Stopping water seepage under summer house

[83dons]

Hi I have a 6x5m summer house. When its wet water seems to seep in under the treated wooden boards the structure sits on (they sit on a large concrete base). This is also worse at the side with the double front doors. At the sides of the summer house there is a larger overhang so less water gets to the base although I might seal these too. I have installed awnings over all doors and windows. The base is 6-12 inches wider at any given point than the summer house so water can pool and likely seep in underneath. I considered using putty or something to seal the concrete base to the wooden slats the summer house sits on but I feel some sort of deflector attached to the bottom of the shed may be better that would take away any rain over the edge of the concrete base might be best. As I said this can be about 6-12 inches wider at any given point it varies as not perfect square. Can anyone suggest a solution that will be cost effective? I include a photo. It mainly shows the side of the summer house which isnt so bad due to overhang of the roof but a bit of the front which has little or no overhang so rain hits it easily.

 

 

Edited July 30 by 83dons

[Alan Ambrose]

Maybe some DPC strip sealed to the concrete and up the sides of the timber for 6-9 inches? Maybe something under that to create a fall away from the shed.

 

Does that french drain fill up when it rains? Know where it drains to? Is there some fall in the concrete outside the door? 

[Onoff]

3 minutes ago, 83dons said:

Can anyone suggest a solution that will be cost effective?

 

Make the base smaller I would. It's a problem that will never, ever go away.

 

Somebody handy with a bfo Stihl con saw. Then flash behind the bottom timber and down over the concrete. Any timber near the ground should be no closer than 150mm (the height an average raindrop bounces).

 

A forever problem otherwise.

[Onoff]

Just seen the edited/revised pics. You'll need to keep the French drain as I see the slab is level with the surrounding ground. Then paint the bottom two boards in something, say black bituminous paint. 

[83dons]

11 minutes ago, Alan Ambrose said:

Maybe some DPC strip sealed to the concrete and up the sides of the timber for 6-9 inches? Maybe something under that to create a fall away from the shed.

 

Does that french drain fill up when it rains? Know where it drains to? Is there some fall in the concrete outside the door? 

Hi I can only find the following is this what you mean? Its a little expensive to do the whole summer house. Type Z Cavistrap DPC fixing strip - DPC Products Direct

 

There are drains at the sides from the roofing and they go down the pip and out into the chuckies which are quite deep and sub soil underneath. There was no drain dug to link in to. The main point where I can feel dampness inside is under the front doors and the front and back sides have no roofing overhang so they need some attention I feel the most. The side concrete doesn't get too wet due to the overhang. It just has treated filler planks along the side as the weight bearing treated strips go horizontal to front and back. I think the one at the front isn't sitting flush to the concrete bases so its easy for water to get in under it at some points so that area definitely needs sealed.

[Alan Ambrose]

No, I mean these - v cheap - just crease at the angle between wall and slab:

 

https://www.screwfix.com/c/building-doors/damp-proof-courses/cat850234

 

Not sure what you make the shallow fall thing from, but I know they have shallow angle stuff for flat roofs.

[83dons]

11 minutes ago, Onoff said:

Just seen the edited/revised pics. You'll need to keep the French drain as I see the slab is level with the surrounding ground. Then paint the bottom two boards in something, say black bituminous paint. 

There is a ditch all the way round with sub base and gravel which i brought up to be level with the slab. Its where the slab meets the wooden treated bearers that I feel water can ingress. I didn't paint the bearers same as rest of the summer house as they were treated as opposed to untreated wood but I can do that. Also hard to paint them without the concrete too. I don't think I can trim the concrete as the gravel is filled now and the metal rebar went to the edges of the concrete so might be hard to cut anyway? To me the front and back sides are the main issue as the sides have a considerable overhang and concrete doesn't get that wet. I feel some sort of skirting overhanging from the bottom of the summer house across the width of the concrete would help but unsure how to do this cheaply/well. I dont really care if it looks bad as long as it helps keep the water out in winter months. Water seems to drain away at the back from the drains ok into the gravel no issues, its the water that may come in under the bearers and pool underneath the structure I'm more concerned with. The awnings I fitted to all windows and doors have helped water that was coming through their seals a lot.

