

[WoodYouLike]

No, the Elastilon doesn't come with a DPM so you'll have to install one (sheets) first.

 

[HaydnExport]

Have you thought about hiring a concrete planner?

 

[JamesBlonde]

Yup, I did think about it, but at around about £300 all in for 2 days from HSS I simply can't afford it

 

[Jayluvit]

I am currently doing my kitchen floor after just buying my first house. I am laying porcelain tiles down but when preparing the floor and removing the Marley tiles it revealed the dreaded Bitumen.
Spoke to several companies including Mpai all came back with the same answer. "Get as much as the Bitumen off as you can".
How did I get round this? A 9" angle grinder with a diamond wheel. You may need several discs depending on floor coverage.
unfortunately this method does create a lot of dust and does take a lot of time but is quite effortless. You will need ear protectors, goggles, mask and gloves and a steady hand so as not to take too much of the concrete off under the bitumen.
Was hoping to find a quick fix method for bitumen but to no avail.

 

[JamesBlonde]

If I'm going down the Elastilon route, is it worth "dust-proofing" the floor with a 5-1 PVA solution?? It is very dusty and mucky in there, so I feel I need to do something!

 

[JamesBlonde]

To add to the last question, whilst the floor is flat / level, I have found a couple of areas where there is some uneaveness. These are around the doors (there is a slope up to the back door where someone has previously tried to fix a crack), and where I've demolished a wall and there is a slight difference across the remaining gap in one particular section (one section slopes up slightly to the ex-wall on one side)

I think I need to level the btt around the door, but as I'm no longer gluing the wood to the floor but using elastilon, is it worth chucking some hardboard down across the whole floor to provide a nice solid level base to work off on the rest of it?

 

[WoodYouLike]

You could use some thin hardboard 3mm, but be aware that sometimes when you think that levels it out in one part it creates problems - when the boards are laid - in other areas.

 

[JamesBlonde]

Another bone question or 2 I'm afraid - this one really is a cracker though!

I know I'm using an underlay rather than glue now, but obviously the underlay isn't fastened down to anything. Whats to stop it (or sections of it) moving around under the floor and taking sections of the floor with it??

Additionally, there is a slight step out to the patio which takes 2 rows of 2 of the longer floorboards perfectly. This is about 5mm higher than the rest of the floor. Obviously using underlay on this area will be pointless, as 4 planks really won't provide the weight to hold it all in place (I'd be able to pick it up!), so how would you deal with this?? Level it and create lots more work for yourself? What about expansion gaps?