Exposed screed getting soaked!

[MDK 24]

Hello all - I built a new garden room on existing slab earlier this year which was not the same size and left some exposed concrete. I have since used a disc cutter and breaker to remove the exposed screed and jabbalite down to the concrete slab as suggested on here 6 months back. Since then not much has been done and we have had a lot of rain the last month! I have had a few people round to look at it, and main suggestion was removing bottom feather boards and fitting roof felt all the way round to the OSB and then torching it onto the concrete and over the old blockwork footing to prevent any water getting inside or on the concrete at all. I will then dig out all round the old blockwork and fill with shingle, and cover the torched felt with shingle to hide it. I have tried to draw it in a diagram with where the felt would go in the red line on photo attached.
My first question is can anyone confirm if this will be a good solution to the problem? Even if it only last a few years then I’ll probably knock it down and build a bigger one with a proper base! (Iv learnt my lesson)
Second question which is concerning me is that the exposed screed, jabbalite and concrete is getting soaked all the rain we have had recently and I worry it’s all soaking through underneath the building. Will this have made its way through all the floor? It’s about 4m by 3.5m. And will it be an issue if I fix it with felt while still damp?
To add - the room was carpeted and plastered in July and there has been no sign of any damp whatsoever so far. It’s only on the outside I can see it’s wet. But I do worry the longer I leave it it will start getting damp inside, so want to fix it now before winter. Any suggestions / comments much appreciated to stop me losing my mind any longer! Thanks

 

[robinbanks]

Your picture doesn't appear to contain a depiction of any jabbalite. What is the screed made of?

 

[MDK 24]

Thanks for the reply- Here is a pic showing the issue, so the jablite is between the screed and the concrete base. No idea what the screed is made of as I didn’t buy it or lay it…hopefully the pic shows. It feels solid but As you can see it’s wet and the jablite is soaked. Appreciate any suggestions!

 

[Mr Chibs]

Is there any DPM under the concrete slab do you know?

I see some under the wood bearers, so hopefully this will keep the base dry.
It also looks like there could be polystyrene under the screed, this will be a barrier to damp coming from the ground.

Perhaps you could paint a liquid DPM band all the way around the bottom, or flash band skirt, stapled on to the framework, tucked under the cladding.

I don't see what the problem is with the slab getting wet?

 

[MDK 24]

Hey - Thanks for the reply. When you say slab do you mean the concrete or the screed? Yes there was a blue sheet of DPM laid before the concrete was poured, then jablite and screed on top. Unfortunately that black membrane you see is something the chippy put in stapled up the OSB before cladding, it’s not underneath the wood bearers which is very frustrating. So my concern is the screed getting wet now and travelling up to the timber frame. I have a tin of black Jack and a roll of Bostik flash band so glad you agree that is a suitable solution! Then just need to either shingle or deck over to hide it all…..

 

[robinbanks]

Mmm, black jack will eventually wash away and Gashband is a bit.. er..

Think I'd use a waterpoofed and painted render all the way up and under the lowest cladding board or I'd clad it all the way down to the concrete

 

[MDK 24]

Waterproof render sounds interesting I hadn’t thought of that. Do you just mean up to the level of the screed? And yes cladding down further I considered but thought that isn’t going to stop the screed getting wet unless I put some membrane behind before cladding…. Or put a trim of 4 by 2 all the way round to neaten it up

 

[robinbanks]

The cladding should make for an adequate rain screen otherwise that OSB will soon be considerably worse for wear. I meant render over the screed and jab, so going from concrete slab up and behind the overlap of the lowest lap of the cladding..

 

[MDK 24]

Thanks will have a look into it. My main concern at the mo is whatever solution I choose since the screed and jab is soaked from all the rain we have had…. By putting a seal all the way round an I not going to be locking all that damp in? And then where would it go? Will it soak down through the concrete underneath or is it possible it could rise up? Thanks

 

[Notch7]

Thanks will have a look into it. My main concern at the mo is whatever solution I choose since the screed and jab is soaked from all the rain we have had…. By putting a seal all the way round an I not going to be locking all that damp in? And then where would it go? Will it soak down through the concrete underneath or is it possible it could rise up? Thanks

once we get to summer it will get dried out

I would personally look at EPDM -it might cost a bit, but its proper resilient stuff an seasier for a DIYer to deal with

if its only for a year or so then felt or even flash band.