Substrate query

[emmalcolburn]

Hi all,

I'm planning to prepare my consevatory floor for tiling. the previous owner had laid decking down over joists. I don't have enough hight just to overboard these (with the UPVC doors opening into the room) so I was planning to remove the decking and board the joists. I've been reading a lot but can't really seem to find out exactly what I need to use.

Would 18mm marine ply surfice?

Thanks in advance.

Emma

 

[Ajax123]

Are he joists suspended or are the on a concrete slab?

 

[emmalcolburn]

Hiya, they are on a contrete slab.

 

[Dan]

Take the lot up and screed the floor then perhaps, then tile that. Might be a good chance to get some underfloor heating in there too perhaps.

What depth are the joists?

 

[emmalcolburn]

10cms
I'm only a DIYer so not sure that i could scree the concrete. Although underfloor heating would be good in the conservatory. Is screeing doable for an amatuer?

 

[emmalcolburn]

having looked it up I think I wouldn't be able to do that. Could you give me advice on whether the ply would work?
thank you!

 

[Ajax123]

Pl would be dangerous as you cannot guarantee against deflection. You would be better to take up the joists. Lay 40mm of insulation and then put a screed on top of it. Or alternatively 60mm of insulation and a flowing anhydrite screed. Both of which are sensible options. I guess being a conservatory it is quite small so the sand cement screed option would probably be the easiest for you to DIY.

 

[White Room]

What is the distance between each joist.....

 

[DHTiling]

Take up the decking and then post some pics of what you have, so we can see what you can see ..

No need to lay screeds.. there are easier ways..

 

[emmalcolburn]

Ok, I'll take a few up at the weekend and post the pictures

 

[emmalcolburn]

Hello!

Well I did take up the decking and the then the joists at the weekend. There is a near perfect concrete slab below so it seems like the best place to start - other than I am about 10 cms to low. I'd like to put in some insulation and possibly under floor heating. I was thinking then some underlay type boards covered by cement board then lay the electric heating system before tiling. Is this suitable or have I really now just got to get a man in????

Thanks

Emma

 

[Ajax123]

Hello!

Well I did take up the decking and the then the joists at the weekend. There is a near perfect concrete slab below so it seems like the best place to start - other than I am about 10 cms to low. I'd like to put in some insulation and possibly under floor heating. I was thinking then some underlay type boards covered by cement board then lay the electric heating system before tiling. Is this suitable or have I really now just got to get a man in????

Thanks

Emma

Good stuff. If you have a radiator circuit in the conservatory you could go for a water underfloor heating system at that depth if you wanted. You could either use a small area system kit with pump and manifold which would mean at leat getting an electrician in which you wold have to do for the cable system anyway. Alternatively you ould use a return temperature limiting valve from dannfoss and do it all yourself. I have just done this in my lounge. These are very easy to install and no real need to get a man in. Water systems are Cheaper to run and can act as the primary heat source where as electric in a conservatory might be a bit hit or miss as you need so much power to heat a Conservatory due to heat losses.
Can't see the point of cement boards. NOw you have a flat surface to work from you would be better to insulate then screed to give you a nice solid floor onto which you can tile.
Screeds wise I personally would go for 50 mm of king span kooltherm k3 insulation ( don't buy from b&q as they are expensive. Get from a local merchant. Then 50mm of flowing anhydrite screed (gbflow from creative impressions is ideal for small areas as it is bagged. You can also work at your own pace) as this is best for underfloor heating.

 

[emmalcolburn]

Thanks for the advice. I still think me doing the scree is beyond me (hence the suggestion of cement boards) but maybe I can get someone to do just that bit. its a largeish room (2.5m by 5.5m) so could be a challenge. Really appreciate your help Ajax123! :smilewinkgrin: