How To Stop My Playhouse Getting Damp? A Builder Explains…

A playhouse is perfect for backyard imagination and adventures, but not if it’s damp! The main risk is that a damp playhouse grows mold, or worse, triggers illness in one of your kids. The other risk is that the wood starts to rot, and then over time, loses structural integrity. Take it from me, I let the first playhouse we owned get damp, and ended up having to replace it well before I thought I would.

To stop your playhouse from getting damp, you need to stop water from the ground, the air and the sky. You have to ensure that there is no way for the moisture to rise from the ground. You’ll have to install vents for good airflow and insulate the walls. You’ll also want to check the roof for leaks. If needed, you can also use damp absorbers from the grocery store.

Given what I went through, let’s go through how to set up your playhouse, and then maintain it, so that it doesn’t get damp, moldy or rot. This article was written with the help of a builder from Montpelier, Vermont. This is one wet town, with almost as many rainy or snowy days in the year as sunny days.

Construct Your Playhouse With Damp Prevention Top Of Mind


If you are using a concrete slab, use 6 mil black construction film under the slab, before pouring the concrete. The heavy-duty plastic film acts as a vapor and moisture barrier. This is important because concrete acts like a giant sponge, and sucks water up from the ground. This water is then drawn up into the wood of the playhouse frame. If you have already poured the slab without the construction film underneath, just put it over the top instead. Just remember that it isn’t UV-resistant, so will break down over time. Try to cover it entirely with the playhouse.

If you are not using concrete, be sure to use a leveled 4” base of gravel topped with a small amount of coarse sand. This will help enormously with drainage, and prevent the wood bearers coming in direct contact with the earth


Elevated playhouses will need to be securely fastened to the ground. It’s likely that posts will be in contact with the earth, as well as being anchored in. Ensure that the wood playhouse you have is made of either cedar or pressure treated wood, both of which are moisture-resistant. Start by sealing the wood with a quality wood preserver. If you have the time and a bit of extra cash, put the posts in concrete rather than in direct contact with the earth. This will extend the life of the posts (and give a better anchor).


Ideally, you can insulate the walls, and this will make your playhouse more comfortable to be through the year. How far you go really depends how north you are, and how much rain/snow you are likely to get through the year. If you are building from scratch, then this is an easy addition under the cladding or weatherboard. I like to use fiberglass batts for insulation, but you can also look at silver-backed bubble wrap (lighter) or a spray foam system (comprehensive). You might even want to consider house paper or housewrap, which goes over the insulation and under the siding.


Any entrance to the playhouse can also allow water to enter. If it doesn’t have a way to dry easily, then it will build up moisture and dampness over time. Best not to let it in! Make sure the door fits well when closed. Put weather seal trim at the base of the door, and a self-adhesive weather seal rubber around the rest of the door jamb. Paint the doors with a wood treatment, such as a wood seal or quality paint to preserve the wood both internally and externally.


Moisture can build up over time, and can be cleared with good airflow. Ideally, the kids will be in and out of the playhouse, so the air will keep moving naturally. If you close it up for a period of time, having two static vents should help. You can put one on opposite sides to help move the air across. I’d absolutely recommend covering these vents with insect mesh. You don’t want a home for bugs in your playhouse!


Seal around the windows with a silicon or caulk. Heavy duty Perspex or glass is good. You’ll want to beware of condensation build up as the temperature changes, and having good insulation can help prevent this.


You need a pitched or sloped roof that the water can run off, and if possible, with a generous overhang so that the rain drops away from the base of the walls. Quite often, purchased playhouses use a roof of plywood with a covering of felt or asphalt/tarred paper. This doesn’t wear quite as well as galvanized steel or well-designed shingles. If you do use felt, check that any nail holes are well sealed with silicon or thick paint.

Exterior walls

Clear away any shrubs, branches or other plants. You don’t want anything that gets wet to be in constant contact with the playhouse.

Having these things in place will help your playhouse stay nice and dry from the get-go.

Troubleshooting And Fixing A Damp Playhouse

If you have an existing playhouse, and you notice it’s getting damp, then you’ll need to troubleshoot where the moisture or water is getting in, and what’s stopping it from drying out.

Use sunny days to help with drying out. Open up the windows and door to allow a good cross-flow of air.

Girl Walking With Teddy Near Cute Playhouse with No Damp


Check there are no obvious leaks by running a hose over it. If there are, you can apply wood preserver to shingles, a coat of membrane paint to galvanized steel or replace the felt or tarred paper. You might expect to replace the felt every few years if it is very exposed to the elements.

Remove any leaf litter build up, and cut back any branches that are touching.


Wood preserver should be used each year. If the playhouse is painted, then you can add a layer of clear sealant directly over the paint. If it is unpainted, you can use a stained color or clear, whatever you think will look in character. Without the wood preserver, it is likely the wood will deteriorate over the years.

Check around the perimeter to clear old organic matter, such as leaves and branches, away from the walls.


It’s quite fun to get your kids inside the playhouse to check for leaks whilst you spray your house against the door or window!

Again, a good coat of wood preserver should help keep the damp out of the wood. See if rain is getting in around the door jamb. You can add a weather seal strip to the bottom of the door, they make them for inward and opening doors. You can also add a self-adhesive strip of weather foam to the door jamb.


Some playhouses don’t have Perspex or glass, and are just open. For these, you want to be sure there are no branches coming in, and that the eaves are providing some sort of protection.

If there is glass or Perspex, ensure there are no holes, and that the frames are well sealed. You can add a bead of silicon on the outside around the frame if needed.


You want to keep rain and snow from getting in, but once it is sunny, you also need to let any build-up of moisture and humidity escape. Opening the door and windows can help. But also installing small static (ie, non-powered) vents can help with cross-flow of air. Depending on the size of your playhouse, you can also put holes in the eaves (called soffit holes).

Rising Damp

This is a bigger problem to fix after construction or installation. But if moisture is coming up from the ground, it will need to be done. You’ll end up with black mold otherwise, and that will make the kids sick. You may need to raise the playhouse and put bearers underneath, and even add gravel to help with drainage. In extreme circumstances, you’ll need to look at where you placed the playhouse, and move it to higher ground. Black construction film, good quality gravel drainage and level high ground is your friend here.

Soft furnishings and toys

If there is any chance of dampness in the playhouse, try to bring rugs, blankets, pillows and soft toys back into the main house each day. These cuddly favorites can prevent the wood drying out. They can also become a source of mold themselves. You don’t want to be the one who has to tell your child that they can no longer play with their favorite toy!

I hope these tips have helped. These should stop your playhouse getting damp, and if it has gotten damp, this should help you dry your playhouse out. Go forth kids, and enjoy Mission: Backyard Adventure!!

You May Also Like: