Filling under one long side of window board

MichaelR

Hello,

I am trying to install a PVC window board. There is a new window installed. The wall is a single 9 inch block concrete wall, slabbed with insulated pasterboard (70mm insulation and 12mm plasterboard) inside.

I managed, more or less, to cut the right form out of PVC. I have also installed a wooden plank under the outer edge, screwed through to the concrete, so the plasterboard would not have to hold all the weight of the window board. I was planning to glue the PVC board on with Tec7.

But it turns out that the window board is tilted down towards the window. To make it even, I would need to put about 6 mm of *something* between the "far" (window) long edge of the window board and the top of the wall (which was concrete but some insulation was put onto it and then plastered).

But what do I put there, so it would reliably take the weight while not creating a space for damp and mold to accumulate? Another layer of the same PVC board would be too thick at 10 mm. I thought of cement, but not sure cement over plastered insulation is a good idea. I thought of a thin wood layer but that can easily rot if condensation happens. I thought of expanding foam but that won't hold the weight.

Or should I just let the board tilt towards the window?

whizbang

just use a €3 tube of cheapest acrylic filler. Tec7 is way over the top. What weight are you planning on putting on it ?

If its airtightness you are concerned about, its a whole new game.

MichaelR

Not airtightness at all. It's about providing all of 6 mm of height, under up to 10 kg of weight as there will be plant pots on the window board. Ar acrylic filler, or a layer of Tec7, will just get crushed by the board and go flat, I need something more solid.

Tec7 is what the board will be held in place with, I bought a bottle of Tec7 just so I don't have to do any drilling to attach it with screws.

RobbieMD

MichaelR wrote: »

Not airtightness at all. It's about providing all of 6 mm of height, under up to 10 kg of weight as there will be plant pots on the window board. Ar acrylic filler, or a layer of Tec7, will just get crushed by the board and go flat, I need something more solid.

Tec7 is what the board will be held in place with, I bought a bottle of Tec7 just so I don't have to do any drilling to attach it with screws.

I would've thought a strip of thin ply would do the job. If you're not happy with that, then some floor levelling compound could be used.

listermint

You just need plastic spacers. They can be got in any DIY store. They come in multiple sizes and can be stacked. Use them to level it out along the length.

And stick with the Tech7 as its permanent, any other cheap stuff will come up.

MichaelR

I would be too afraid of rot to use ply. Condensation can happen next to a window frame.

Floor leveling compound sounds great but is only sold in huge batches. I'll look out to see if I can get a wee bit off someone and will also ask around for plastic spacers. Thanks!