Terrace construction at house (with photo) - sealing, cutting?

Hello,
we want to build a terrace (5m wide along the wall, 3m long) onto our house. The plan is to construct the terrace with edging stones and in several layers (20cm of recycled concrete material as frost protection, 5cm gravel layer, and on top either terrace slabs or, even better, paving stones). I have two questions about this in the hope that someone can help me:

1. How do I design the transition (gap) between the house and the terrace? Initially, I would attach a dimpled membrane to the underside of the house, to which the recycled concrete material/gravel will adjoin. Because of the slope, I assume that in the end there will be a small gap between the terrace surface and the house wall, even if just a few centimeters. There I could then cut off the dimpled membrane so that it is no longer visible. But how do I prevent moisture from accumulating in the intermediate gap? The house has only a 30cm eaves overhang.

2. According to my area calculations, the 15 sqm terrace could be built using 50cm edging stones, corner edging stones with 25cm on each side, and paving stones measuring 20x10cm (laid in a block pattern or with cross joints), so that no single stone would have to be cut. However, this would mean laying stone by stone because the paving stones fit exactly, to the millimeter, into the 5x3m edging boundary. Now, according to my research, jointing sand is always filled into the joints of paving stones/terrace slabs at the end. So, should I simply calculate an extra +5cm on each side for the joints instead of 5x3m and thus build the terrace 3.05x5.05m, or is the joint already included in the size specification 20x10 for the paving stones?

Regarding point 1. -> For example, install an Aco drain channel, especially sensible with only 30cm roof overhang. This should of course then be connected to a drainage system.

Hi, thanks. So house wall>dimpled membrane>gutter>patio stones or something else in between?

20cm concrete recycling material as frost protection, 5cm gravel layer and on top either terrace slabs or, even better, paving stones)

That already sounds good. Basically, you can also take a few more cm of recycling material if the surroundings allow it. Definitely use gravel and not sand. It costs a few euros more, but the ants won’t carry it away from your property.

1. How do I design the transition (gap) between the house and the terrace? Initially, I would attach a dimpled membrane to the underside of the house, to which the concrete recycling material/gravel would then connect.

Personally, I wouldn’t have used a membrane here. What purpose should it serve? The wall won't get damaged by the recycling material.

Because of the slope, I assume that in the end there will be a small gap between the terrace surface and the house wall, even if only a few centimeters. There I could then cut off the dimpled membrane so that it is no longer visible. But how do I prevent moisture from accumulating in the intermediate gap? The house has only a 30cm roof overhang.

Without the dimpled membrane, in my opinion, the water will simply seep away. Because of the roof overhang, you could use a gutter. We didn’t do that either. Despite various heavy rain showers, nothing happened. Also, at my parents’ house, everything has been dry for 20 years without a gutter. I see no benefit in it, not to mention from an aesthetic perspective.

2. According to my area calculations, the 15 sqm terrace could be constructed using 50cm edging stones, corner edging stones with 25cm on each side, and paving stones measuring 20x10cm (laid in a block pattern or arranged with cross joints) so that not a single stone needs to be cut. However, this would mean that I lay stone by stone because the paving stones fit the 5x3m edging boundary exactly to the millimeter. Now, according to my research, jointing gravel should always be filled into the joints of the paving stones/terrace slabs at the end. Should I therefore simply add +5cm for the joints on each side instead of 5x3m and accordingly build the terrace 3.05x5.05m, or is the joint already included in the size specification 20x10 of the paving stones?

You can disregard your area calculation. The stones are not accurate to 0.1 cm. One has a small edge here and another on the other side. Do you really want to set borders? You could also use 9/11 cm granite stones and set them afterwards. That way you definitely save yourself the cuts.

danixf: thanks for the detailed answer!

I would have only chosen dimpled membrane because it is used almost everywhere, similar to a drainage channel. Regarding the drainage channel, as a layman, I also wondered whether it is really necessary. I would have assumed that the slope is sufficient for the rainwater, which could then seep away behind the terrace.

So, from your point of view, one could basically also build the terrace directly against the house wall without any intermediate layer? Would you close the resulting gap somehow? So far, I assume that this might possibly only develop over the years, since terrace and house wall are not firmly connected.

The small granite stones do not really appeal to me visually as a terrace surface. Would that be the only alternative? Otherwise, for terrace slabs or 20/10 paving stones you always have to set the edging stones and would therefore most likely always have to cut?

danixf: thanks for the detailed answer!

I would have only chosen dimpled membrane because it is seemingly used everywhere, similar to a drainage channel. Regarding the drainage channel, I also wondered, as a layperson, whether it is really necessary. I would have assumed that the slope alone is sufficient for the rainwater, which could then seep away behind the terrace.

So, from your point of view, one could basically build the terrace directly onto the house wall without any intermediate layer? Would you somehow seal the resulting gap? So far, I assume that this gap could possibly only form over the years since the terrace and house wall are not firmly connected.

Personally, I am not so fond of the small granite stones as a terrace covering in terms of looks. Would that be the only alternative? Otherwise, for terrace slabs or 20/10 pavers, you always have to set the edging stones and would therefore almost certainly have to cut?

I quote everything because individual quotes are annoying on the phone. Yes, exactly. Of course, you can install a channel. Personally, I didn’t do it and as mentioned, nothing happened. Neither with all my friends. But there are definitely stories where it went wrong.

Yes, you can place it directly against it. Which gap exactly? You place the stones directly against the wall, right? The tiny gap is simply filled with sand. You won’t see it later or just overlook it. Also, later you can just sand it again if something shifts there.

I mean the granite stones not as a covering but as an edging. You place your stones/slabs and then set the granite stones in concrete afterwards. That would be the easiest way to avoid cuts. Otherwise, you could start with edging stones on one side and set the missing sides shortly before finishing the terrace surface. Then you only have to calculate 5–15 cm and not several meters.

I attached a photo again regarding the edging.