[83dons]

5 minutes ago, Alan Ambrose said:

No, I mean these - v cheap - just crease at the angle between wall and slab:

 

https://www.screwfix.com/c/building-doors/damp-proof-courses/cat850234

 

Not sure what you make the shallow fall thing from, but I know they have shallow angle stuff for flat roofs.

Ah yes that is what I envisaged could pick as wide a one as they have. How best would I fit it to the timber 6-9 inches up so as to avoid water seeping down between the timber and the plastic? Does it need some sealant and nailed in or tacks? Sorry not a great DIY man but happy to have a go! Some sort of plastic triangle lengths under that to create a 45 degree angle or so away from the base of the summer house? Not sure where to start with that but can have a look round B & Q I guess!

Edited July 30 by 83dons

[oksleator]

Is the water coming from the roof? Could you install guttering, a water butt, and then have the water flow from the butt into a drain (or put it on your plants if you're planning on greening up the space)? 

[83dons]

1 minute ago, oksleator said:

Is the water coming from the roof? Could you install guttering, a water butt, and then have the water flow from the butt into a drain (or put it on your plants if you're planning on greening up the space)? 

No the roof is completely sound in over a year I haven't seen any water ingress. It also has drains that drain into the french drains at the back of the summer house. Its under the front patio doors mainly and front side I can feel the carpet tiles damp Iv put down inside after  heavy shower so I assume water is pooling on to of the concrete and under the floor boards getting in under the bearers which wont all be 100% flush to the concrete as it wasnt 100% flat and smooth. The front and back also dont have big overhangs of the roof so much more likely for water to hit the bottom part. The canopies, water deflector wooden strips and sealant in gaps have dealt with slight water ingress around the windows and top of the doors so its trying to prevent water getting in underneath now Im more concerned with.

[Alan Ambrose]

An electric stapler with stainless steel staples is an easy way. DPC is very thin so not sure you need sealant unless the planks are bumpy. The object isn't to keep 100% of the water out, 99.7% will do.

 

Probably fix to the slab with CT1 or similar and tuck down the edge of the slab (or start by tucking it down first).

 

I think for the bit near the door (or all around if you prefer) the thing to search for is 'tapered timber firring / tapered fillet / wedge strip / shim' etc.

Edited July 30 by Alan Ambrose

[83dons]

8 minutes ago, Alan Ambrose said:

An electric stapler with stainless steel staples is an easy way. DPC is very thin so not sure you need sealant unless the planks are bumpy. The object isn't to keep 100% of the water out, 99.7% will do.

 

Probably fix to the slab with CT1 or similar and tuck down the edge of the slab (or start by tucking it down first).

 

I think for the bit near the door (or all around if you prefer) the thing to search for is 'tapered timber firring'.

Thanks yes stapler sounds a good idea, that's a lot of staples for a 22M perimeter!

 

Would the following sort of thing do underneath the whole way round, not sure it even need fasted to the walls I presume its only there to ensure against pooling in the plastic membrane and keep the angle there so the water drains off? Wickes Arris Rail - 75 x 75 x 100 x 2400mm | Wickes.co.uk

 

For the bottom of the door I think you can buy proper stormguards or even make one out of the triangle rail covered with the plastic membrane with an overhang so it goes over the edge of the concrete?

[Alan Ambrose]

Sound like you have concluded the design phase .

[83dons]

19 minutes ago, Alan Ambrose said:

Sound like you have concluded the design phase .

Thanks for your help.

 

My only thought is I aim to paint the structure every summer with the ronseal waterproof stuff it has on it. Doing this and the bottom board wont get painted again, which maybe is the one that needs it the most?! I guess it shouldn't matter if its pretty water tight. I guess I could maybe raise the membrane and paint underneath if I really want to but sounds like a nightmare!

 

Is it worth painting the bearers I didn't bother as they were supposed to be treated wood and couldn't be bothered masking the concrete to avoid painting it too.

Edited July 30 by 83dons